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Dexmedetomidine versus xylazine as an emetic in cats | VETgirl Veterinary Continuing Education Podcasts

We all know how difficult it can be to make a cat vomit when we actually need for them to vomit. Veterinary emergency hospitals are encouraged to stock formulations of apomorphine for inducing emesis in dogs, but sadly this medication doesn’t seem to work in cats. The theorized reason behind the feline’s lack of robust emetic response to apomorphine stems from anatomical differences in their chemoreceptor trigger zone receptors where they are believed to favor more of the alpha-2 receptors over the dopamine receptor abundance that dogs exhibit. For this reason, most hospitals carry xylazine, an alpha-2 adrenergic agonist more commonly used in large animal anesthesia. However, if you’ve ever tried to make a cat vomit using xylazine, their response is variable and many will not vomit when appropriate doses are used. Clinically, I’ve always felt like it only works half the time in my poisoned cat patients!

So what does your hospital use to induce emesis in cats?

In this VETgirl online veterinary continuing education podcast, we review dexmedetomidine versus xylazine as an emetic in cats. BTW, remember that you shouldn’t use hydrogen peroxide in cats, as it can result in severe hemorrhagic gastritis (1).

So, Thawley and Drobatz (2) out of University of Pennsylvania School of Veterinary Medicine wanted to evaluate which emetic agent to use in cats. In a retrospective study called “ Assessment of dexmedetomidine and other agents for emesis induction in cats: 43 cases (2009-2014),” the authors reviewed records between 2009 and 2014 at the Matthew J. Ryan Veterinary Hospital at the University of Pennsylvania to assess whether emesis in cats was successful when using dexmedetomidine, xylazine, or hydrogen peroxide. They also looked at the time it took until production of emesis after the emetic agent was administered to the patient. A total of 43 cats were evaluated. In this study, the reasons for emesis induction were mostly related to toxin ingestion (e.g., lilies, rodenticide, NSAIDs), but string ingestion was also a relatively common cause (remember, we don’t typically induce emesis if it’s a linear foreign body – only when it’s recent ingestion and that we confirmed that the linear foreign body is NOT in the duodenum or there is no plication seen on radiographs!).

In this study, hydrogen peroxide was administered to 3 (7%) of the cats at standard canine dosing of 1.5 to 2.0 ml/kg, and was ultimately unsuccessful at inducing emesis in all 3 cats. Again, please stop using hydrogen peroxide in cats, yo. Xylazine was administered at a median dose of 0.44 mg/kg to 25 (58%) of cats. Most of the cats received the xylazine intramuscularly, but one cat received the drug intravenously. (BTW, be careful doing that as it makes them really, really sedate and hypotensive). In the cats that received xylazine, emesis induction was successful in 11 (44%) of the 25 cats; this fits with my clinical experience of it only working half the time! Dexmedetomidine was administered to 16 (37%) of cats with roughly half of these cats receiving a median dose of 7 mcg/kg intramuscularly and the other half receiving a median dose of 3.5 mcg/kg intravenously. Emesis induction was successful in 13 (81%) of the 16 cats induced with dexmedetomidine. For the 3 cats with unsuccessful emesis induction with dexmedetomidine, their median doses were a bit lower than the average IV dose at about 2 mcg/kg IV, but a statistical significance difference between the successful and unsuccessful IV doses was not found. When in doubt, go bigger. Interestingly, although the study did not show statistical significance between IV and IM administration of dexmedetomidine, all cats that were given IM dexmedetomidine vomited, whereas only 6 of 9 cats administered IV dexmedetomidine vomited. This suggests that perhaps IM administration is the best route to give to induce emesis in cats.

Thawley and Drobatz also found that the elapsed time between drug administration and successful emesis for xylazine was 10 minutes and for dexmedetomidine was 5 minutes, though these results were not found to be statistically different. (Even better for us inpatient emergency critical care types!). The only adverse effects reported from the emesis induction agents was sedation following induction with xylazine in 2 cats, and sedation following induction in 1 cat with dexmedetomidine; these cats were all successfully reversed with yohimbine or atipamezole respectively.

