* Correspondence Stanley L. Marks, Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California, Davis, One Shields Avenue, Davis, CA 95616.
Email: ude.sivadcu@skramls ,
Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.
This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
The gastrointestinal (GI) mucosal barrier is continuously exposed to noxious toxins, reactive oxygen species, microbes, and drugs, leading to the development of inflammatory, erosive, and ultimately ulcerative lesions. This report offers a consensus opinion on the rational administration of GI protectants to dogs and cats, with an emphasis on proton pump inhibitors (PPIs), histamine type‐2 receptor antagonists (H2RAs), misoprostol, and sucralfate. These medications decrease gastric acidity or promote mucosal protective mechanisms, transforming the management of dyspepsia, peptic ulceration, and gastroesophageal reflux disease. In contrast to guidelines that have been established in people for the optimal treatment of gastroduodenal ulcers and gastroesophageal reflux disease, effective clinical dosages of antisecretory drugs have not been well established in the dog and cat to date. Similar to the situation in human medicine, practice of inappropriate prescription of acid suppressants is also commonplace in veterinary medicine. This report challenges the dogma and clinical practice of administering GI protectants for the routine management of gastritis, pancreatitis, hepatic disease, and renal disease in dogs and cats lacking additional risk factors for ulceration or concerns for GI bleeding. Judicious use of acid suppressants is warranted considering recent studies that have documented adverse effects of long‐term supplementation of PPIs in people and animals.
Keywords: acid, canine, feline, gastroesophageal reflux, histamine type‐2 receptor antagonist, misoprostol, proton pump inhibitor, sucralfate, ulcer
Ach gastric cholinergic neurons ANP atrial natriuretic peptide CKD chronic kidney disease DU duodenal ulcer EC enterochromaffin cells ECL enterochromaffin‐like cells GCN gastric cholinergic neurons GERD gastroesophageal reflux disease GI gastrointestinal GUE gastroduodenal ulceration and erosion GRP gastrin‐releasing peptide neurons H2RA histamine type‐2 receptor antagonist ICU intensive care unit IRIS international renal interest society ITP immune‐mediated thrombocytopenia MPT mean percentage time NAB nocturnal acid breakthrough NSAID non‐steroidal anti‐inflammatory drug PACAP pituitary adenylate‐cyclase activating peptide neurons PPI proton pump inhibitor RAH rebound acid hypersecretion RCT randomized controlled trial SST somatostatin SRI stress related injury SRMD stress‐related mucosal damage SUP stress ulcer prevention VIP vasoactive intestinal peptide neurons
Advances in the understanding of the regulation of gastric acid secretion have improved management of acid‐related disorders in people. Knowledge of the acid secretion regulatory mechanisms led to the development of histamine type‐2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) that have reformed the treatment of acid‐related disorders. The PPIs and H2RAs are extensively overprescribed in human primary and secondary care hospitals. Existing guidelines often are not followed.1, 2, 3, 4 A similar practice of inappropriate prescription of acid suppressants is commonplace in veterinary medicine. Judicious use of acid suppressants is warranted, considering recent studies documenting adverse effects of long‐term PPI supplementation in people and animals.1, 5, 6
The ability to accurately and noninvasively measure intragastric pH with catheter‐less radiotelemetric pH monitoring devices (Bravo pH monitoring system, Medtronic Inc., Minneapolis, MN) in recent years has advanced our understanding of the effects of acid suppressants and dosing protocols on intragastric pH in animals7, 8, 9, 10, 11, 12 and humans.13, 14 Unfortunately, critical assessment of acid suppressants in experimental models and dogs and cats with spontaneous disease is sparse, and most of the studies evaluating the efficacy of acid suppressants were performed in healthy animals.
The stomach is an active reservoir that stores, triturates, and slowly dispenses partially digested food into the intestine for further digestion and absorption, and also controls appetite and satiety.15 Its main secretory function is secretion of gastric acid,16 which initiates peptic hydrolysis of dietary proteins, liberates vitamin B12 from dietary protein, facilitates duodenal absorption of inorganic iron17 and calcium,18 stimulates pancreatic HCO3 − secretion via secretin release,19 suppresses antral gastrin release, and modulates the intestinal microbiome by killing microorganisms and preventing bacterial overgrowth.20 Comprehensive overviews of the regulation of gastric acid secretion (Supplement 1) and regulation of gastric mucosal barrier function (Supplement 2) are available in the Supporting Information.
Dogs have lower basal acid secretory rates but considerably higher peak gastric acid responses compared to humans,21, 22 but these early data are mostly derived from experiments using pharmacologic stimulation of gastric acid secretion in dogs and cats with surgically placed gastric fistulas.23 Although higher fasting gastric pH was reported in some studies,24 fasting gastric pH was comparable in dogs, cats, and humans in more recent studies.7, 8, 25, 26, 27 The intragastric pH of healthy control dogs measured with a catheter‐less pH capsule remained 85% of the time, with a mean percentage time (MPT) intragastric pH > 4.0 of only 4.7%.8 Similarly, in another study using the same methodology, the median gastric pH was 1.1 and the median percentage of the investigation time that the gastric pH fluctuated between 0.5 and 2.5 was 90.32% (range, 78%‐97.4%).7 In 2 recent studies recording intragastric pH in cats over 4 days using the same methodology, comparable results were reported.26, 27 These results compare well to the MPT intragastric pH > 4 of 4.4% reported for healthy people.28
Gastric pH in people increases with feeding because of the buffering effect of food, but dogs and cats differ because the buffering effect of food is not consistently observed and is much smaller in effect, if present at all.8, 24, 26 This observation may be caused by higher peak acid output in fed dogs. Another explanation may be differences in methodology, because the pH capsule methodology used in newer studies,7, 8, 26, 27 unlike digital probes, allows direct adherence to the gastric mucosa and provides direct measurement of intragastric pH.
Antacids are the oldest of the gastrointestinal (GI) protectants and comprise a group of inorganic, relatively insoluble salts of aluminum hydroxide (Al(OH)3), calcium carbonate (CaCO3), and magnesium hydroxide (Mg(OH)2) that lack systemic effects.29
Antacids also may be beneficial by decreasing pepsin activity, binding to bile acids in the stomach, and stimulating local prostaglandin (eg, PGE2) synthesis. There is an outdated belief that antacids are effective because they increase gastric pH, but this action is unlikely, or only temporary, because these agents do not exhibit strong enough buffering capacity.30, 31
Antacids are used only in humans with gastroesophageal reflux disease (GERD) clinical signs that occur infrequently, or as breakthrough agents in patients taking H2RAs or PPIs. One of the popular products used for reflux esophagitis in people is Gaviscon. The formulations in the United States contain aluminum hydroxide and magnesium trisilicate (tablet) or magnesium carbonate (oral suspension). The Gaviscon product available in the United Kingdom is more effective for reflux esophagitis than is the formulation sold in the United States. Whereas the US form of Gaviscon is primarily designed to neutralize acid, the formulation in the United Kingdom contains sodium alginate, with other antacid ingredients (Gaviscon Advance or Gaviscon Double Action Liquid). The addition of alginate is intended to form a physical barrier to prevent acid reflux into the esophagus32 or to neutralize the “acid pocket” that forms at the gastro‐esophageal junction.33 When alginate encounters gastric acid, it forms a foam that acts as a raft to float on top of stomach contents. This feature may act as a physical barrier in the cardia region to prevent acid reflux or to neutralize the acid pocket that forms on top of stomach contents after a meal.
