High Quality Content by WIKIPEDIA articles! Acepromazine or acetylpromazine (more 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. It was first used in humans in the 1950s, but is now little used in humans (the closely related analogue, chlorpromazine, is still used as an antipsychotic in humans). Acepromazine is frequently used in animals as a sedative and antiemetic. Its principal value is in quietening and calming anxious animals. The standard pharmaceutical preparation, acepromazine maleate, is used in veterinary medicine in dogs, and cats. Its use in horses has fallen out of favor due to the risk of paraphimosis and persistent priapism in stallions. Its potential for cardiac effects, namely hypotension, can be profound and as such is not recommended for use in geriatric or debilitated animals, especially dogs. In these cases it is most often substituted with midazolam or diazepam and left out of the preanesthetic medication altogether.