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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
• 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.
CNS: drowsiness, dizziness, headache, depression, disorientation, parkinsonian symptoms, coma, seizures
EENT: blurred vision
Hematologic: blood dyscrasias
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
• 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.
• 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.
Time/action profile (antiemetic effect)
|PO||10–40 min||unknown||3–4 hr|
|IM||15–35 min||unknown||2–3 hr|
Adverse Reactions/Side Effects
Central nervous system
- coma (life-threatening)
- seizures (life-threatening)
- drowsiness (most frequent)
- extrapyramidal reactions
- hypotension (most frequent)
- blood dyscrasias
- pain (most frequent)
- burning at IM injection site
- redness at IM injection site
- stinging at IM injection site
Drug-Drug interaction↑ CNS depression with other CNS depressants, including alcohol, antidepressants, antihistamines, opioid analgesics, and sedative/hypnotics.
Renal Impairment(Adults) CCr ≤70 mL/min—↓ dose or ↑ dosing interval.
Availability (generic available)
- Assess patient for nausea and vomiting prior to and 30–60 min following administration.
- Assess BP for hypotension following parenteral administration.
Potential Nursing DiagnosesRisk for deficient fluid volume (Indications)
Risk for injury (Side Effects)
- Oral: Capsules can be opened and contents mixed with food or fluids for patients with difficulty swallowing.
- Intramuscular: Inject deep into well-developed muscle mass to minimize tissue irritation.
- Trimethobenzamide is not receommended for IV use.
- Instruct patient to take medication as directed. Take missed doses as soon as remembered unless almost time for next dose; do not double doses.
- Advise patient to make position changes slowly to minimize orthostatic hypotension following parenteral doses.
- May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.
- Caution patient to avoid taking alcohol or other CNS depressants concurrently with this medication.
- Instruct patient to notify health care professional promptly if sore throat, fever, unusual weakness or tiredness, tremors, or yellowing of the skin and eyes occurs.
- Prevention and relief of nausea and vomiting.