The most common adverse effect of aluminum‐containing antacids is constipation, but adverse effects from antacids are rare because they are seldom administered long term. In renal failure, magnesium and aluminum accumulation may be a problem, and aluminum toxicity after administration of aluminum hydroxide has been documented in dogs with advanced renal failure.34 Antacids interfere with the PO absorption of other drugs (eg, tetracyclines, fluoroquinolones, and digoxin), if administered concurrently. The magnesium (Mg +2 ) and aluminum (Al +3 ) components, like any tri‐ or di‐valent cation can chelate fluoroquinolones or tetracyclines and inhibit PO absorption. If these drugs are used together, the antibiotic should be administered 2 hours before the antacid. Oral absorption of azole antifungal drugs can be decreased when gastric acidity is suppressed, and this effect is discussed in more detail later in this consensus statement.
Dosage recommendations for dogs and cats are based on anecdotal experience. The onset of action is rapid, and the effects last 30‐60 minutes, necessitating frequent administration.31 Empirical dosing of 5‐10 mL 6 times daily often is cited for dogs and cats, regardless of the animal's size or product used. The frequency of administration is an important disadvantage for administration to pets.
Although antacids may produce partial short‐term neutralization of gastric acid, insufficient evidence is available to recommend antacids for treatment of gastroduodenal ulceration and erosion (GUE) or GER disease in dogs and cats. These agents may be difficult to administer with the frequency needed to control gastric acid, and other longer acting and more effective acid‐suppressing agents are available.
Histamine type‐2 receptor antagonists (H2RAs; eg, cimetidine, ranitidine, and famotidine) inhibit acid secretion by competitively blocking H‐2 receptors on the parietal cell, thus decreasing basal and meal‐stimulated gastric acid secretion. The H2RAs are eliminated by a combination of renal excretion and hepatic metabolism. Continuous H2RA administration results in pharmacological tolerance.9, 35, 36 In dogs, such tachyphylaxis occurs within 13 days, and may be noticed within 3 days. The same phenomenon has been documented in cats. Daily famotidine administration resulted in a 60% decrease in MPT pH ≥ 3 in 16 healthy colony cats between days 1 and 13 of treatment.37 The phenomenon of tolerance appears to occur even more rapidly (12‐72 hours) in human subjects when the famotidine is administered IV.38 Tolerance may be caused by gastrin‐induced up‐regulation of enterochromaffin‐like cell (ECL) synthesis of histamine, which in turn competes with the antagonist at the parietal cell.39, 40 Because of this tolerance, abrupt discontinuation of H2RAs causes rebound acid hypersecretion in humans as a result of the trophic properties of gastrin on ECL cells.35
Measures of efficacy of H2RAs in companion animals are scarce. Notably, the degree of gastric acid suppression necessary for GUE prophylaxis or treatment in dogs and cats is undetermined. The H2RAs are inferior to PPIs for increasing intragastric pH, as well as for prevention of exercise‐induced gastritis in dogs.8, 26, 27, 41, 42, 43 In a study of beagle dogs, famotidine (0.5 mg/kg q12h) increased intragastric pH more and for a longer time compared to ranitidine (2 mg/kg q12h) based on continuous 24‐hour intragastric pH measurements via gastrostomy tube.41 Higher dosages of famotidine (1‐1.3 mg/kg q12h) had only a weak effect on intragastric pH in a study in healthy mixed‐breed dogs.8 Similarly, even though PO famotidine (1 mg/kg q24h) decreased the severity of gastric lesions in racing sled dogs compared with no treatment,43 omeprazole (0.85 mg/kg PO q24h) significantly decreased the severity and prevalence of gastric lesions compared with famotidine (1.7 mg/kg PO q12h) in a similar study.44 Similar findings were obtained in cats. Famotidine (0.88‐1.26 mg/kg PO q12h) was significantly more efficacious than placebo but inferior to omeprazole in increasing intragastric pH in healthy colony cats.26 In healthy cats, no difference was observed between ranitidine (1.5‐2.3 mg/kg PO q12h) and placebo.27
There is a lack of benefit for administration of H2RAs on a once‐daily basis in dogs and cats to treat GUE and reflux esophagitis. Monotherapy with an H2RA given twice daily is inferior to PPI treatment given twice daily in dogs and cats. There is no evidence of benefit of administration of an H2RA with a PPI for ulcer healing, and this combination may diminish the effectiveness of the PPI.
The PPIs (e.g. omeprazole, pantoprazole, esomeprazole, and lansoprazole) are substituted benzimidazole drugs that target the final common pathway of acid production. The PPIs are significantly more effective than H2RAs in increasing gastric pH and preventing and healing acid‐related tissue injury in people.45, 46 The PPIs are weak bases that are unprotonated at the physiologic pH of the blood. Once the PPI accumulates in the acidic environment of the active parietal cell, the drug becomes protonated and trapped where it forms disulfide bonds with cysteine residues on the alpha subunit of H + ‐K + ‐ATPases, producing enzyme inactivation.47, 48 Acid secretion resumes only after new proton pumps are synthesized, resulting in a prolonged effect after administration. Dormant parietal cells are activated after initial PPI administration. Thus, inhibition of acid secretion is approximately 30% of maximal on day 1 of administration because of incomplete binding to all H + ‐K + ‐ATPases. Maximal inhibitory effect is achieved within approximately 2‐4 days of PPI administration.48, 49, 50, 51 Because the inhibitory activity of PPIs is dependent on the ability to bind to active H + ‐K + ‐ATPase enzymes, plasma concentrations of PPIs do not necessarily predict their efficacy. The best surrogate predictors of the inhibitory effect of PPIs on gastric acid secretion are the area under the concentration‐time curve and gastric pH profile.52
Delay in maximal PPI activity also is related to their stability. When administered in an acid environment, the acid‐labile drug may be degraded before it reaches the intestine where it is absorbed systemically. After repeated administration, acid secretion gradually diminishes to maximize intestinal drug absorption.53 Initial treatment with IV formulations, administering an enteric‐coated delayed‐release formulation, or combining PO formulations with bicarbonate will decrease the lag‐time for achieving maximal effect. Breaking or crushing an enteric‐coated form, or using a compounded formulation may diminish this protective effect.54, 55 Because of shorter intestinal transit in dogs and cats, compared to humans, it is unknown if delayed‐release formulations are effective in small animals. Another hypothesis to explain increased concentrations with repeated doses is inhibition of cytochrome P450 enzymes by omeprazole, thus inhibiting its own metabolism.56 Omeprazole is a well‐known inhibitor of the predominant cytochrome P450 (CYP) enzyme in people, CYP 2C19. It is unknown which enzymes (if any) are inhibited in dogs or cats.
Acid secretion is activated by ingestion of a meal, and PPI effectiveness depends on the extent of activation of acid secretion at the time of drug administration. The PPIs are most effective when taken shortly before a meal (30‐45 minutes) or with a meal. Effectiveness in people is compromised if taken without a meal.57 In addition, effectiveness of omeprazole was markedly compromised in dogs if administered while acid secretion was inhibited by co‐administration of H2RAs.58 The R‐enantiomer of lansoprazole, dexlansoprazole, is a new slow‐release PPI, and gastric pH may not be impacted by timing of meal intake and administration of newer PPIs.59 It is unknown if these newer PPI formulations have an advantage for dogs and cats.
The PPIs are metabolized by cytochrome P450 enzymes. Omeprazole can inhibit its own metabolism or inhibit the metabolism of other drugs metabolized by the same enzyme.60, 61, 62 Drugs affected in people include warfarin, clopidogrel, and diazepam. The population of CYP enzymes is not the same in people and dogs.63, 64 Therefore, it is undetermined if omeprazole inhibits metabolism of these, or other drugs, in dogs.
