Chemicals / Complex Chemical Agents/ Chemical:

Acepromazine (Phenothiazine sedative)




Information in this page has been entered to support the current volumes of Wildpro and further information will be added as new volumes are completed. This page is not intended to substitute for the manufacturer's data sheet and the information is not yet complete for all species, or for all contra-indications etc.

CAUTION: Before any pharmaceutical product is used, the manufacturer's data sheet, containing information on uses, dosage and administration, contra-indications, warnings etc., should always be consulted. It is important to remember that licensing of pharmaceutical products for use in a particular species/condition, as well as mandatory meat and milk withdrawal times for food-producing animals, varies between countries and changes with time. Withdrawal times also may vary between different pharmaceutical formulations and depending on route of administration. In the EU, the prescription cascade must be followed (see LCofC1.2H and W564.Apr05.w1); note that specific restrictions apply for food-producing animals. In the USA, FARAD may be consulted regarding residues and meat and milk withdrawal times.

General Chemical Information


Phenothiazine derivative used as a sedative and pre-medication for anaesthesia; also used in the treatment of motion sickness. No analgesic effects. (B121, B373.6.w6)

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Names and Formulae

Type Phenothiazine derivative neuroleptic agent. (B121, B263, B373.6.w6)
Alternative Names
  • 2-acetyl-10-(3-dimethylaminopropyl)phenothiazine. (B121)
  • Acepromazine maleate. (B121, B263)
  • Acetylpromazine. (B263)
  • "ACE". (B263)
  • ACP. (B263)
Chemical Formula --
Chemical Structure --
Molecular Weight --
Related Chemicals Other phenothiazine derivatives. (B263, B373.6.w6)

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Physical Properties / Chemistry


Acepromazine maleate: yellow, crystalline solid or powder, odourless, bitter-tasting. (B121, B263)

Melting point --
Boiling point --
Density --
Water solubility 1 g acepromazine maleate in 27 mL water. (B263)
Other solubility
  • 1 g acepromazine maleate in 13 mL alcohol. (B263)
  • 1 g acepromazine maleate in 3 mL chloroform. (B263)
Acid/Base --

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Pharmacology & General Information

  • In the CNS, blocks post-synaptic dopamine receptors and may inhibit dopamine release and increase dopamine turnover rate. (B263)
  • Phenothiazines "are thought to depress portions of the reticular activating system which assists in the control of body temperature, basal metabolic rate, emesis, vasomotor tone, hormonal blanace, and alertness." (B263)
  • Phenothiazine also have, to varying degrees, anticholinergic, antihistaminic, antispasmodic and alpha-adrenergic blocking effects. (B263)
  • The main desired effect is tranquillisation. (B263)
  • Causes a dose-dependent decrease in haematocrit in horses and dogs (up to 50% in the horse, probably due to increased sequestration of red blood cells by the spleen). (B263)
  • May cause a decrease in respiratory rate. (B263)
  • Lowers arterial blood pressure. Increases central venous pressure, has a vagally-induced bradycardic effect (but this may be negated by reflex tachycardia secondary to blood pressure decrease) and causes transient sinoatrial arrest. (B263)
  • Antidysrhythmic effects: inhibits arrhythmias induced by ultra-short acting barbiturates, also protects against ventricular fibrillation induced by halothane and adrenaline (epinephrine). (B263)
Storage / Stability Protect from light. Store tablets in tight containers. Protect injection from freezing. (B263)
Legal Category (In UK) POM-V.

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Associated Techniques




(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

Authors Nikki Fox BVSc MRCVS (V.w103)
Referees Debra Bourne MA VetMB PhD MRCVS (V.w5)

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Therapeutic Information


  • Sedative. (B373.6.w6)
  • Note: In excited animals there may be no obvious effect. (B373.6.w6)
Appropriate Use --
Limitations No analgesic effect. (B373.6.w6)
Notes --

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Pharmacokinetics and Drug Interactions

