Just Ask the Expert: Is ace not so ace for examining patients with fear aggression?

2019-05-21
Julia Albright, MA, DVM, DACVB

This veterinary behaviorist says that while acepromazine may make patients more tractable in the clinic, its likely doing nothing to reduce their anxiety.

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Question: Why shouldn't acepromazine be a go-to sedative to help manage fear aggression in dogs during physical examinations? Which medications are good alternatives to consider?

Answer: Psychopharmacology can be a confusing and overwhelming subject in veterinary medicine, in large part due to the wide individual variation in observable effects and the overlap in clinical applications. Another factor is the current paradigm shift from drugs that simply produce behavioral suppression and decreased motor activity to those that have antianxiety properties as well.

Acepromazine is an antipsychotic, a class of drugs originally used to treat psychoses such as schizophrenia in humans by blocking the action of dopamine, a catecholamine neurotransmitter. More specifically, acepromazine is a low-potency phenothiazine neuroleptic drug and, like most of the older antipsychotics used in veterinary medicine (including haloperidol and fluphenazine as well as acepromazine), it blocks all the dopamine pathways responsible for cognition, motivation and motor coordination. Acepromazine affects other physiologic systems as well and can cause cardiovascular, motor and endocrine side effects.

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There are many resources available for specific medication choices and doses as well as for helping the veterinary team and clients create a counterconditioning protocol for long-term improvement.

Though acepromazine is generally safe and can ease handling by blunting behavioral responses, it has fallen out of favor, especially as an oral monotherapy, due to numerous reports of sedation without acceptable reduction in signs of fear or anxiety.

So, to answer the specific question about the use of acepromazine to manage fear-related aggression, acepromazine may make the animal more tractable for handling, but it's unlikely to be addressing the underlying fear. Other medications such as benzodiazepines, gabapentin, the atypical antidepressant trazodone, and norepinephrine release blockers like dexmedetomidine are more likely to create emotional calmness (again, primarily based on body language assessment) with or without sedation.

My clients and consulting general practitioners are looking for the silver bullet tablet to help make veterinary visits go more smoothly. Unfortunately, fast-acting situational oral drugs can have variable effects due to several factors. Most of these drugs have reduced bioavailability compared to other administration routes due to the hepatic first pass effect. In addition, many of our patients are experiencing an extreme level of distress during the average clinic visit, and single administration of most of these medications is simply not effective in the face of such acute physiologic arousal.

In my practice, once we've identified a fearful patient, I have the clients conduct a trial of two to three medications at home-usually some combination of those discussed above. We monitor for gastrointestinal or agitation side effects and adjust doses until we reach the desired clinic effect with few to no side effects. Acepromazine may be one of the medications we use in the cocktail, but that is rare these days.

For most of my aggressive patients, the goal of client-administered pre-visit medications is to produce enough sedation and relaxation to allow the team to administer a low-stress intramuscular injection of additional medications for a more thorough physical exam or other procedures. However, occasionally we feel the patient is comfortable enough to continue our visit with just the oral medications.

Either way, when the patient is calm in the veterinary clinic-and not just still-the team can do what it needs to do to optimize physical health without harming emotional wellbeing. And everyone feels better about that.

Dr. Julia Albright is assistant professor of veterinary behavior and PetSafe Chair of Small Animal Behavioral Research at the University of Tennessee's College of Veterinary Medicine.