D2 Antagonist·Gastrointestinal - Antiemetics

proCHLORPERazine

Nausea and vomiting, vertigo, Meniere's disease

PBSANTIEMETICStemetil, Stemzine5 mg tabletS4+1

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At a glance

Max Dose

20 mg/day

Half-life

6-8 h

Caution: EPSE / Akathisia

RISK

Caution: Sedation

COMMON

Cautions

Avoid / Cautions

Parkinson's disease, severe CNS depression, known hypersensitivity to phenothiazines. Pregnancy Category C. (Avoid late in pregnancy to prevent neonatal EPSE).

Where it stands

Rapid Summary

Overview

Phenothiazine antiemetic and antipsychotic. Highly effective central dopamine antagonist. The traditional drug of choice for vertigo and severe labyrinthitis.

Clinical Focus

Like Metoclopramide, it blocks D2 receptors and can cause severe extrapyramidal side effects (EPSE), including acute dystonia in young patients.

Bottom Line

Prochlorperazine is a phenothiazine antiemetic effective for nausea, vertigo, and migraine, but causes extrapyramidal side effects and is contraindicated in children under 12 due to dystonic reactions.

Formulation & Access

Brand Names

Stemetil, Stemzine

Oral Routes

Tablets (5 mg). Buccal tablets (3 mg - Stemzine).

Parenteral

Ampoules (12.5 mg/1 mL) for IM use. Suppositories for PR use.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Nausea and vomiting, vertigo, Meniere's disease.

Clinical Place

First-line agent for vestibular/inner-ear causes of nausea. Less effective for chemotherapy or gut-related nausea than Ondansetron.

Quick reference

Class & Role

D2 Antagonist — Phenothiazine antiemetic and antipsychotic.

Route / Formulation

Tablets (5 mg). Buccal tablets (3 mg - Stemzine). (Stemetil, Stemzine)

Usual Dose & Max

PO 5-10 mg TDS or QID (Max 20 mg/day).

Key Indication Doses

Nausea / Vertigo: PO 5-10 mg TDS or QID (Max 20 mg/day). Severe Acute Vertigo: IM 12.5 mg STAT (Deep IM injection only). Elderly / Frail: Start at PO 5 mg BD due to intense sedation and orthostatic hypotension risks.

Best Uses

Key Risks

Neurological: Acute dystonia, akathisia, tardive dyskinesia (with prolonged use). HIGH — Sedation, lethargy. Cardiovascular: Orthostatic hypotension (due to alpha-1 blockade). Gastrointestinal: Dry mouth, constipation (anticholinergic effect).

Key Interactions

Other D2 antagonists (Haloperidol, Metoclopramide) vastly increase risk of Neuroleptic Malignant Syndrome (NMS) and severe EPSE. Additive sedation with Opioids/Benzodiazepines.

Monitoring

Monitor BP for postural drops. If a young patient develops a stiff neck or locked jaw, give IV Benzatropine immediately (acute dystonia).

Clinical Pearl

Stemzine (buccal tablet) is placed high up between the upper lip and gum. It absorbs directly into the bloodstream, bypassing the liver. This makes a tiny 3mg buccal dose as effective as a 10mg swallowed tablet, and perfect for vomiting patients.

Access

Stemetil, Stemzine5 mg tablet

Brand: Stemetil, Stemzine
Formulation: Tablets (5 mg). Buccal tablets (3 mg - Stemzine).

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