Functional classification: Tranquilizer, phenothiazine tranquilizer
Acepromazine inhibits central dopaminergic receptors to produce sedation and tranquilization. Acepromazine also has anti-muscarinic action and blocks norepinephrine at adrenergic receptors (e.g., alpha-receptors). Because of the blockade of alpha-receptors on vascular smooth muscle it also produces vasodilation.
Indications and Clinical Uses
Acepromazine is used as a sedative, a tranquilizer, a pre-anesthetic, and an anesthetic adjunct. In small animals, acepromazine can produce antiemetic effects. For some indications, the administration also produces vasodilation. In horses for treatment of laminitis, it has increased the arterial digital blood flow after a dose of 0.02-0.04 mg/kg.
Adverse Reactions and Side Effects
Sedation and ataxia are common side effects. Extrapyramidal effects (involuntary muscle movements), twitching, dystonia, or Parkinson-like effects are rare but are possible with the administration of phenothiazines to animals.
Phenothiazines may produce excessive vagal tone in some animals. This may be especially prominent in brachycephalic breeds. Administration of atropine may be used to treat the signs of high vagal tone. Because of alpha-adrenergic antagonism, hypotension is possible in animals. In horses, persistent penile prolapse has been reported from use. This effect in horses is unpredictable and apparently not related to dose.
Contraindications and Precautions
Use cautiously in animals that are prone to seizures. However, a risk of seizures in animals from administration of acepromazine may not be as much of a risk as once thought. Seizures were not reported to be a clinical problem in retrospective studies of patients who had seizures. Do not use in animals that have problems with dystonia or that have had extrapyramidal effects from use of phenothiazines.
Phenothiazines can cause hypotension (via alpha-receptor blockade); therefore, use cautiously with other hypotensive drugs or in conditions that may exacerbate hypotension. In pregnancy it produced only minor reduction in blood flow and oxygen delivery to the fetus when used in late pregnancy in cows.
Acepromazine may potentiate other drugs that cause vasodilation. Acepromazine may increase the risk of seizures if administered with other drugs that lower seizure threshold, but this may not be as much of a risk as once thought. Acepromazine has been used to sedate dogs for glucose tolerance testing (0.1mg/kg), without adversely affecting the results.
Instructions for Use
Acepromazine can be administered PO, IV, or IM. When used with general anesthetics, lower doses of general anesthetics can be used, especially when administering barbiturates and inhalant anesthetics. Clinical signs from acepromazine administration are most prominent during the first 3-4 hours after administration but may persist for 7 hours.
Patient Monitoring and Laboratory Tests
Monitor blood pressure in animals susceptible to hypotension. Acepromazine does not affect adrenal function testing in dogs.
Acepromazine is available in 5-, 10-, and 25-mg tablets and in a 10 mg/mL injection. Acepromazine oral granules and powder are available in Canada.
Stability and Storage
Store in a tightly sealed container, protected from light, and at room temperature. Stability of compounded formulations has not been investigated.
Small Animal Dosage
• 0.025-0.1 mg/kg IM, IV, or SQ in a single dose (most common is 0.025 mg/kg). Do not exceed 3 mg total in dogs.
Sedation: 0.5-2.2 mg/kg q6-8h PO.
• 0.025-0.1 mg/kg IM, IV, or SQ in a single dose.
Sedation: 1.1-2.2 mg/kg q6-8h PO.
Large Animal Dosage
• 0.04-0.1 mg/kg IM, q 6-12h, but frequent dosing is not recommended and an interval of 36-48 hours between doses is recommended. For perioperative use, 0.01-0.05 mg/kg, IM, SQ, or IV.
• 0.13-0.26 mg/kg PO, 0.03-0.1 mg/kg IM, or 0.01-0.02 mg/kg IV.
• Adult: 0.03-0.2 mg/kg IV, IM, SQ (single dose).
Withdrawal times: It has been estimated that for extralabel use, establish a withdrawal time of at least 7 days for meat and 48 hours for milk. Canada: 7 days for meat; 48 hours for milk. RCI Classification: 3
Trade and other names: ACE, Aceproject, Aceprotabs, Atravet, and Promace; it sometimes is called acetylpromazine.