Absorption / Bioavailability
  • Variable absorption rate after oral or subcutaneous administration. (B373.6.w6)
  • Following oral administration, some effect may occur within 15 minutes with peak effect after about an hour. (B373.6.w6)
  • Following intravenous injection, peak effect in five minutes. (B373.6.w6)
  • In horses: Following intravenous injection, up to 15 minutes for onset and 30-60 minutes to peak effect. (B263)
Distribution In horses: volume of distribution 6.6 L/kg. (B263)
Plasma Protein binding / Storage In horses: more than 99% plasma protein bound. (B263)
Elimination Route Metabolised in the liver; conjugated and unconjugated metabolites are excreted in urine. (B263, B373.6.w6)
Elimination half-life / Clearance Rate
  • Usually action may be seen for about four hours in a fit, healthy animal given a low dose, but in debilitated individuals, or if a higher dose is given, effects may last as long as 24 hours. (B373.6.w6)
  • In horses: Elimination half-life about three hours. (B263)
Drug Interactions
  • Physical compatibility: Has been mixed with: "atropine, buprenorphine, chloral hydrate, ketamine, meperidine [pethidine], oxymorphone, and xylazine." (B263)
  • Physical incompatibility has been reported between phenothiazines and: diazepam, glycopyrrolate. (B263)
  • "Acepromazine should not be given within one month of worming with an organophosphate agent as their effects may be potentiated." (B263)
  • Additive CNS depression may occur if other CNS depressants are used with acepromazine. (B263)
  • Additive cardiac depression may occur if quinidinee is used with phenothiazines. (B263)
  • GIT absorption of phenothiazines may be decreased by antacids and by antidiarrhoeal mixtures such as kaolin/pectin and bismuth subsalicylate. (B263)
  • If propranolol is given with a phenothiazine, the blood levels of both drugs may be increased. (B263)
  • Metabolism of phenytoin may be decreased if given with a phenothiazine. (B263)
  • Phenothiazines block alpha-adrenergic receptors, therefore if epinephrine (adrenaline)is given, unopposed beta activity could occur resulting in vasodilatation and increased heart rate. (B263)
  • Activity of procaine may be increased by phenothiazines. (B263)

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Formulations available UK:
  • 10 mg and 25 mg tablets (ACP, Novartis). (B373.6.w6)
  • 2 mg/mL and 10 mg/mL injections for cats and dogs, and for horses, respectively. (ACP, Novartis). (B373.6.w6)
  • 35 mg/mL oral gel for horses (Sedalin, Vetoquinol). (B373.6.w6)
Doses / Administration Routes / Frequencies
  • Generally 0.02 - 0.05 mg/kg (20 - 50 micrograms per kg) to give moderate sedation allowing procedures such as intravenous injection or catheterisation of a vein. (B373.6.w6)
  • Cats, dogs: 
    • For sedation/pre-anaesthetic medication, orally 0.25-3.0 mg/kg; 0.03 - 0.125 mg/kg (maximum 4 mg) by subcutaneous, intramuscular or slow intravenous injection. (B373.6.w6)
    • For motion sickness, 0.5 - 1.0 mg/kg orally, 15 - 30 minutes before a light meal. (B373.6.w6)
  • Horses:
    • By mouth, 0.075 - 0.22 mg/kg (75 - 220 micrograms/kg) for sedation (moderate sedation with 0.15 mg/kg). (B373.6.w6)
    • By intramuscular or slow intravenous injection, 0.03 - 0.1 mg/kg (30 - 100 micrograms/kg). (B373.6.w6)

Lagomorphs - Oryctolagus cuniculus domesticus - Domestic rabbit:

  • 1 mg/kg intramuscularly. (B373.Guide.w41)
  • 0.1 - 1.0 mg/kg intramuscularly or subcutaneously. (B546)
  • As a tranquilliser, 1 mg/kg intramuscularly. Effect should start within 10 minutes, lasting 1 -2 hours. (B263)
  • 0.5 - 1.0 mg/kg intramuscularly or subcutaneously, for sedation. (B600.4.w4)
  • 0.5 mg/kg plus butorphanol 0.5 mg/kg, subcutaneously or intramuscularly, for sedation. (B600.4.w4) Note: 
    • Can be given mixed in the same syringe. (B600.4.w4)
    • The combination causes vasodilatation. (B600.4.w4)
  • 0.5 - 1.0 mg/kg intramuscularly. (B602.41.w41)
  • 0.25 - 1.0 mg/kg intramuscularly as a preanaesthetic, sedative or tranquilizer. (B548.w8)
  • 1 - 5 mg/kg subcutaneously or intramuscularly as a preanaesthetic, with the lower end of the dose range preferred. (B548.w8)

Ferrets - Mustela putorius furo - Ferret:

