Prochlorperazine
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.
Mecanismo: 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.
Dosificación por especie
- As an antiemetic · 0.5 mg/kg · SC or IM · three times a day · Ensure adequate hydration
- As an antiemetic · 0.5 mg/kg · IM or SC · q8h
- As an antiemetic · 0.1-0.5 mg/kg · IM or SC · q6-8h
- All uses (motion sickness, emesis) · 0.1-0.5 mg/kg · IV/IM/SC · q6-8h
- All uses (motion sickness, emesis) · 0.5-1 mg/kg · PO · q8-12h
- As an antiemetic · 0.5 mg/kg · IM or SC · q8h · Ensure adequate hydration
- As an antiemetic · 0.1 mg/kg · IM · q6-8h · Use with extreme caution in dehydrated or hypotensive animals
- As an antiemetic · 0.1-0.5 mg/kg · IM or SC · q6-8h
- All uses (motion sickness, emesis) · 0.1-0.5 mg/kg · IV/IM/SC · q6-8h
- All uses (motion sickness, emesis) · 0.5-1 mg/kg · PO · q8-12h
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Hypovolemia or dehydration
- Shock
- Tetanus
- Strychnine intoxication
- Hepatic dysfunction (use with caution)
- Cardiac disease (use with caution)
Efectos adversos
- Sedation
- Hypotension
- Muscle fasciculations and tremors (extrapyramidal signs)
- Prolactin release
- Depression
- Extrapyramidal reactions (rigidity, tremors, weakness, restlessness)
Interacciones farmacológicas
- Antacids · May cause reduced GI absorption of oral phenothiazines · moderate
- Antidiarrheal mixtures (e.g., Kaolin/pectin, bismuth subsalicylate) · May cause reduced GI absorption of oral phenothiazines
- CNS Depressant Agents (barbiturates, narcotics, anesthetics) · May cause additive CNS depression if used with phenothiazines
- Dopamine · Phenothiazines may decrease pressor effects
- Epinephrine · Phenothiazines block alpha-adrenergic receptors; concomitant epinephrine can lead to unopposed beta-activity causing vasodilation and increased cardiac rate (epinephrine reversal)
- Metoclopramide · Phenothiazines may potentiate the extrapyramidal effects of metoclopramide
- Opiates · May enhance the hypotensive effects of the phenothiazines; dosages of prochlorperazine may need to be reduced
- Organophosphate Agents · Phenothiazines should not be given within one month of worming with these agents as their effects may be potentiated
- Paraquat · Toxicity of the herbicide paraquat may be increased by prochlorperazine
- Phenytoin · Metabolism may be decreased if given concurrently with phenothiazines
- Physostigmine · Toxicity may be enhanced by prochlorperazine
- Procaine · Activity may be enhanced by phenothiazines
Monitorización
- 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
- Blood pressure
- CNS status (sedation level, extrapyramidal signs)
- Liver function (with prolonged use)
Sobredosis
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.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.