Acepromazine is one of the most commonly used tranquilizers in veterinary medicine. It is a phenothiazine compound. Its mode of action is only partially understood but it involves blockage of dopamine nerve receptors in the brain. It causes tranquilization and also has an anti-emetic effect. This makes it especially useful for treating car sickness, since that is often a combination of fear and motion sickness in dogs.

The recommended dosage for acepromazine is 0.25mg to 1mg per pound of body weight. In most cases it is not necessary to use the higher dosages. That is not true for use in trying to control fear based aggression. Acepromazine is considered to be very safe. The average toxic dose is significantly higher than the recommended dosage (at least 20 times the dose). Despite this, acepromazine does have some significant effects that must be considered. It can cause hypotension (lowering of blood pressure). This effect may be exaggerated in Boxers and there have been anecdotal reports of death of Boxers after the use of acepromazine. In addition, acepromazine seems to make it easier for dogs with seizure disorders to have a seizure. This medication should not be used near the time of dipping or treatment with organophosphates for flea control.

Acepromazine doesn't have any pain-killing effects. Many dogs seem to be able to will themselves to overcome its effects, at least temporarily. This makes it less than ideal as a drug for dealing with aggressive or fearful dogs but there have not been better alternatives for medicating prior to the visit. It works often enough that many vets will try this approach first. We do this when we think it has a chance of helping make an office visit go easier. We just remember to continue to be very careful when examining the dog.