trimethobenzamide hydrochloride

trimethobenzamide hydrochloride


Pharmacologic class: Anticholinergic

Therapeutic class: Antiemetic

Pregnancy risk category C


Unclear. Thought to block dopamine receptors and emetic impulses in chemoreceptor trigger zone, preventing nausea and vomiting.


Capsules: 300 mg

Injection: 100 mg/ml in 2-ml ampules and prefilled syringes and in 20-ml vials

Indications and dosages

Nausea and vomiting

Adults: 300 mg P.O. three to four times daily or 200 mg I.M. three to four times daily

Dosage adjustment

• Renal impairment


• Hypersensitivity to drug

• Parenteral form in children


Use cautiously in:

• renal impairment, arrhythmias, encephalitis, gastroenteritis, dehydration, electrolyte imbalances

• concurrent alcohol use

• elderly or debilitated patients

• pregnant or breastfeeding patients

• children with known or suspected viral illnesses.


• In I.M. use, inject deep into upper outer quadrant of gluteus maximus.

• Withhold drug in children with signs or symptoms of Reye's syndrome.

Adverse reactions

CNS: drowsiness, dizziness, headache, depression, disorientation, parkinsonian symptoms, coma, seizures

CV: hypotension

EENT: blurred vision

Hematologic: blood dyscrasias

Hepatic: jaundice

Musculoskeletal: muscle cramps, opisthotonos

Skin: rash, urticaria, flushing

Other: pain and stinging at I.M. injection site, hypersensitivity reaction


Drug-drug. Antidepressants, antihistamines, CNS depressants, opioids, sedative-hypnotics: additive CNS depression

Drug-behaviors. Alcohol use: additive CNS depression

Patient monitoring

• Monitor neurologic status, especially for parkinsonian symptoms and other serious adverse reactions.

• Assess CBC and liver function tests. Watch for blood dyscrasias and jaundice.

• Evaluate injection site for pain and stinging.

• Closely monitor patient's nutritional and hydration status. Report continuing nausea.

Patient teaching

• Advise patient to take as needed for nausea and vomiting, but only as prescribed.

• Tell patient to contact prescriber promptly if nausea persists despite therapy.

• Instruct patient to minimize nausea and vomiting by eating small, frequent servings of healthy food and drinking plenty of fluids.

• Advise patient to avoid alcohol.

• Caution patient to avoid driving and other hazardous activities until drug effects are known.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and behaviors mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved
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Tigan and other suppository drug products that contain trimethobenzamide hydrochloride have not been shown to be effective for nausea and vomiting and should no longer be marketed, according to the Food and Drug Administration.