trimethobenzamide (Rx)

Frequency Not Defined

Dizziness

Parkinson-like symptoms

Sedation

Headache

Hypersensitivity reactions

Irritation at injection site

Contraindications

Hypersensitivity to drug or excipients

Cautions

EPS and other CNS symptoms, which can occur in patients treated with may be confused with CNS signs of undiagnosed primary disease (eg, encephalopathy, metabolic imbalance, Reye’s syndrome); if CNS symptoms occur, evaluate risks and benefits of continuing therapy

Serious CNS adverse reactions such as coma, depression of mood, disorientation, and seizures reported; recent use of other drugs that cause CNS depression or EPS symptoms (eg, alcohol, sedatives, hypnotics, opiates, anxiolytics, antipsychotics, and anticholinergics) may also increase risk for these serious CNS reactions; consider reducing daily dosage by increasing dosing interval or discontinuing drug

Therapy is potentially hepatotoxic; avoid use in patients whose signs and symptoms suggest presence of hepatic impairment; discontinue therapy in patients who develop impaired liver function while receiving drug

Therapy can cause drowsiness and may impair mental and/or physical abilities needed to perform hazardous tasks (driving a motor vehicle or operating machinery); choose therapy over concomitant use of other drugs that cause CNS depression or EPS symptoms (eg, alcohol, sedatives, hypnotics, opiates, anxiolytics, antipsychotics, and anticholinergics), depending on importance of drug to patient

Inform patients not to operate motor vehicles or other dangerous machinery until they are reasonably certain that therapy does not affect them adversely

Extrapyramidal symptoms

• Extrapyramidal symptoms (EPS), manifested primarily as acute dystonic reactions, may occur; dystonic reactions may include sudden onset of muscular spasms, especially in the head and neck or opisthotonos
• Other EPS include laryngospasm, dysphagia, and oculogyric crisis; involuntary spasms of tongue and mouth may lead to difficulty in speaking and swallowing; anticholinergic drugs can be used to treat acute dystonic reactions
• EPS may include akathisia, restlessness, akinesia, and other parkinsonian-like symptoms (eg, tremor); depending on severity of symptoms, reduce daily dosage by increasing dosing interval or discontinue therapy
• Avoid using drug in patients receiving other drugs that are likely to cause EPS (eg, antipsychotics)

Pregnancy

Limited available data in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage

Animal data

• No adverse developmental effect observed in animal reproduction studies with administration of therapy during organogenesis in pregnant rats at doses 0.16 and 0.8 times the recommended human dose (RHD) and in pregnant rabbits at doses 1.6 times the RHD

Lactation

There is no information on presence of drug in human milk, effects of drug on breastfed infant or on milk production; lack of clinical data during lactation precludes clear determination of risk of drug to infant during lactation

Consider developmental and health benefits of breastfeeding along with mother's clinical need for therapy and any potential adverse effects on breastfed infant from drug or from underlying maternal condition

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Unclear, the drug appears to directly affect medullary chemoreceptor trigger zone by inhibiting emetic stimuli to the vomiting center

Pharmacokinetics

Onset: 15-35 min (IM), 10-40 min (PO)

Duration: 2-3 hr (IM), 3-4 hr (PO)

Bioavailability: BA of oral dose equals 60-100% of IM dose

Half-life elimination: 7-9hr

Metabolism: Liver

Metabolites: N-desmethyl & N-oxide derivatives

Excretion: Urine (30-50%), feces via bile