Chlorpromazine
Chlorpromazine Hydrochloride
Also known as: Thorazine · aminazine · chlorpromazini hydrochloridum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an antiemetic | 0.5 mg/kg IV, IM or SC three to four times daily | IV/IM/SC | q6-8h | — | 🌎 NA |
| As an antiemetic | 0.2-0.4 mg/kg SC, IM q8h | SC/IM | q8h | — | 🌎 NA |
| As an antiemetic | 4-8 mg (total dose; do not exceed 0.5 mg/kg) per dog PO q12h | PO | q12h | — | 🌎 NA |
| As a muscle relaxant during tetanus | 2 mg/kg IM twice daily | IM | q12h | — | 🌎 NA |
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an antiemetic | 0.5 mg/kg IV, IM or SC three to four times daily | IV/IM/SC | q6-8h | — | 🌎 NA |
| As an antiemetic | 2 mg (total dose) per cat PO q12h | PO | q12h | — | 🌎 NA |
| As a preanesthetic | up to 1.1 mg/kg IM 1-1.5 hours prior to surgery | IM | Once | — | 🌎 NA |
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Premedication for cattle undergoing standing procedures | Up to 1 mg/kg IM | IM | Once | — | 🌎 NA |
- Premedication for cattle undergoing standing procedures: May cause regurgitation if animal undergoes general anesthesia
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Premedication | 1 mg/kg IM | IM | Once | — | 🌎 NA |
| Premedication | 0.55-3.3 mg/kg IV; 2-4 mg/kg IM | IV/IM | Once | — | 🌎 NA |
| Restraint | 1.1 mg/kg IM | IM | Once | — | 🌎 NA |
| Prior to barbiturate anesthesia | 2-4 mg/kg IM | IM | Once | — | 🌎 NA |
- Restraint: Effects are at peak in 45-60 minutes
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General use | 0.55-4.4 mg/kg IV, 2.2-6.6 mg/kg IM | IV/IM | Once | — | 🌎 NA |
Goats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| General use | 0.55-4.4 mg/kg IV, 2.2-6.6 mg/kg IM | IV/IM | Once | — | 🌎 NA |
| General use | 2-3.5 mg/kg IV q5-6h | IV | q5-6h | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Chlorpromazine is the prototype phenothiazine derivative, historically used as a neuroleptic and tranquilizer in veterinary medicine, though largely supplanted by acepromazine for these purposes due to acepromazine's higher potency and shorter duration of action.
Currently, it is primarily utilized for its antiemetic properties in small animals, particularly for managing motion sickness in cats.
Key Clinical Points:
- Effectively inhibits apomorphine-induced emesis in dogs (but not cats) and morphine-induced emesis.
- Does not inhibit emesis caused by copper sulfate or digitalis glycosides.
- Possesses negligible analgesic effects; appropriate analgesia must be provided for painful conditions.
- Generally contraindicated in horses due to paradoxical excitation and ataxia.
- Can cause significant vasodilation and hypotension; patients must be adequately hydrated prior to administration.
Mechanism of action
Chlorpromazine acts primarily as a dopamine (D2) receptor antagonist in the central nervous system.
- Antiemetic effect: Blocks D2 receptors in the Chemoreceptor Trigger Zone (CRTZ) of the medulla → inhibits emetic signaling to the vomiting center.
- Sedative effect: Antagonizes central histamine (H1), alpha-1 adrenergic, and dopamine receptors → depresses the reticular activating system.
- Cardiovascular effect: Peripheral alpha-1 adrenergic blockade → vasodilation and potential hypotension.
- Also possesses weak anticholinergic (muscarinic M1 blockade) and antiserotonergic properties.