  • 0.1 - 0.5 mg/kg subcutaneously or intramuscularly. (B602.41.w41)
    • Ketamine 20 - 35 mg/kg plus acepromazine 0.20 - 0.35 mg/kg subcutaneously or intramuscularly. (B602.41.w41)
  • 0.1 - 0.3 mg/kg intramuscularly or subcutaneously. (B626.App.w22)
  • 0.1 - 0.25 mg/kg intramuscularly or subcutaneously. As an anaesthetic premedicant. Note: causes hypotension and hypothermia. (J213.3.w1)
    • Ketamine10 - 30 mg/kg plus acepromazine 0.05 - 0.3 mg/kg intramuscularly. Note: hypotension and hypothermia. (J213.3.w1)

Great Apes

Monitoring parameters --

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Withdrawal period / Withholding time

Notes UK: Not for use in horses intended for human consumption. (B373.6.w6)

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Toxic Information

Toxic effects of Pharmaceutical Products

Contraindications / Precautions
  • Not suitable for use as a pre-medication prior to procedures which may promote epileptiform seizures - including myelography as well as pre-medication of animals known to be epileptic. (B373.6.w6)
  • Not suitable in trauma patients which may be hypovolaemic, because it produces hypotension; this can be fatal in association with hypovolaemia. (B373.6.w6)
  • Contraindicated in "Pregnant female animals; lactating mares; epileptics; animals in shock or post trauma or with existing emotional excitation; concurrent hypotensive drugs; procain hydrochloride, or organophosphorus compounds in horses; horses should not be ridden within 36 hours of treatment; equine colic; hypovolaemia. " (B373.6.w6)
  • Use with caution, and decrease dosage, in individuals with general debilitation, hepatic dysfunction, or cardiac disease, and in the very young. (B263)
  • Following use of acepromazine, lower dosages of general anaesthetics may be required. (B263)
  • Relative contraindication in individuals with hypovolaemia or shock. (B263)
Adverse Effects / Side Effects / Warnings
  • Hypotension. (B263, B373.6.w6)
    • Risk of cardiovascular collapse secondary to hypotension and bradycardia. (B263)
  • Thrombocytopaenia. (B373.6.w6)
  • Platelet dysfunction. (B373.6.w6)
  • In cats and dogs, nictitating membrane protrusion. (B373.6.w6)
  • Ataxia, muscle tremors. (B373.6.w6)
  • Hypothermia. (B373.6.w6)
  • In brachycephalic breeds of dogs, may cause syncope. (B373.6.w6)
  • Use with caution in individulas with renal impairment, debilitated individuals, those with anaemia or cardiovascular disease, and large dog breeds. (B373.6.w6)
  • Care in use for car travel, particularly in hot weather. (B373.6.w6)
  • Extrapyramidal side-effects which may be seen at high doses include tremor, rigidity and catalepsy. (B373.6.w6)
  • In male equines, paralysis of the retractor penis muscle and parphimosis may occur. If this drug is given to stallions a low dose rate should be used. (B263, B373.6.w6)
  • Occasional contradictory aggression and general CNS stimulation. (B263)
  • Transient pain may occur localy if given intramuscularly. (B263)
Operator Warnings --
Overdose / Acute Toxicity
  • Monitor, treat symptomatically. (B263)
  • Massive oral overdose: if possible, empty the gut. (B263)
  • If hypotension occurs, treat with phenylephrine or norepinephrine. (B263)
  • If seizures occur, control with diazepam or barbiturates. (B263)
  • To treat CNS depression, doxapram has been suggested. (B263)

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Detailed Toxicological Information

Classification --
Acute Toxicity Mice: LD50 61 mg/kg intravenously, 257 mg/kg orally. (B263)
Chronic Toxicity Dogs: no apparent adverse effects after doses of 20 - 40 mg/kg over six weeks. "Dogs gradually receiving up to 200 mg/kg orally exhibited signs of pulmonary edema and hyperemia of internal organs, but no fatalities were noted." (B263)
Reproductive effects --
Teratogenic effects --
Mutagenic effects --
Carcinogenic effects


Organ toxicity --
Bird Toxicity --
Aquatic organism activity --
Other organism toxicity --

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Nutrient Information

Nutritional Data

Sources --
Biological Use --
Recommended Daily Allowance / Recommended level in food --
Stability in food (Storage time) --
Interactions --

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External / Environmental Information

External / Environmental Uses

Use --
Formulation --
Application method --
Application Concentration --
Persistence of Effect / Frequency of Application --

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Sources in the Environment

Natural sources --
Human-associated sources


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Effects on the Environment

Effects in the aquatic environment


Effects on land --

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Persistence in the Environment

Breakdown in soil and groundwater


Breakdown in water --
Breakdown in vegetation --

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