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trimethobenzamide

R06AA10

Forms & Strengths

Oral tablets 100 mg
Oral suspension 25 mg/5 mL
IV/IM solution 200 mg/5 mL

Adult Dosing

300 mg/day divided q6h (100 mg each dose)
Maximum 400 mg/day in severe cases
Injectable: 200 mg IM/IV every 6‑8 h as needed

Pediatric Dosing

0.5‑1 mg/kg per dose q6‑8 h (max 300 mg/day)
Oral suspension preferred; IV/IM only if unable to take orally
Use with caution in children <12 y; safety data limited

Indications

Nausea and vomiting of any etiology
Post‑operative nausea and vomiting
Chemotherapy‑induced nausea (adjunct)
Radiation‑induced nausea
Vertigo‑related vomiting

Mechanism of Action

Peripheral dopamine D2‑receptor antagonist
Blocks chemoreceptor trigger zone
Reduces gastric motility and secretions

Contraindications

Known hypersensitivity to trimethobenzamide
Severe hepatic or renal failure (use with caution)
Patients with Parkinson disease (may worsen symptoms)
Concurrent use of other potent dopamine antagonists

Adverse Reactions

Drowsiness, dizziness, headache
Dry mouth, constipation, blurred vision (anticholinergic)
Extrapyramidal symptoms (tremor, dystonia)
Orthostatic hypotension, syncope
QT prolongation, arrhythmias (rare)

Drug Interactions

Additive CNS depression with alcohol, opioids, benzodiazepines
Increased anticholinergic burden with antihistamines, tricyclics, antispasmodics
Enhanced extrapyramidal risk when combined with phenothiazines or haloperidol
CYP2D6 substrates may have altered levels (e.g., metoprolol)
Potential potentiation of antihypertensives leading to hypotension

Curated Content: Needs Vetting Before Put to Clinical Use