The differences among the PPI drugs include, but are not limited to, the cysteine residue with which they form disulfide bonds, their pharmacokinetic properties (eg, half‐life, maximum concentration of the drug achieved in the plasma after dose administration [C max], time at which C max is attained [t max]), drug interactions, and susceptibility to CYP metabolism. These differences can translate into slight variation in acid suppression, but the magnitude of efficacy in people remains similar.65 Standard doses of esomeprazole, the S‐enantiomer of omeprazole, resulted in greater gastric acid control compared to standard doses of traditional PPIs.66, 67 The pharmacokinetics and acid suppressant efficacy of esomeprazole after IV, PO, and SQ administration in healthy beagles has been studied,68 but it was not compared to other PPIs.68 Intravenously administered esomeprazole was documented to significantly increase gastric and esophageal pH in dogs undergoing elective orthopedic procedures.69 However, with the exception of esomeprazole in the treatment of GERD, most clinical studies in people suggest that older generation PPIs (eg, omeprazole and pantoprazole) have similar efficacy for treatment of acid‐induced tissue injury.
There is no conclusive evidence in dogs and cats to show that one PPI is clinically more effective than another for the treatment of GUE in dogs or cats.
Clinical studies investigating the efficacy of PPIs in dogs and cats are limited. Most PPI studies in cats and dogs were designed as preclinical development trials for humans. Many of these studies involved pharmacologic stimulation of gastric acid secretion using healthy animals with surgically placed gastric fistulas. It is unknown if such results accurately reflect the clinical response of gastric pH to PPIs. In healthy dogs and cats, PPIs are consistently superior to H2RAs for increasing intragastric pH and prevention of exercise‐induced gastritis in dogs.8, 26, 27, 41, 44 With regard to frequency, omeprazole should be administered twice daily to approach pH goals in dogs and cats that were established for the treatment of acid‐related disorders in people.8, 27, 41, 70, 71 This conclusion is supported by a single report showing no benefit of once‐daily PO‐administered omeprazole compared to cimetidine or placebo in ulcer healing scores in dogs with aspirin‐induced ulcers.72 No benefit was detected in MPT intragastric pH ≥ 3 and 4 in healthy dogs when famotidine was administered concurrently with IV pantoprazole.73 Proton pump inhibitors should be gradually tapered after administration for ≥4 weeks to avoid rebound gastric acid hypersecretion (RAH).5 The dose can be decreased by 50% on a weekly basis, with cessation of evening dosing during the first week.
Based on evidence from studies in humans and research animals, PPIs administered twice daily are superior to other gastroprotectants for treating acid‐related GUE. Our consensus opinion is that PPIs should be tapered in dogs and cats after prolonged use of >3‐4 weeks.
Several documented and potential drug‐drug interactions have been associated with PPI administration. Administration of PPIs increases gastric lumen pH from a normal of 1‐2 units to ≥4 for a greater part of the day. Absorption of some drugs and nutrients requires acid because they exhibit pH‐dependent drug solubility or dissolution (ie, weak bases), others require an acidic pH for drug release from its protective coating. Therefore, simultaneous PPI administration with some drugs may affect PO absorption, decreasing systemic exposure and clinical effect.
Antifungal drugs of the azole class (eg, ketoconazole, itraconazole, voriconazole, and posaconazole) are inherently poorly soluble. They must undergo dissolution at a low pH for PO absorption and are ideally administered PO with food to stimulate acid secretion. Dietary lipids also help drug solubilization. Itraconazole solution for PO use is an exception because it is formulated in a cyclodextrin complex to maintain solubility in solution. Fluconazole also is an exception because it is more water soluble. Significant impairment of dissolution and PO absorption of ketoconazole has been shown experimentally when increasing the gastric pH profile in dogs.74 Similar results are expected from PO administration of itraconazole and posaconazole with acid‐suppressing agents.
Hydrochloric acid in the stomach promotes iron absorption because it reduces the ferric acid form to the more soluble ferrous form. Human patients on chronic PPI treatment may have decreased PO absorption of iron. The effect of chronic administration of PPIs on PO iron absorption has not been explored in small animals.
Mycophenolate is administered as mycophenolate mofetil, an ester prodrug that must be converted to mycophenolic acid to produce inhibition of purine synthesis and an immunosuppressive effect. Because intestinal disturbances are common among mycophenolate‐treated patients, PPIs often are prescribed to decrease GI problems.75 Mycophenolate mofetil requires acidic pH for dissolution of the medication and for hydrolysis to mycophenolic acid. If PPIs are administered concurrently, the increased pH decreases absorption of the active drug.75 This interaction has been identified in people, but has not been explored in dogs or cats.
The prodrug clopidogrel must be converted to the active form before inhibiting platelet function. In humans, the CYP enzymes are responsible for conversion to the active metabolite, but whether or not dogs and cats metabolize clopidogrel with the same enzymes is unknown. Because omeprazole inhibits the CYP2C19 enzyme in people, it potentially can interfere with the biotransformation responsible for the formation of the active metabolite of clopidogrel and compromise antiplatelet treatment.76 The US Food and Drug Administration (FDA) recommends that “concomitant use of drugs that inhibit CYP2C19 should be discouraged.” However, the importance of this interaction is controversial.76 Other factors contribute to variable effects of clopidogrel in people, including CYP2C19 enzyme polymorphism and variations in the enzyme paraoxanase‐1, which affects the biological activity of clopidogrel.77, 78 In a recent study, coadministration of omeprazole and clopidogrel to experimental dogs did not decrease the antiplatelet effects of clopidogrel, but the active metabolite was not measured.79
Although there is no direct evidence in dogs or cats, there is compelling evidence based on pharmacologic principles and reports from human medicine that PPIs should not be administered concurrently with other agents that require an acid milieu for oral absorption.79
Retrospective reports have linked PPIs to acute interstitial nephritis, acute kidney injury, and chronic kidney disease (CKD) in people,80, 81, 82 but these studies did not identify cause and effect and were limited by inability to control for bias and confounding variables. Other adverse effects associated with chronic PPI administration in people include dementia,83 cobalamin deficiency,84 osteoporosis and pathologic fractures,85 community‐acquired pneumonia,86 hypomagnesemia,87 cardiovascular events, Clostridium difficile‐associated diarrhea,88, 89 drug interactions, and spontaneous bacterial peritonitis in patients with hepatic cirrhosis.90 Virtually, all of these associations were published in observational cohort and retrospective studies, with similar limitations as highlighted above. Despite the long list of potential adverse effects associated with PPI treatment, the quality of evidence underlying these associations is consistently low. When treating dogs and cats, judicious use of PPIs and a critical evaluation of the risks versus benefits of PPI use are advised on a case‐by‐case basis. The implementation of standardized guidelines describing appropriate indications for PPI use may help limit the overuse of these agents.
Because these drugs are not FDA‐approved for dogs or cats, there is no mandatory reporting requirement and the incidence of adverse effects from PPIs is unknown in dogs and cats. Two potential adverse effects from chronic administration of PPI have received attention. Because of loss of negative feedback mechanisms, blood gastrin concentrations are increased as a result of PPI administration.91 Consequently, gastrin exerts a trophic effect on the gastric mucosa and has been linked to development of gastric tumors arising from ECL cells in rats. After years of experience with PPI use, this issue is no longer a concern in people. No similar studies have been done in dogs and cats.
Small intestinal bacterial overgrowth is another adverse consequence of chronic PPI administration in people.92, 93 Proton pump inhibitors increased survival of swallowed bacteria in the upper GI tract by decreased intestinal peristalsis, decreased gastric emptying, changes in epithelial mucus composition, increased pH, and increased bacterial translocation. Increased growth of bacteria in the upper GI tract may increase the risk of bacterial aspiration pneumonia.
