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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice symPTomaTic maNagemeNT of Primary acuTe gasTroeNTeriTis Peer reviewed 49 administration the drug should be discontinued for 24 hours to avoid drug accumulation; then treatment can be restarted, if necessary. Metoclopramide Antidopaminergic agents, such as metoclopramide, have both central and peripheral antiemetic effects and are used off-label in dogs and cats. Metoclopramide also stimulates the release of acetylcholine from postganglionic nerves in the peripheral nervous system, which leads to increased gastric contractions and increased gastroesophageal sphincter tone. This promotility effect may also contribute to its antiemetic properties. Metoclopramide can cause neurologic side effects, including excitement and restlessness. The short half-life of this drug necessitates frequent dosing. In our experience, it is most effective when delivered via an IV constant rate infusion but is not as effective as maropitant, ondansetron, or dolasetron. Metoclopramide may not have a direct central antiemetic effect and is a less effective antiemetic agent in cats than in dogs. 7 For this reason, we seldom use it for this purpose in the former unless a prokinetic agent is also indicated. Phenothiazines Phenothiazines, such as chlorpromazine and prochlorperazine, are potent centrally acting antidopaminergics that inhibit the vomiting center and chemoreceptor trigger zone. This class of drug also has antihistaminergic and anticholinergic properties. 8 They are not recommended in hypovolemic patients due to potential for hypotension, and these drugs are not licensed for use in dogs and cats. Phenothiazines can cause mild sedation and are no longer commonly used due to the availability of other effective antiemetic drugs. GASTROPROTECTANTS Sucralfate Sucralfate is a sulfated disaccharide that binds to the acidic moieties of exposed collagen in damaged mucosa, creating a protective barrier against further acid damage. It also stimulates prostaglandin release and cellular proliferation at sites of ulceration and increases mucus production and bicarbonate secretion. Sucralfate is recommended only in cases of suspected gastrointestinal erosion or ulceration, such as those that present with hematemesis or melena. It can interfere with absorption of other drugs, and is typically given at least 2 hours before or after other medications. Famotidine & Ranitidine Famotidine and ranitidine are histamine-2 (H 2 )- receptor antagonists that competitively inhibit histamine-induced acid secretion by the gastric parietal cells. Famotidine is more effective at increasing canine gastric pH compared with ranitidine, but ranitidine also has anticholinesterase activity. This activity may result in some prokinetic action but in studies was only as effective as a saline placebo at increasing gastric pH in dogs and cats; thus, it is not recommended for its acid-suppressing effects. 9,10 H 2 -receptor antagonists are less effcacious than proton pump inhibitors (PPIs) in vivo, but the degree of gastric acid inhibition necessary for therapeutic effect is unknown. H 2 -receptor antagonists may also have cytoprotective properties. 11,12 Omeprazole & Pantoprazole Omeprazole and pantoprazole are PPIs that irreversibly inhibit acid production by gastric parietal cells. This class of drug is more effcacious and has a longer duration of activity than H 2 -receptor antagonists; it may also exert a cytoprotective effect by enhancing prostaglandin synthesis. 9-11,13 In dogs and cats, twice-daily dosing of omeprazole is more effective at reducing gastric acid secretion than once-daily administration. 9,10 Coadministration of famotidine and pantoprazole does not seem to be any more effective than therapy with pantoprazole alone and, thus, there is no beneft in using a H 2 -receptor antagonist for the frst 24 hours of therapy. 14 Because of this, PPIs are the preferred treatment for dogs and cats known or suspected to have esophageal or gastroduodenal ulceration. 11,14 Anecdotally, some dogs and cats with acute gastroenteritis, but no other fndings that indicate gastroduodenal ulceration, such as hematemesis or melena, appear to respond favorably to acid- suppressing drugs. However, use of these drugs has not proven benefcial in any studies in dogs and cats with uncomplicated gastroenteritis; thus, they are not routinely recommended for brief episodes. In humans, long-term use of PPIs has been associated with such side effects as cobalamin defciency, iron defciency, hypomagnesemia, increased susceptibility to pneumonia, enteric infections, fractures, hypergastrinemia, and cancer. 15 To our knowledge, other than hypergastrinemia, the side effects described above have not been reported in dogs and cats receiving long-term treatment with PPIs.