Acepromazine is a phenothiazine derivative antipsychotic drug. It was first used in humans in the 1950s,[1] 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 extensively in horses, dogs, and cats; especially as a preanesthetic agent often in conjunction with etorphine, as immobillon. Its potential for cardiac effects 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.