Trimethobenzamide (Intramuscular)

Generic name:

Trimethobenzamide

Drug class:

Antiemetic; benzamide derivative; dopamine D2 receptor antagonist

Dosage form:

Intramuscular injection (200 mg/mL solution)

Root of administration:

Intramuscular

Dose:

Adults: 200 mg intramuscularly every 4–6 hours as needed, not to exceed 1200 mg per 24 hours. Pediatrics: Safety and efficacy not established for intramuscular use; consult label.

Mechanism of action:

Selective antagonism of dopamine D2 receptors in the chemoreceptor trigger zone and gastrointestinal tract, raising the threshold for emetic stimuli.

Drug usage cases:

• Prevention and treatment of nausea and vomiting due to surgery or anesthesia
• Gastroenteritis-induced vomiting
• Migraine-associated vomiting
• Vestibular disorders (motion-induced nausea)
• Off-label: chemotherapy-induced nausea and vomiting (CINV)
• Off-label: motion sickness

Drug contra indications:

• Hypersensitivity to trimethobenzamide or any component of the formulation
• Gastrointestinal obstruction
• History of extrapyramidal reactions to phenothiazines or other dopamine antagonists
• Parkinson’s disease
• Concurrent severe central nervous system depression (e.g., from alcohol or sedatives)
• Pediatrics: children under 2 years of age

Side effects:

• Central nervous system: drowsiness, dizziness, headache, fatigue, restlessness, extrapyramidal symptoms (acute dystonia, parkinsonism, akathisia, tardive dyskinesia)
• Gastrointestinal: diarrhea, constipation, dry mouth
• Cardiovascular: hypotension, hypertension, tachycardia, syncope
• Hematologic: agranulocytosis, leukopenia, thrombocytopenia
• Hypersensitivity: rash, urticaria, pruritus, angioedema, anaphylaxis
• Local: injection site pain, injection site rash
• Respiratory: bronchospasm (rare)

Warnings:

• Risk of extrapyramidal symptoms; monitor particularly in elderly and pediatric patients
• Tardive dyskinesia: may be irreversible; minimize duration of therapy
• Neuroleptic malignant syndrome: discontinue immediately if suspected
• May cause significant sedation; caution when driving or operating machinery
• Use with caution in severe hepatic or renal impairment
• Electrolyte imbalances and dehydration may increase adverse reaction risk
• Concomitant use with other central nervous system depressants may enhance sedation
• Monitor complete blood count during prolonged therapy

Use during pregnancy or breastfeeding:

Pregnancy Category C: animal studies have shown adverse fetal effects; use only if the potential benefit justifies the risk to the fetus. Excreted in breast milk; may cause sedation or other adverse effects in nursing infants; weigh benefits of therapy against potential risks and consider discontinuation of breastfeeding or the drug.