Prochlorperazine

Prochlorperazine is a phenothiazine derivative used primarily as an antiemetic and, in some settings, as an antipsychotic. It functions as a dopamine D2 receptor antagonist with high affinity for receptors in the chemoreceptor trigger zone of the brain, producing antiemetic effects, and with activity in the nigrostriatal pathway that can lead to extrapyramidal symptoms. Additional antihistaminic, anticholinergic, and alpha-adrenergic blocking properties contribute to its sedative effects and potential for orthostatic hypotension.

Medical uses

Prochlorperazine is employed to treat and prevent nausea and vomiting due to surgery, chemotherapy, gastroenteritis, and other conditions. It is also used for vertigo and, less commonly, for acute agitation or psychosis in certain clinical situations. It is generally not a first-line agent for chronic psychiatric conditions due to the risk of motor side effects.

Administration and pharmacology

The drug is available in oral, rectal, and parenteral (intramuscular or, less commonly, intravenous) forms. Onset of antiemetic effect typically occurs within 15–60 minutes after oral dosing or more rapidly after parenteral administration; effects last for several hours, depending on formulation and dose.

Contraindications and precautions

Prochlorperazine should not be used in coma or severe CNS depression, known hypersensitivity, or porphyria. Caution is advised in the elderly, patients with Parkinson disease or other movement disorders, glaucoma, prostatic hyperplasia, seizure disorders, and conditions that may predispose to hypotension. Use in children is limited and generally avoided in very young patients where not specifically indicated.

Adverse effects and safety

Common side effects include drowsiness, dizziness, dry mouth, and constipation. Extrapyramidal symptoms (dystonia, akathisia, parkinsonism) and tardive dyskinesia may occur, particularly with long-term use. QT interval prolongation and rare cardiac arrhythmias have been reported. Neuroleptic malignant syndrome is a rare but serious risk.

Pregnancy and brand names

Prochlorperazine is generally categorized as pregnancy category C; it should be used in pregnancy only if clearly needed. Brand names include Compazine and Stemetil, among others.