Prochlorperazine
Prochlorperazine (base, edisylate, maleate)
Also known as: Compazine · Compro · Prorazin · Stemetil · Tementil · chlormeprazine · prochlorpemazine
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 | IM or SC | q8h | — | 🌎 NA |
| As an antiemetic | 0.1 mg/kg | IM | q6-8h | — | 🌎 NA |
| As an antiemetic | 0.1-0.5 mg/kg | IM or SC | q6-8h | — | 🌎 NA |
| All uses (motion sickness, emesis) | 0.1-0.5 mg/kg | IV/IM/SC | q6-8h | — | 🌍 EU |
| All uses (motion sickness, emesis) | 0.5-1 mg/kg | PO | q8-12h | — | 🌍 EU |
- As an antiemetic: Ensure adequate hydration
- As an antiemetic: Use with extreme caution in dehydrated or hypotensive animals
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an antiemetic | 0.5 mg/kg | SC or IM | three times a day | — | 🌎 NA |
| As an antiemetic | 0.5 mg/kg | IM or SC | q8h | — | 🌎 NA |
| As an antiemetic | 0.1-0.5 mg/kg | IM or SC | q6-8h | — | 🌎 NA |
| All uses (motion sickness, emesis) | 0.1-0.5 mg/kg | IV/IM/SC | q6-8h | — | 🌍 EU |
| All uses (motion sickness, emesis) | 0.5-1 mg/kg | PO | q8-12h | — | 🌍 EU |
- As an antiemetic: Ensure adequate hydration
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Prochlorperazine is a potent phenothiazine antiemetic used in veterinary medicine primarily to control severe nausea and vomiting in dogs and cats.
Historically, it was widely used in veterinary-specific combination products (such as Darbazine®, which included an anticholinergic), but it is now utilized off-label via human formulations.
Clinical Pearl: Because of its broad receptor antagonism, prochlorperazine is highly effective for centrally mediated vomiting. However, due to its potential to cause significant sedation and alpha-adrenergic blockade (leading to hypotension), it is generally reserved for cases where newer, more targeted antiemetics (like maropitant or ondansetron) are ineffective or unavailable. It also possesses mild sedative and weak anticholinergic properties.
Mechanism of action
Prochlorperazine exerts its antiemetic effects primarily by acting on the brain's emetic center and the Chemoreceptor Trigger Zone (CRTZ). Its broad-spectrum efficacy is due to the antagonism of multiple receptor types:
- Dopaminergic (D2) Antagonism → Blocks dopamine signaling in the CRTZ, providing the primary antiemetic effect.
- Histaminergic (H1) & Cholinergic (M1) Antagonism → Contributes to anti-motion sickness efficacy and mild antispasmodic effects in the GI tract.
- Alpha-1 Adrenergic Antagonism → Causes peripheral vasodilation, which is responsible for the primary adverse effect of hypotension.
It also has strong extrapyramidal effects due to central dopamine blockade in the basal ganglia.
Safety & warnings
Contraindications
- Hypovolemia or dehydration
- Shock
- Tetanus
- Strychnine intoxication
- Hepatic dysfunction (use with caution)
- Cardiac disease (use with caution)
Adverse effects
- Sedation
- Hypotension
- Muscle fasciculations and tremors (extrapyramidal signs)
- Prolactin release
- Depression
- Extrapyramidal reactions (rigidity, tremors, weakness, restlessness)
Precautions
Animals may require lower dosages of general anesthetics following phenothiazine administration. Use cautiously and at smaller doses in animals with hepatic dysfunction, cardiac disease, or general debilitation. Because of hypotensive effects, it is relatively contraindicated in patients with hypovolemia, dehydration, or shock. May exacerbate depression in patients with pre-existing CNS depression. Do not use for tetanus or strychnine intoxication due to extrapyramidal effects. Use with caution in very young or debilitated animals.