Safety & warnings
Contraindications
- Horses (generally not recommended due to severe ataxia and panic reactions)
- Rabbits (IM injection causes severe muscle discomfort and swelling)
- Hypovolemia or shock
- Tetanus or strychnine intoxication (due to extrapyramidal effects)
Adverse effects
- Hypotension
- CNS stimulation (paradoxical)
- Bradycardia or tachycardia
- Extrapyramidal signs in cats (tremors, shivering, rigidity, loss of righting reflexes)
- Lethargy
- Diarrhea
- Loss of anal sphincter tone
- Ataxia, excitation, and panic reactions in horses
- Hypothermia or hyperthermia
Precautions
Important: Intravenous injections must be diluted with saline to concentrations of no more than 1 mg/mL and administered slowly. Do not inject into arteries.
- MDR1 Mutation: Dogs with MDR1 mutations (Collies, Australian Shepherds, etc.) may develop pronounced and prolonged sedation. Reduce initial doses by 25% in suspect patients.
- Aggressive Dogs: Use cautiously as a restraining agent; it may make the animal more prone to startle and react to noises or sensory inputs.
- Debilitated Patients: Use cautiously and in smaller doses in animals with hepatic dysfunction, cardiac disease, or general debilitation.
- Anesthesia: Animals may require lower dosages of general anesthetics following phenothiazines.
Drug interactions
Possible increased risk for hypothermia
May cause reduced GI absorption of oral phenothiazines
May cause reduced GI absorption of oral phenothiazines
May cause additive CNS depression
May cause serious hypothermia
Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal)
May enhance hypotensive effects; chlorpromazine dosages may need reduction
Effects may be potentiated; do not give phenothiazines within one month of worming with these agents
Toxicity may be increased by chlorpromazine
Metabolism may be decreased if given concurrently
Toxicity may be enhanced by chlorpromazine
Activity may be enhanced by phenothiazines
Increased blood levels of both drugs may result
May cause additive cardiac depression
Monitoring
- Cardiac rate, rhythm, and blood pressure (if indicated and possible)
- Degree of tranquilization and anti-emetic activity
- Body temperature (especially in extreme ambient temperatures)
Pharmacokinetics
Absorption
Absorbed rapidly after oral administration, but undergoes extensive first pass metabolism in the liver. Well absorbed after IM injection, but onset of action is slower than IV.
Distribution
Distributed throughout the body; brain concentrations are higher than plasma. Approximately 95% is bound to plasma proteins (primarily albumin).
Metabolism
Extensively metabolized principally in the liver and kidneys.
Elimination
Little specific information is available regarding its excretion in dogs and cats.
Overdose
Small overdoses typically cause somnolence. Larger overdoses can cause serious effects including coma, agitation/seizures, ECG changes/arrhythmias, hypotension, and extrapyramidal effects.
- Treatment: Most overdoses are managed with supportive care and monitoring. Massive oral overdoses should be treated by emptying the gut if possible.
- Hypotension Management: Do NOT treat hypotension with epinephrine (due to epinephrine reversal). Use phenylephrine or norepinephrine (levarterenol).
- Seizure Management: Control seizures with barbiturates or diazepam.
Available products
Formulations
- Oral Tablets
- Injection
- Oral Solution
Human-labeled
- Chlorpromazine Oral Tablets: 10 mg, 25 mg, 50 mg, 100 mg & 200 mg
- Chlorpromazine Injection: 25 mg/mL in 1 & 2 mL amps
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Protect from light and store at room temperature. Avoid freezing the oral solution and injection. Dispense oral solution in amber bottles. Store oral tablets in tight containers. Do not store in plastic syringes or IV bags for prolonged periods as the drug may adsorb to plastic. Discard darkly colored solutions or if precipitates have formed (a slight yellowish color will not affect potency).
Client information
- Handling: Avoid getting the liquid solution on your hands or clothing, as it can cause contact dermatitis (skin irritation). Wash hands after administration.
- Urine Color: This medication may discolor your pet's urine to a pink or red-brown color. This is a normal side effect and is not a cause for concern.
- Observation: Keep your pet in a safe, quiet environment while sedated. Watch for excessive lethargy, unusual muscle tremors, or stiffness, and contact your veterinarian if these occur.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.