Bacterial overgrowth can have deleterious consequences when PPIs are administered with other drugs that can injure the small intestinal (SI) mucosa.94 It is common to prescribe PPIs in patients at risk for upper GI injury from nonsteroidal anti‐inflammatory drugs (NSAIDs), but PPIs can alter the SI microbiome, increasing the risk of injury to the intestinal epithelium caused by NSAIDs. This effect is acid‐independent and unrelated to gastric mucosa injury caused by NSAIDs. Inhibition of intestinal cyclooxygenase 1 and 2 (COX‐1, COX‐2) enzymes injures the SI mucosa. Enterohepatic recycling of NSAIDs likely plays a role whereby high concentrations of NSAIDs in bile are secreted into the duodenum in close proximity to the major duodenal papilla. Some of the most serious intestinal lesions in dogs caused by NSAIDs occur in this region.10, 95, 96 Small intestinal injury may be caused by increased numbers of gram‐negative facultative anaerobic bacteria that flourish in the SI of patients treated with PPIs. Lesions are characterized by loss of villi, erosions, and multifocal ulcers distributed throughout the small bowel. Anemia also may occur. Whereas some bacteria play a protective role against intestinal mucosal injury by NSAIDs, the intestinal dysbiosis arising from PPI administration increases the risk of NSAID‐induced intestinal injury.94 Administration of antibiotics or probiotics may mitigate injuries caused by this drug combination,94 but such studies have not been conducted in dogs or cats.
Diarrhea is the most common adverse effect reported in association with PPI administration in dogs.41, 97 This adverse effect has not been reported in cats.26, 27 A pilot study performed in 6 healthy cats suggested that RAH may occur after abrupt PPI discontinuation after prolonged PPI administration and cause a mild transient change in the fecal microbiota.98
Evidence is lacking to show that administration of PPIs causes serious adverse effects in dogs or cats. However, intestinal dysbiosis is possible, which could lead to other complications, such as bacterial pneumonia or complications from NSAIDs.
Misoprostol is a synthetic prostaglandin E1 analogue that has relative specificity for parietal cell receptors and decreases histamine, pentagastrin, and meal‐stimulated gastric acid secretion.99 Misoprostol binds to prostaglandin receptors and inhibits histamine‐stimulated cAMP formation, but its cytoprotective effects occur at dosages below those necessary to inhibit gastric acid secretion. Cytoprotective effects are caused by increased bicarbonate secretion, decreased pepsin content of gastric secretion, preservation of tight junctions among epithelial cells, increased mucus layer, increased mucosal blood flow, and improvement of mucosal regenerative capacity.100 In dogs, absorption of PO misoprostol is nearly complete. Rate of absorption is slowed by food in the stomach, which may decrease adverse effects such as diarrhea.101
Results from 41 control dogs and 39 dogs treated with misoprostol and aspirin at dosages ranging from 25 to 35 mg/kg q8h have been published in refereed journals, (but only 1 was a randomized controlled trial [RCT]102, 103, 104, 105, 106; Table Table1). 1 ). Misoprostol dosages ranged from 3 μg/kg PO q12h to 15 μg/kg PO q8h. Dosing misoprostol once daily appears inadequate compared to administration q8h to q12h.104 Misoprostol significantly decreased GUE or hemorrhage associated with aspirin, but it did not completely eliminate gastric lesions. Misoprostol can be considered as prophylaxis for NSAID treatment if there is clearly a need for prophylaxis and PPIs fail or cannot be used. Except for aspirin, effectiveness of misoprostol for GI injury from other NSAIDs has not been tested in dogs and cats. Misoprostol is less effective for treating or preventing duodenal ulcer (DU) compared to GUE in both dogs and cats.107, 108
Published studies on the effect of misoprostol on dogs and cats treated with nonsteroidal anti‐inflammatory drugs (NSAIDs), corticosteroids, or Escherichia coli
| Author | Species | Type of study (n) = number of animals in group | Dose of MIS | Aggressor agent and dose | Effects |
|---|---|---|---|---|---|
| Arvidsson1 | Cat | Experimental | 5 μg/kg/h IV | Live E. coli IV | |
| Arvidsson2 | The relationship between this abstract and the experimental study listed above is uncertain. Hence, the data are not listed. | ||||
| Holroyde3 | Dog | Experimental | 1, 5, and 10 μg/kg PO given before each dose of ACA | ACA (65 mg/kg 4X in 24 hours) | MIS reduced gastric mucosa injury as determined endoscopically |
| Johnson4 | Dog | Experimental ACA alone (6), MIS alone (6), ACA + MIS (6) | 3 μg/kg PO q8h | ACA (35 mg/kg q8h) | MIS reduced gastric mucosal injury as determined endoscopically |
| Bowersox5 | Dog | Experimental No treatment (5), ACA alone (5), MIS alone (5), ACA + MIS (5) | 15 μg/kg PO q8h for 5 days, then 7.5 μg/kg q8h | ACA (35 mg/kg q8h) | MIS eliminated all gastric mucosal injury as determined endoscopically except 1 dog that had 1 petechia |
| Ward6 | Dog | Experimental ACA alone (6), ACA + MIS at q8 (6) or q12 (6) or q24h (6) | 3 μg/kg PO at either q8h, q12h or q24h | ACA (25 mg/kg q8h) | MIS administered q8h and q12h reduced gastric mucosal injury as determined endoscopically |
| Guannoukas7 | Dog | Experimental VAG alone (10), DIC alone (10), VAG + DIC (10), DIC + MIS (10), VAG + DIC + MIS (10) | 8‐20 μg/kg PO q6h | DIC (1 mg/kg IM q24h for 12 days) mucosal injury | MIS alone did not prevent mucosal injury as determined by necropsy; MIS plus VAG reduced gastric |
| Rohrer8 | Dog | Placebo controlled trial Surgery + steroid (9), Surgery + steroid + MIS (9) | 4‐6 μg/kg PO q8h | Methylprednisolone 30 mg/kg IV, then 15 mg/kg q6h | MIS did not reduce gastric hemorrhage as determined endoscopically |
| Dogra9 | Dog | Experimental All dogs received steroid until ulcer formation, then lansoprazole (4), sucralfate (4), famotidine (4), MIS (4), herbal (4) | 10 μg/kg PO (frequency uncertain) | Dexamethasone 1 mg/kg q12h until have ulcer | MIS administration associated with slowest rate of healing of previously formed steroid‐associated ulcers |
| Murtaugh10 | Dog | Randomized, double‐blind trial ACA only (8), ACA + MIS (10) | 100 μg/dog PO q8h = 3.1 μg/kg (mean), range 2.3‐5 μg/kg | ACA (25 mg/kg q8h) | MIS reduced gastric mucosal injury as determined endoscopically |
| Hansen11 | Dog | Randomized clinical trial All dogs had spinal surgery + steroids: control (10), cimetidine (10), sucralfate (10), MIS (10) | 4 μg/kg PO q8h | Methylprednisolone 30 mg/kg IV, ± 2nd dose 15‐30 mg/kg IV | MIS did not reduced GI blood loss as determined by gross examination or stool guiac slide test |
| Neiger12 | Dog | Randomized clinical trial All dogs had spinal surgery + dexamethasone: control (8), MIS (8), omeprazole (9) | 2 μg/kg PO q8h | Dexamethasone 2 mg/kg IV followed by 1 mg/kg and then 0.5 mg/kg | MIS did not reduce gastric mucosal injury as determined endoscopically |
| Satoh13 | Cat | Experimental ACA only (4‐6), ACA + MIS (4‐6), ACA + cimetidine (4‐6) | 3 μg/kg PO q12h | ACA (20 mg/cat) | MIS reduced gastric mucosal injury as determined by necropsy examination |
Abbreviations: ACA, aspirin; DIC, diclofenac; IV, intravenous; MIS, misoprostol; PO, per os; VAG, highly selective vagotomy.
