Phenothiazines

Actions

Phenothiazines have tranquilising, sedative and anxiolytic properties, but do NOT provide analgesia. As well as these effects on the CNS, phenothiazines also affect the cardiovascular system and the gastrointestinal tract (see Side Effects and Contraindications).

Drugs in this Group

Phenothiazines include:

• Acepromazine
• Proprionylpromazine
• Chlorpromazine
• Promazine
• Methotrimeprazine
• Promethazine

Acepromazine

Acepromazine is commonly used in veterinary practice as a sedative and as a premedicant. It is available in liquid, gel and tablet form and so may be administered orally (with 20-55% bioavailability), i/m, i/v or s/c. The intramuscular route is preferred as fewer side effects are apparent. Administration in this way leads to a 20 minute onset of drug action. The time to onset is only 5 minutes if acepromazine is given intravenously, but the drug must be given slowly to avoid causing vasodilation and hypotension. The duration of effects is 4-6 hours.

Methotrimeprazine

Methotrimeprazine has potent analsgesis as well as tranquilising, sedatice and anxiolytic actions. It si a component of small animal immobilon, along with etorphine.