So, what can we take away from this VETgirl podcast? For cats, dexmedetomidine and xylazine hydrochloride, alpha adrenergic agonists, are centrally-acting emetic agents that work on the alpha receptors of the chemoreceptor trigger zone and are much safer on the gastrointestinal tract as compared to hydrogen peroxide. Based off this study, dexmedetomidine outperformed xylazine and hydrogen peroxide when used for the purpose of inducing emesis in cats. Keep in mind that the use of apomorphine and hydrogen peroxide are not recommended for cats, as they are ineffective or can result in severe adverse effects (e.g., hemorrhagic gastritis), respectively.

BTW for dogs: Xylazine does not reliably produce an emetic response in dogs, and thus is not recommended as an emetic agent. We prefer apomorphine or hydrogen peroxide in dogs. As for adverse effects associated with alpha-adrenergic drugs in cats, they can include bradycardia, sedation, tremors, and respiratory depression (3,4). Overall, Thawley and Drobatz found that dexmedetomidine (7 mcg/kg, IM) resulted in emesis approximately 80% of the time in cats, as compared to only about 44% of the time in cats with xylazine (2). A similar study by Willey et al also supported similar findings (5). Alpha adrenergic agonists should not be used in cats that have ingested certain medications (e.g., other alpha-adrenergic agonist drugs) or products that may result in compounding of bradycardia, respiratory depression, sedation, or CNS depression symptoms (3,4), btw.

Possible concerns when using an alpha-2 agonist such as xylazine or dexmedetomidine are their cardiovascular effects as they can cause peripheral vasoconstriction and reflex bradycardia, but this study did not evaluate the safety of these agents due to lacking information in the available medical records. Fortunately, both agents have effective reversals, so theoretically if a cat were to exhibit concerning signs related to blood pressure or arrhythmias, the patient could be fully reversed (of course, that’s after we’ve drawn blood work, placed the IV catheter, etc.).

Overall, the authors concluded that dexmedetomidine was more successful at emesis induction and theorized a possible reason for this may be that dexmedetomidine may exhibit a stronger alpha-2 adrenergic receptor selectivity than xylazine. VETgirl agrees – dexmedetomidine has proven more effective at inducing emesis in cats than xyalzine in the ER setting following toxin ingestion based on my clinical experience too! This study helps pave the way for a more effective emetic agent to become utilized more readily in the emergency situation for our tricky feline friends. NOTE: The authors point out that this study only focuses on whether emesis was successful or not following administration of hydrogen peroxide, xylazine, or dexmedetomidine, but specify that not all successful events of emesis can effectively eliminate the offending toxin or foreign material. So while we know what emetic agent to now use in cats, just be aware, this study didn’t assess how well they vomited up their foreign body or toxicant!

When in doubt, contact the ASPCA Animal Poison Control Center for life-saving advice!

References
1. Obr TD, Fry JK, Lee JA, et. al. Necroulcerative hemorrhagic gastritis in a cat secondary to the administration of 3% hydrogen peroxide as an emetic agent. J Vet Emerg Crit Care 2017;27(5):605-608.
2. 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;247(12):1415-1418.
3. Lee JA. Decontamination of the Poisoned Patient. In: Osweiler G, Hovda L, Brutlag A, Lee JA, ed. Blackwell’s Five-Minute Veterinary Consult Clinical Companion: Small Animal Toxicology, 1st Ed. Iowa City: Wiley-Blackwell, 2010, pp. 5-19.
4. Peterson ME. Toxicological Decontamination. In: Peterson ME, Talcott PA, ed. Small Animal Toxicology, 2nd Ed. St. Louis: Elsevier Saunders, 2006, pp. 127-141.
5. Willey JL, Julius TM, Claypool SPA, et al. Evaluation and comparison of xylazine hydrochloride and dexmedetomidine hydrochloride for the induction of emesis in cats: 47 cases (2007–2013). J Am Vet Med Assoc 2016;248(8):923-928.

Abbreviations:
IM- intramuscular
IV- Intravenous

  1. I love the podcasts and have just figured out how to listen to them in the car. Thanks for putting together a succinct and informative method of CE!

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