No evidence supports the use of misoprostol for preventing corticosteroid‐induced GUE in dogs.109, 110 Misoprostol administration to laboratory dogs at 4‐6 μg/kg q8h did not prevent endoscopically visible gastric hemorrhage associated with methylprednisolone administration (30 mg/kg initially and then 15 mg/kg for an additional 6 doses over 48 hours).110 The RCTs assessing the efficacy of misoprostol in dogs with intervertebral disc disease treated with surgery and high‐dose corticosteroids did not show a benefit from misoprostol or other gastroprotectant drugs.109, 111
Two published studies have evaluated the efficacy of misoprostol in cats. A constant rate infusion of misoprostol to laboratory cats in which septic shock was induced was found to be superior to administration of superoxide dismutase in decreasing GUE.112 Misoprostol administered at 3 μg/kg q12h also was shown to decrease aspirin‐associated GUE (but not duodenal ulceration) in a study comparing the efficacy of misoprostol and cimetidine.108
Adverse effects, in particular abdominal pain and diarrhea, are the main reasons why misoprostol is used infrequently in people to prevent GUE.113 Abortion (because of increased tonus of the uterus and cervical softening) is an important adverse effect of the drug and has become the primary reason for misoprostol administration as an abortifacient in people.114
Misoprostol is effective for decreasing gastric lesions in dogs treated with high‐dose aspirin, but it is unknown if misoprostol is effective for preventing GUE associated with administration of other NSAIDs in dogs and cats. There is no evidence that misoprostol decreases GUE from glucocorticoids in dogs and cats.
Sucralfate (Carafate) is a complex salt of sucrose octasulfate and aluminum hydroxide.115 Its mechanism of action in acid‐peptic disease is multifactorial. Sucralfate forms stable complexes with protein in damaged mucosa where there is a high concentration of protein, either from fibrinogen, albumin, or globulins from the exudate of an ulcer or from damaged cells.115
In an acidic environment, sucralfate becomes viscous and partially dissociates into sucrose sulfate and aluminum hydroxide. The sucrose sulfate moiety is an anion and binds electrostatically with the positively charged proteins in the damaged mucosa.115 Sucralfate interferes with the action of pepsin either by preventing pepsin digestion of protein substrates, by binding to pepsin, or by providing a barrier to prevent diffusion of pepsin.115 In addition, the protection afforded by sucralfate against esophageal acid injury is mediated by intraluminal pH buffering via aluminum hydroxide and protection against H + entry and injury via sucrose octasulfate.116
In an ex vivo model of acid‐induced mucosal bleeding in dogs, sucralfate was effective in promoting repair of the gastric mucosal tissue when applied at the time of or shortly after acid‐induced injury.117 Sucralfate also may provide a barrier for bile salts. Sucralfate is known to stimulate prostaglandin production in the gastric epithelium. This may be a potential secondary effect of sucralfate in the esophagus, although the importance and effectiveness of sucralfate as an agent for the treatment of erosive esophagitis is not as established as it has been for H2RAs or PPIs.
In rabbits, esophagitis induced by acid and pepsin was prevented by administration of sucralfate.118 In another study, cats pretreated with liquid sucralfate before acid infusion were protected against esophagitis.119 Studies in humans have compared sucralfate to other forms of treatment including alginic acid/antacid, cimetidine, and ranitidine. Sucralfate was as effective as Gaviscon containing sodium alginate with regard to healing of esophagitis and symptomatic improvement.120, 121 The H2RAs, ranitidine and cimetidine, and sucralfate had equal efficacy for treating reflux esophagitis,121, 122, 123, 124, 125 although higher grade esophagitis did not heal as well compared to lower grade esophagitis. In foals, sucralfate had a protective effect on oral, esophageal, and gastric ulcers associated with IV administration of high‐dose phenylbutazone.126 When sucralfate is compared to placebo, conflicting data regarding therapeutic benefit have been obtained in human patients with reflux esophagitis.127 Limited esophageal retention time may decrease effectiveness. In a study of technetium‐labeled sucralfate, the drug was retained within the esophagus for 3 hours in 2RA, compared to either drug alone in treating acute duodenal ulcer, in ulcer maintenance treatment, in stress bleeding, or in reflux esophagitis.
Sucralfate is a relatively safe compound and has minimal adverse effects. Aluminum absorption during sucralfate treatment is comparable to that during treatment with aluminum hydroxide, and caution should be exercised with long‐term treatment in patients with renal insufficiency to avoid aluminum intoxication.132, 133 Constipation, caused by aluminum hydroxide, is one of the most common adverse effects, and typically occurs in 1%‐3% of human patients taking the drug.134 Other adverse effects in humans include xerostomia, nausea, vomiting, headache, urticaria, and rashes in 0‐5% of patients.134, 135
Coadministration of the following drugs with sucralfate results in a substantially decreased bioavailability of single doses of the drug: ciprofloxacin,136, 137, 138 theophylline,139 tetracycline, doxycycline, minocycline,140, 141 phenytoin,142 and digoxin.143 The bioavailability of digoxin, tetracycline, doxycycline, and phenytoin was not decreased when they were given 2 hours before sucralfate. Sucralfate impairs absorption of ciprofloxacin in humans and dogs when administered concurrently,136, 144 but the bioavailability of ciprofloxacin is markedly increased when administration of sucralfate is delayed by 2 hours. Interestingly, no significant difference in bioavailability was documented for enrofloxacin coadministered with sucralfate in dogs.136, 144
In contrast to sucralfate suspension, administration of sucralfate tablets had no effect on the absorption of doxycycline in dogs.140 This lack of interaction with sucralfate tablets suggests sucralfate tablets do not adequately disintegrate in dogs and should be administered as a suspension rather than an intact tablet.
There is weak evidence in experimental animals and humans to support the use of sucralfate for preventing or treating esophageal injury. There is moderate evidence that sucralfate may have analgesic effects in people post‐tonsillectomy, but no studies have evaluated the analgesic properties of sucralfate in people or animals with esophagitis. No evidence supports either a benefit or interaction when sucralfate is administered concurrently with H2RAs or PPIs. When administered to dogs (and perhaps cats), intact tablets may not fully disintegrate and may not be as effective as a liquid suspension. No evidence indicates that combining sucralfate with either a PPI or an H2RA for treatment of GUE is beneficial or indicated. Proton pump inhibitors are superior to sucralfate for management of GUE.
In a meta‐analysis involving >14 000 patients, healing of gastric and duodenal ulcers and erosive esophagitis were directly related to the extent and duration of gastric acid suppression over a 24‐hour period.70, 71 Healing of esophagitis was significantly correlated with maintaining gastric pH ≥ 4.0 for at least 16 hours per day, whereas treatment of duodenal ulcers was optimized by maintaining gastric pH ≥ 3 for 18‐20 hours per day.71 Control of nocturnal acidity (as opposed to 24‐hour acidity) was directly proportional to healing of duodenal ulcers.145 In a meta‐analysis involving 56 published clinical trials in people, healing of benign gastric ulcers was most strongly correlated with the duration of treatment, unlike with duodenal ulcers.146
The FDA has listed indications for the use of PPIs in adult human patients (Table (Table2), 2 ), and treatment of Helicobacter pylori peptic ulcers147 and GERD148 are universally considered indications for PPIs. Treatment of erosive esophagitis,149 benign gastric ulcers,150 dyspepsia,151 hypersecretory states (eg, Zollinger‐Ellison syndrome),152 and prophylaxis for NSAID‐associated ulcers153 also are listed as indications for PPI treatment.
