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Assessing dexmedetomidine for inducing vomiting in cats

Thawley VJ, Drobatz KJ. Assessment of dexmedetomidine and other agents for emesis induction in cats: 43 cases (2009-2014). J Am Vet Med Assoc. 2015 Dec 15;247(12):1415-8. 

Cats, like children and other animals, have a tendency to eat things they shouldn’t. These include poisons, plants, string, toys or other materials. Some of these substances have the potential to cause serious and even life threatening damage, whether by acting as a toxin, causing physical trauma to the intestinal tract, or leading to intestinal obstruction or plication.

In many circumstances, induction of vomiting can be an important first step in managing inappropriate ingestion. Non-caustic toxins may be expelled from the body prior to absorption as part of the decontamination process. Some physical objects may be expelled prior to causing obstruction.

In canines, vomiting can often be induced by use of apomorphine, a dopamine antagonist. Vomiting in cats is mediated by α receptors rather than dopamine, and as such apomorphine is largely ineffective. Common alternatives include xylazine (an α2 agonist), medetomedine or dexmedetomedine (newer α2 agonists) or irritant agents such as hydrogen peroxide and syrup of ipecac. Despite these options, cats have a reputation for being significantly more difficult to induce vomiting in than dogs.

Physical irritants are generally not recommended in cats due to the high risk of side effects. Syrup of ipecac may cause damage to the heart and is no longer commonly available. Hydrogen peroxide causes irritation of the stomach lining and may lead to hemorrhagic gastritis and esophagitis.

The purpose of this study was to evaluate the efficacy of induction of vomiting using dexmedetomedine, hydrogen peroxide, or xylazine. The study was designed as a retrospective case-control trial involving cats presenting to the University of Pennsylvania from 2009 to 2014.  43 cats were enrolled into three groups as described above.

The median dose of xylazine administered was 0.44mg/kg, IV in 23 cats and IM in 1. The median dose of dexmedetomedine was 7.0ug/kg, 7 IV and 9 IM. 1.5-2mL/kg hydrogen peroxide was administered PO in 3 cats.

The most effective agent for inducing emesis was dexmedetomedine, causing 13 of 16 cats to vomit. No difference was seen in IV vs IM administration  Xylazine had middling efficacy, at 11 of 25 cats. Peroxide was the least effective, with none of the treated cats successfully vomiting (however, only 3 cats were administered peroxide, a very small number). As α2 agonist medications are sedatives, side effects of these medications are largely limited to sleepiness, low blood pressure, bradycardia, and other predictable effects of these medications. Significant advantages exist in the use of these drugs, as they are readily reversed using yohimbine or atipamazole.

While this study provides a good foundation in an important area of medication, there is room for further work. Though dexmedetomedine appears to be the most effective option for emesis induction, combination protocols are commonly used in veterinary practice (ie. co-administration of an opioid and α2 agonist), as are numerous anecdotal techniques (ie. feeding prior to emesis induction). (MRK)

See also:
Lee JA. Emergency management and treatment of the poisoned small animal patient. Vet Clin North Am Small Anim Pract 2013;43:757–771.