Acepromazine, acetopromazine, or acetylpromazine (commonly known as ACP, Ace, or by the trade names Atravet or Acezine 2, number depending on mg/ml dose) is a phenothiazine derivative antipsychotic drug.

[6] Its potential for cardiac effects can be profound, namely hypotension due to peripheral vasodilation, so it should be avoided or used with caution in geriatric or debilitated animals.

[8][9]: 115  Its action at the chemoreceptor trigger zone (in the area postrema) and the solitary nucleus (in the medulla oblongata) allow it to have an antiemetic effect.

For this reason, caution has typically been advised when contemplating acepromazine use in epileptic canine patients, as it was widely believed to lower the seizures threshold.

[20] This may occur only in certain families of boxers, but the unknown risk to an individual dog means that acepromazine should be used at reduced doses, or not at all, in this breed.

[22] In equine surgery, premedication with acepromazine has been shown to reduce the perianaesthetic mortality rate, possibly due to its actions as a sedative and anxiolytic.

While it is shown to elicit vasodilation in the distal limb, evidence showing its efficacy at increasing perfusion in the laminae is lacking.

[24] Side effects are not common, but the use of acepromazine in stallions should be used with caution (but is not absolutely contraindicated) due to the risk of paraphimosis and priapism.

[6] Acepromazine also lowers blood pressure, and should therefore be used with caution in horses that are experiencing anemia, dehydration, shock, or colic.