Trimethobenzamide

TIGAN

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What it isCentrally acting antiemetic, probably through chemoreceptor-trigger-zone dopamine antagonism; used in adults for postoperative nausea and vomiting and gastroenteritis-associated nausea.

Why this oneAn alternative when common antiemetics are ineffective or contraindicated, though evidence and use are limited.

What limits itDrowsiness and acute dystonic or other extrapyramidal reactions limit use; avoid pediatric use and reduce dosing when renal clearance is impaired.

FDA-approved for

nausea (~1959)

FDA label

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FDA dosing	Population	Start	Target	Max
Nausea and vomiting	Adults	300 mg TID–QID	300 mg TID–QID	1200 mg/day

Renal CrCl ≤70 mL/min/1.73m2: reduce daily dose by increasing the dosing interval; monitor renal function

Hepatic Avoid in suspected hepatic impairment (hepatotoxicity risk); discontinue if impaired liver function develops

Instructions

Oral; select the lowest effective daily dosage and adjust to response/tolerability

Cautions

Acute dystonic reactions/EPS — reduce dose or discontinue; avoid with other EPS-causing drugs
May mask CNS signs of undiagnosed disease (e.g., encephalopathy, Reye's syndrome)
Other serious CNS reactions: coma, mood depression, disorientation, seizures
Hepatotoxicity — avoid in hepatic impairment, discontinue if liver function worsens
Drowsiness — may impair driving/operating machinery

Adverse reactions

Parkinson-like symptoms
Drowsiness, dizziness, headache
Blurred vision
Diarrhea, muscle cramps
Jaundice
Blood dyscrasias
Hypersensitivity (angioedema, skin reactions)

Pregnancy Limited human data insufficient to assess risk; no adverse developmental effects in animal studies

Lactation No human data; weigh benefits of breastfeeding against maternal need

NO BOXED WARNINGS

Principal riskacute dystonia and other extrapyramidal reactions

Cost, est. cash$300–$5,000/dose or month

Generic entry1982

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability1 / 4

Sedation liability1 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryB

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.