The Food and Drug Administration (FDA) indications for the use of proton pump inhibitors in people compared to lists of questionable indications found in other publications
| Diseases | US FDA a | Kelly et al.224 | Rotman et al.225 | Reid et al.226 |
|---|---|---|---|---|
| Duodenal ulcer (ie, peptic ulcer) | X | X | X | X |
| Treatment of Helicobacter pylori | X | X | X | X |
| Esophagitis | X | X | X | |
| GERD | X | X | X | X |
| Gastric ulcers | X | X | X | |
| Drug prophylaxis for NSAID | X | X | X | |
| Hypersecretory (Zollinger‐Ellison) | X | X | ||
| “Heartburn” | X | X | ||
| Functional dyspepsia | X | X | X | |
| Gastritis | X | X | ||
| Barrett's esophagus | X | |||
| Esophageal varices | X | X | ||
| Malignant neoplasm of stomach/esophagus | X | |||
| Hepatic disease | X | |||
| Abdominal pain | X | |||
| Chest pain | X | |||
| Cough | X | |||
| Drug prophylaxis for steroids or antiplatelet drugs | X | |||
| Esophageal perforation | X | |||
| Duodenitis | X | |||
| Gastroparesis | X | |||
| Unspecified hemorrhage of GIT | X | X |
Gastrointestinal and pancreatic neoplasia, NSAIDs, hepatic disease, and inflammatory bowel disease were reported in 2 retrospective studies to be associated with GUE in dogs.95, 154 Non‐neoplastic causes of GUE including NSAID‐induced injury are associated with ulceration of the gastric fundus, body, pylorus, antrum, and duodenum.154 In cats, overt GI bleeding secondary to ulcerative disease is not as common as in dogs,155 but GI and pancreatic neoplasia are common causes of GUE in cats.156 Gastrointestinal ulceration in cats induced by NSAIDs is uncommon. Duodenal ulceration tends to be more common in cats with extraintestinal neoplasia such as gastrinoma. It is challenging to identify the causes of non‐neoplastic GUE in cats.156 The efficacy of gastroprotectants in cats for the treatment of GUE secondary to these conditions is underexplored and limited to a few reports.95, 154, 155, 156 Regardless of the cause of GUE in dogs and cats, suppression of acid secretion should improve healing. If PPIs are used, twice‐daily administration is superior to once‐daily administration to achieve goals of acid suppression for treatment of GUE.
Proton pump inhibitors are superior to H2RAs, sucralfate, and misoprostol for most causes of GUE in people, and should be considered as standard of care for the medical treatment of GUE in dogs and cats.
In small animal medicine, gastric acid suppressants often are administered in suspected and histologically confirmed cases of gastritis. The benefit of this regimen is largely extrapolated from human medicine where gastric acid suppression is used to treat H. pylori gastritis, a distinct infection not recognized in dogs and cats. The benefit of gastric acid suppression in cases of idiopathic gastritis is not explored. Vomiting may be the primary sign of gastritis in dogs and cats, but acid‐suppressant drugs should not be used as antiemetics. Acid suppression with famotidine (0.5 mg/kg q24h) did not affect treatment efficacy or frequency of clinical signs in 23 dogs with histologic evidence of gastritis and spiral bacteria in gastric mucosal biopsy samples.157 Helicobacter‐negative gastritis can occur in people and may be comparable to idiopathic gastritis in cats and dogs, but no therapeutic regimens have been reported effective for this condition.158
There is no evidence to support the prophylactic use of gastroprotectant therapy in dogs and cats with nonerosive gastritis.
Although hepatic disease has been associated with GUE in dogs, evidence that it is a direct cause of GUE is scarce,154, 159 and the prevalence of upper GI bleeding has not been assessed in dogs and cats with hepatic disease. The pathogenesis of GUE associated with hepatic disorders is uncertain. Altered mucosal blood flow because of portal hypertension (ie, hypertensive gastropathy) is the most common cause for GI bleeding in humans.160 Decreased hepatic degradation of gastrin and subsequent stimulation of acid hypersecretion may occur in dogs.161 In a study of dogs with experimentally induced hepatic disease however, low serum gastrin concentrations refuted hypergastrinemia as a cause of GUE in dogs with hepatic disease (Boothe DM. Serum gastrin levels in dogs with progressive liver disease. J Vet Intern Med. 1990;4:122). No difference was found in serum gastrin concentrations between dogs with hepatic disease and healthy controls,162 but continuous intragastric pH monitoring and GI endoscopy were not performed. Experimental bile duct ligation also can produce gastric ulceration.161 In humans, gastric acid suppression generally is not considered effective at decreasing bleeding associated with portal hypertensive gastropathy, because these patients already have hypochlorhydria.160 However, PPIs indirectly may stop gastric bleeding by increasing intraluminal gastric pH and thereby stabilizing blood clots.163 An auxiliary finding in a recent study on endovascular treatment of intrahepatic shunts in dogs was a substantial decrease in deaths attributed to GI hemorrhage or ulceration after implementation of peri‐ and postsurgical lifelong administration of PPIs.164 However, the mechanism for GI bleeding in these dogs is uncertain and may not be related to hepatic dysfunction or portal hypertension.
There is weak evidence to support the prophylactic use of acid suppressant therapy in dogs and cats with hepatic disease that is not associated with GI bleeding.
The benefits of stress ulcer prevention in intensive care unit (ICU) patients currently are unresolved. Administration of H2RAs to people receiving enteral nutrition was associated with an increased risk of hospital acquired pneumonia and mortality.165 In a meta‐analysis of 14 randomized, controlled parallel group trials involving 1720 people in an ICU, PPIs were more effective than H2RAs in preventing clinically important upper GI bleeding, but their use did not decrease mortality in the hospital or the duration of ICU stay.166
Stress‐related mucosal damage occurs in some critically ill dogs and cats, but its prevalence, severity, and the efficacy of prophylactic gastroprotection is unknown.167 In a retrospective study evaluating SRMD in critically ill dogs from 3 ICUs in the United Kingdom, hemorrhagic gastric disease was significantly associated with mortality. However, gastroprotectant drugs did not improve survival in this population of dogs.168
Although no evidence supports the routine use of H2RAs or PPIs for prevention of SRMD in critically ill dogs and cats, they may prevent GUE in performance animals. Most of the research on SRMD in dogs has been performed on racing Alaskan sled dogs. Strenuous exercise in increments of 100 miles/d for 5 days was associated with development of SRMD.169 Gastric erosions, ulcers, and hemorrhage were observed in 48% of 70 dogs after completing the Iditarod sled dog race.97 The study was limited by not examining the dogs before and after the race, precluding confirmation of when the lesions might have been present. Omeprazole (0.85 mg/kg PO q24h) was significantly superior to high‐dose famotidine (1.7 mg/kg q12h) in decreasing SRMD in a randomized positive control study of 52 dogs before and after a 300‐mile race.44 Stress‐related mucosal disease also has been documented in Labrador retrievers undergoing explosive detection training in North Carolina during the summer months.170 In an experimental study on 20 horses, gastric ulceration was associated with decreases in physiologic indices of performance.171 Therefore, in highly competitive events (eg, sled dog racing) or working dogs in adverse environments (eg, military working dogs), there may be benefits to PPI administration.
There is no compelling evidence that gastroprotectant therapy is beneficial or indicated in critically ill human and animal patients unless definite risk factors such as GI hemorrhage or concurrent NSAID administration are present. Prophylactic PPI administration to animals competing in strenuous, competitive events might decrease SRMD and improve overall performance.
