Azaperone (Stresnil, Fluoperidol) is a pyridinylpiperazine and butyrophenone neuroleptic drug with sedative and antiemetic effects, which is used mainly as a tranquilizer in veterinary medicine. It is used mainly in pigs and elephants. More rarely it may be used in humans as an antipsychotic drug, but this is uncommon. Use in horses is avoided as adverse reactions may occur. Azaperone acts primarily as a dopamine antagonist but also has some antihistaminic and anticholinergic properties as seen with similar drugs such as haloperidol. Azaperone may cause hypotension and while it has minimal effects on respiration in pigs, high doses in humans can cause respiratory depression which may be why it is rarely used in humans. The most common use for azaperone is in relatively small doses to reduce aggression in farmed pigs, either to stop them fighting or to encourage sows to accept piglets. Higher doses are used for anesthesia in combination with other drugs such as xylazine, tiletamine and zolazepam. Azaperone is also used in combination with strong narcotics such as etorphine or carfentanil for tranquilizing large animals such as elephants.