Drug interactions
May cause reduced GI absorption of oral phenothiazines
May cause reduced GI absorption of oral phenothiazines
May cause additive CNS depression if used with phenothiazines
Phenothiazines may decrease pressor effects
Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal)
Phenothiazines may potentiate the extrapyramidal effects of metoclopramide
May enhance the hypotensive effects of the phenothiazines; dosages of prochlorperazine may need to be reduced
Phenothiazines should not be given within one month of worming with these agents as their effects may be potentiated
Toxicity of the herbicide paraquat may be increased by prochlorperazine
Metabolism may be decreased if given concurrently with phenothiazines
Toxicity may be enhanced by prochlorperazine
Activity may be enhanced by phenothiazines
Increased blood levels of both drugs may result if administered together
Prochlorperazine may decrease anticoagulant effect
May cause additive CNS depression
May reduce GI absorption of oral phenothiazines
Phenothiazines block alpha-adrenergic receptors, leading to unopposed beta activity causing vasodilation and increased cardiac rate
Monitoring
- Cardiac rate, rhythm, and blood pressure (if indicated and possible to measure)
- Anti-emetic/anti-spasmodic efficacy
- Hydration and electrolyte status
- Body temperature (especially if ambient temperature is very hot or cold)
- Heart rate and rhythm
- CNS status (sedation level, extrapyramidal signs)
- Liver function (with prolonged use)
Pharmacokinetics
Absorption
Little specific information available; likely follows general patterns of other phenothiazine agents.
Distribution
Likely follows general patterns of other phenothiazines. A related compound (chlorpromazine) is detected in maternal milk with a milk-to-plasma ratio of 0.5-0.7 or less.
Metabolism
Hepatic (assumed based on phenothiazine class).
Elimination
Likely follows general patterns of other phenothiazine agents.
Overdose
Overdose generally presents as an exaggeration of adverse effects, particularly profound sedation, hypotension, and extrapyramidal clinical signs (such as torticollis, severe tremors, muscle rigidity, and excessive salivation).
Treatment: Acute extrapyramidal signs have been successfully treated with injectable diphenhydramine in humans. Hypotension should be treated with intravenous fluids; avoid epinephrine due to the risk of "epinephrine reversal" causing further vasodilation.
Available products
Formulations
- Injection (edisylate salt)
- Oral tablets (maleate salt)
- Rectal suppositories (base)
- 12.5 mg/ml injectable solution (1 ml ampoule)
- 3 mg oral tablet
- 5 mg oral tablet
- 5 mg/5 ml oral syrup
Veterinary
- None currently available (Darbazine® is no longer marketed in the USA)
Human-labeled
- Prochlorperazine for Injection: 5 mg/mL in 2 mL vials
- Prochlorperazine Tablets: 5 mg & 10 mg (as maleate)
- Prochlorperazine Suppositories: 25 mg (as base)
- Stemetil 12.5 mg/ml injection
- Stemetil 3 mg tablets
- Stemetil 5 mg tablets
- Stemetil 5 mg/5 ml syrup
Regulatory status
Not a first choice; used off-label under the prescribing cascade as maropitant and metoclopramide are authorized.
POM (Prescription Only Medicine). Used under the cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store in tight, light-resistant containers at room temperature. Avoid temperatures above 40°C and below freezing. A slight yellowing of the oral or injectable solution has no effects on potency or efficacy, but do not use if a precipitate forms or the solution is substantially discolored.
Client information
Important Safety Note: Observe your pet closely for at least one hour following dosing. Keep them in a safe, quiet environment as this medication can cause drowsiness and unsteadiness.
- Dry Mouth: Your pet may experience a dry mouth (often seen as lip smacking). This can be relieved by applying small amounts of water to your pet's tongue for 10-15 minutes.
- Urine Color Change: This medication may harmlessly discolor the urine to a pink or red-brown color; this is normal and not a cause for concern.
- When to Call the Vet: Protracted vomiting and diarrhea can be serious. Contact your veterinarian if clinical signs are not alleviated. Seek immediate veterinary care if your animal exhibits abnormal behavior, becomes rigid, or displays other abnormal body movements or tremors.
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.