Gastric acid secretion is variably affected by renal dysfunction in humans and may partially depend on H. pylori infection status.172 However, gastritis and GUE can be complications of end‐stage renal disease in human patients.173, 174 Acid suppression in people is often recommended for renal disease patients with ulcer bleeding.175 There is no recommendation for the use of prophylactic acid suppressant treatment in human patients with renal disease, but acid suppressants generally are recommended if other risk factors (eg, NSAID or corticosteroid treatment) for ulcer development are present. Dose adjustments of H2RAs based on projected glomerular filtration rate are recommended because of the renal elimination of these drugs.176
Gastroduodenal ulceration and erosion is not a typical finding in dogs and cats with advanced renal disease.177, 178, 179, 180 Moreover, in a recent study of 10 cats with chronic renal disease and 9 healthy age‐matched control cats, no significant differences were observed in serum gastrin concentrations and gastric pH between groups, suggesting that cats with CKD may not have gastric hyperacidity compared to healthy cats, and therefore, may not need acid suppression.181 However, despite this evidence, acid suppressants are commonly prescribed to dogs and cats with CKD.182 Chronic administration of acid suppressants to dogs and cats with CKD may not be benign. Prolonged administration of acid suppressants has been associated with derangements in serum calcium and PTH concentrations, osteoporosis, and pathologic fractures in at‐risk human populations.183
Approximately 36%‐80% of cats with moderate to severe CKD have renal secondary hyperparathyroidism,184, 185 with possible consequences of decreased bone mineral density and increased bone resorption cavities.186 Thus, the deleterious effects of chronic acid suppressant administration on calcium metabolism and bone remodeling in dogs and cats with CKD could lead to serious sequelae. Positive fecal occult blood tests have been documented in dogs with CKD,187 but the mechanism of GI bleeding and benefit of acid suppressant treatment have not been investigated. Until such studies are published, acid suppression should be restricted to dogs and cats with renal disease that have additional risk factors for ulceration or when concern for severe GI bleeding (eg, melena, severe iron deficiency anemia) or vomiting‐induced esophagitis exists.
There is no evidence to support the prophylactic use of gastroprotectants in dogs and cats with International Renal Interest Society (IRIS) stages 1‐3 renal disease. Additional studies are warranted to determine the benefits of acid suppression in animals with IRIS stage 4 renal disease.
Gastric acid suppressants frequently are used in the management of acute pancreatitis in dogs and cats. The rationale for acid suppression is the perceived increased risk of upper GI bleeding with pancreatitis secondary to hypovolemia and local peritonitis, but the incidence of upper GI bleeding in dogs and cats with pancreatitis currently is unknown. Similarly, severe illness, hypoxemia, and use of NSAIDs for pain relief, together with GI hypoperfusion, have been proposed as potential causes of GI mucosal barrier failure, and contribute to acute mucosal lesions or ulcers in people with severe acute pancreatitis.188 In some reports, PPIs are anti‐inflammatory and decrease pancreatic secretions, whereas in others there is no effect or a pro‐inflammatory effect.189, 190, 191 Pantoprazole possesses reactivity toward hydroxyl radicals and ameliorates inflammation in rodent models of pancreatitis,191 but a recent placebo‐controlled study failed to demonstrate a benefit of pantoprazole administration in human patients with acute pancreatitis.192
There is no evidence that acid suppression treatment is beneficial or indicated in the management of dogs or cats with pancreatitis, unless the animal has concurrent evidence of GUE.
Gastroesophageal reflux during anesthesia is associated with 46%‐65% of cases of benign esophageal stricture in dogs and represents the most common cause of high‐grade esophagitis and stricture formation in dogs.193, 194 Relaxation of the lower esophageal sphincter (LES) is mediated by nonadrenergic noncholinergic pathways195 and has been shown to occur with the administration of injectable preanesthetic and inhalant anesthetic agents.196, 197, 198 The LES may be rendered incompetent by a sliding hiatal hernia, which often is accompanied by GER and can be exacerbated by increased inspiratory effort typical of brachycephalic breeds.199
The superiority of PPIs in healing erosive esophagitis and decreasing rate of relapse compared to that of H2RAs has been well established in people.46, 206, 207 In addition, treatment with PPIs provided quicker and more complete relief from heartburn clinical signs (11.5% per week) compared with H2RAs (6.4% per week). Proton pump inhibitors were found to provide greater clinical sign relief in patients with erosive reflux disease (70%‐80%) as compared to those with nonerosive reflux disease (50%‐60%).208 Additional studies are warranted to determine the benefits of preanesthetic administration of H2RAs in dogs and cats in which prolonged maintenance of esophageal pH > 4.0 is not necessary.
There is a lack of empirical evidence in dogs and cats, but compelling evidence from studies in people, that acid‐suppressing agents may be beneficial for prevention of esophagitis secondary to GER, particularly in animals when it is associated with an anesthetic procedure. Administration of PPIs does not decrease gastric reflux, but may prevent injury by increasing the pH of the refluxate.
Treatment of H. pylori in people currently consists of multiple drugs, either simultaneously or sequentially, and PPIs are almost always an integral component of treatment.209, 210 Infected dogs and cats almost always have non‐H. pylori Helicobacter (NHPH) that appears to have different pathophysiologic effects and different responses to treatment compared to H. pylori. The importance of triple or quadruple treatment for effective management of H. pylori in people might not translate to the same recommendation for dogs and cats with NHPH. Ten studies report treatment of spontaneous NHPH in dogs and cats (Table (Table3). 3 ). The variety of therapies employed, the relatively small number of animals studied, and the different means and times by which elimination of Helicobacter were determined make it impossible to draw meaningful conclusions about the value of acid suppression treatment when treating dogs or cats with NHPH. A single RCT compared antibiotics with and without acid suppression and showed no benefit from adding famotidine, but the study was relatively underpowered.157 Because PPIs are superior to H2RAs in decreasing gastric acidity, a similar study with PPIs might have different results. However, based upon currently available information, acid suppression treatment with H2RAs is not indicated for first‐line treatment when treating NHPH in dogs or cats.
Results of treatment of Helicobacter spp. in dogs and cats
| Author | Species | Type of study/design (n) = # animals/group | Antibacterials used (days) | Acid suppression used | Results | Means of evaluating efficacy (time of testing post treatment) |
|---|---|---|---|---|---|---|
| Kubota1 | Dogs | Uncontrolled experiment | AMO, MET (14) | OME | 6/6 cleared | HIST, RUT, PCR (uncertain) |
| All dogs treated (6) | ||||||
| Simpson2 | Dogs | Controlled experiment | AMO, MET (14) | FAM | 6/8 cleared at 4 days | HIST, RUT, IMP (4 days) |
| Treated (8), untreated (6) | 0/8 cleared at 29 days | HIST, RUT, IMP (29 days) | ||||
| Mirzaeian3 | Dogs | Uncontrolled experiment | AMO, CLA (7) | LAN | 20/20 cleared | HIST, RUT (uncertain) |
| All dogs treated (20) | ||||||
| Costa4 | Dogs | Controlled experiment | AMO, MET (15) | OME | 7/7 cleared | HIST (uncertain) |
| No tx (7), antibiotics (7) garlic oil (7) | ||||||
| Happonen5 | Dogs | Uncontrolled clinical trial (9) | AMO, MET (10‐14) + BIS | None | 7/9 cleared | HIST (within 84 days) |
| Repeated tx for initial failures | TET (10) | OME | 1/1 cleared | HIST (within 84 days) | ||
| Jergens6 | Dogs | Uncontrolled clinical trial (3) | AMO, MET, BIS (21) | None | 3/3 cleared | HIST, FISH, PCR (4‐14 weeks) |
| Cats | Uncontrolled clinical trial (2) | AMO, MET, BIS (21) | None | 2/2 cleared | HIST, FISH, PCR (4‐14 weeks) | |
| Leib7 | Dogs | Randomized clinical trial | AMO, MET, BIS (14) | |||
| Tx with antibiotics (10) | None | 7/10 cleared | HIST (4 weeks) | |||
| Tx with antibiotics + famotidine (14) | FAM | 11/14 cleared | HIST (4 weeks) | |||
| Khoshnegah8 | Cats | Uncontrolled experiment | AMO, MET, CLA (14) | OME | 13/13 cleared | HIST (uncertain) |
| All cats treated (13) | ||||||
| Perkins9 | Cats | Controlled experiment | AMO, MET (21) | OME | 6/6 cleared | CUL of mucosa/fluid (2 weeks) |
| Treated (6), untreated (2) | 1/6 cleared | PCR (2 weeks) | ||||
| Neiger10 | Cats | Controlled clinical trial | ||||
| Untreated (4), Antibiotics‐1 (6) | AZI, BIS, TIN (4) | 4/6 cleared | Urea breath test (10 days) | |||
| Antibiotics‐2 (11) | CLA, MET, BIS (4) | RAN | 11/11 cleared | |||
| Antibiotics‐3 (8) | CLA, MET, BIS (7) | RAN | 8/8 cleared |
Abbreviations: AMO, amoxicillin; AZI, azithromycin; BIS, bismuth subcitrate or subsalicylate; CLA, clarithromycin; CUL, culture; FAM, famotidine; FISH, fluorescent in situ hybridization; HIST, histology of gastric mucosa; IMP, impression smears of gastric mucosa; LAN, lansoprazole; MET, metronidazole; OME, omeprazole; PCR, polymerase chain reaction testing; RAN, ranitidine; RUT, rapid urea testing of gastric mucosa; TET, tetracycline; TIN, tinidazole.
There is no evidence that acid suppression treatment is beneficial or indicated in dogs or cats undergoing treatment for NHPH.
In experimental studies, platelet aggregation at an ulcer is essentially normal at a gastric pH 7.4, but progressively diminishes until absent at pH ≤ 6.2.211 Increasing gastric pH may limit degradation of previously formed platelet plugs and decrease proteolytic activity of pepsin on existing thrombi. Proton pump inhibitors in combination with other therapies have been successful for treatment of gastric bleeding in human patients with myelodysplasia and thrombocytopenia or idiopathic thrombocytopenia purpura.212, 213 Despite this phenomenon, acid suppressants are not routinely administered in humans with immune‐mediated thrombocytopenia (ITP). Gastrointestinal hemorrhage is rarely observed in human patients with ITP.214 In contrast, GI bleeding is relatively common in dogs with ITP.215 Platelet aggregation and clot formation in vitro are optimal at pH > 6.8.216, 217 For this reason, acid suppressants are commonly used as adjunctive treatment of dogs with ITP‐related GI bleeding. However, in a recent study, acid suppressants did not influence the probability of survival to discharge.176 In studies of healthy dogs and cats, twice‐daily administration of acid suppressants did not achieve the target of pH > 6 for a prolonged period.178, 179, 180, 182 More studies are warranted to determine the efficacy and optimal dosage of acid suppressants for the treatment of thrombocytopenic‐induced GI bleeding in dogs and cats.
There is insufficient evidence to support the use of standard dosages of acid suppressant treatment for prevention or management of thrombocytopenia‐induced bleeding.
Spinal cord injury and intervertebral disc surgery in dogs have been associated with GI complications in dogs. Information for cats is not available to make any conclusions.
A consistent finding in the published reports of GI complications in dogs with spinal cord disease and spinal surgery is that high doses of corticosteroids were administered (eg, 30 mg/kg methylprednisolone, which is equivalent to 3.75 mg/kg dexamethasone). In these reports, there were high rates of GI complications, including diarrhea, melena, bleeding, and perforation.111, 218, 219, 220, 221 The same findings have been reported in research dogs that had spinal surgery in combination with high‐dose corticosteroids.222
These reports concluded that the high doses of corticosteroids contributed to GI complications rather than disc disease or surgery alone. High doses of corticosteroids administered to otherwise healthy dogs can produce gastric hemorrhage.223 Injury from glucocorticoids is not caused by hypersecretion of acid, but is more likely the result of decreased defense mechanisms and altered gastric mucosal blood flow. Sympathetic‐parasympathetic imbalance in spinal surgery patients may contribute to the GI problems.109
No evidence from clinical reports of dogs or from research studies shows that gastroprotectant drugs are beneficial for preventing or decreasing GI complications from high doses of corticosteroids. The gastroprotectants used in these reports were sucralfate, misoprostol, and H2RAs. We acknowledge that some of these reports were from the 1980s, before the use of PPIs, although a more recent study showed no benefit in healing or preventing development of gastric mucosal lesions in dogs using either misoprostol or omeprazole.109
Gastrointestinal complications associated with spinal cord disease and spinal surgery are more likely caused by the administration of high doses of glucocorticoids than other factors. In these cases, there is no convincing evidence that gastroprotectant drugs are beneficial.
This consensus statement has highlighted the problems our panel faced when attempting to provide recommendations for or against the use of gastric protectants in dogs and cats. There is a need for the use of selected GI protectants in some patients, but there is ample evidence documenting overuse of these drugs for many disorders in dogs and cats. Veterinarians need to better define the appropriate clinical applications for the use of gastroprotectants in small animals. Technological advances have become available with the use of GI telemetric monitoring devices and capsule endoscopy that should facilitate future research to more precisely identify the efficacy of these drugs in dogs and cats. Well‐defined endpoints and goals of treatment should be established. The benefits of gastroprotectants that we have defined in this article are largely based on extrapolation from human medicine or from studies in healthy dogs and cats. More information is needed to define optimal dosage, timing of doses, and selection of products (eg, one PPI versus another), particularly in clinical patients. Newer generation PPIs, such as delayed‐release and longer‐acting PPIs, are commercially available and may improve dosing and effectiveness in dogs and cats. We are cognizant that not a single agent listed in this article is FDA‐approved for use in dogs or cats. Clearly, the pharmaceutical industry should become involved in evaluating these drugs. Controlled studies evaluating the efficacy of gastroprotectant drugs in clinical patients, as well as the judicious application of these drugs, should further optimize the management of reflux esophagitis and GUE in dogs and cats.
Stanley L. Marks has consulted for Zoetis (Formerly Pfizer Animal Health), Aratana Therapeutics, and Virbac; received research funding from Aratana Therapeutics, Morris Animal Foundation, Winn Feline Foundation; received speaking honoraria from Zoetis (Formerly Pfizer Animal Health), Aratana Therapeutics, Virbac, Elanco, Nutramax Laboratories. Michael D. Willard serves as Associate Editor for the Journal of Veterinary Internal Medicine. He was not involved in review of this manuscript. Mark G. Papich has consulted for Zoetis (Formerly Pfizer Animal Health), Bayer Corporation, Dechra (formerly Putney), Merck Animal Health, Elanco, Novartis, Pennfield (now Pharmgate), e5pharma, and Kindred Biomed; authored veterinary drug books published by Elsevier and Wiley; received research funding from Bayer Corporation, Merck Animal Health, Zoetis (Formerly Pfizer Animal Health), and Morris Animal Foundation; received speaking honoraria from Zoetis (Formerly Pfizer Animal Health), Dechra (formerly Putney), and Bayer Corporation. M. Katie Tolbert received research grants from the Comparative Gastroenterology Society, Morris Animal Foundation, Winn Feline Foundation, and The ACVIM Foundation to study acid suppressants in cats.
Appendix S1 Supporting information