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Vomet is contraindicated in patients with known hypersensitivity to trimethobenzamide.
The following adverse reactions from voluntary reports or clinical studies have been reported with trimethobenzamide. Because many of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Vomet is indicated in adults for the treatment of postoperative nausea and vomiting and for nausea associated with gastroenteritis.
Limitation Of UseVomet is not recommended for use in pediatric patients due to the risk of extrapyramidal signs and symptoms and other serious central nervous system (CNS) effects, and the risk of exacerbation of the underlying disease in pediatric patients with Reye’s syndrome or other hepatic impairment.
The pharmacokinetics of trimethobenzamide in healthy adult subjects were compared when Vomet was administered as a 300 mg oral capsule or a 200 mg (100 mg/mL) intramuscular injection. The time to reach maximum plasma concentration (Tmax) was about 30 minutes after intramuscular injection compared to about 45 minutes after oral capsule administration. The plasma concentration-time profile of trimethobenzamide was similar between the two formulations.
EliminationThe mean elimination half-life of trimethobenzamide is 7 to 9 hours.
Metabolism
The major pathway of trimethobenzamide metabolism is through oxidation resulting in the formation of trimethobenzamide N-oxide metabolite. The pharmacologic activity of this major metabolite has not been evaluated.
Excretion
Between 30 to 50% of a single dose in humans is excreted unchanged in the urine within 48 to 72 hours.
Included as part of the "PRECAUTIONS" Section
PRECAUTIONS Acute Dystonic Reactions And Other Extrapyramidal Symptoms (EPS)Extrapyramidal symptoms (EPS), manifested primarily as acute dystonic reactions, may occur with Vomet. 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 the tongue and mouth may lead to difficulty in speaking and swallowing. Anticholinergic drugs can be used to treat acute dystonic reactions.
EPS may also include akathisia, restlessness, akinesia, and other parkinsonian-like symptoms (e.g., tremor). Depending on the severity of symptoms, reduce the daily dosage of Vomet by increasing the dosing interval or discontinue Vomet.
Avoid Vomet in patients receiving other drugs that are likely to cause EPS (e.g. antipsychotics).
Masking Of Other Serious DisordersEPS and other CNS symptoms which can occur in patients treated with Vomet may be confused with CNS signs of undiagnosed primary disease (e.g., encephalopathy, metabolic imbalance, Reye’s syndrome)). If CNS symptoms occur, evaluate the risks and benefits of continuing Vomet for each patient.
Other CNS ReactionsOther serious CNS adverse reactions such as coma, depression of mood, disorientation, and seizures have been reported with Vomet administration. The recent use of other drugs that cause CNS depression or EPS symptoms (e.g., alcohol, sedatives, hypnotics, opiates, anxiolytics, antipsychotics, and anticholinergics) may also increase the risk for these serious CNS reactions. Consider reducing the daily dosage of Vomet by increasing the dosing interval or discontinuing the drug.
HepatotoxicityVomet is potentially hepatotoxic. Avoid use of Vomet in patients whose signs and symptoms suggest the presence of hepatic impairment. Discontinue Vomet in patients who develop impaired liver function while taking Vomet.
Effects On The Ability To Drive Or Operate MachineryVomet can cause drowsiness and may impair the mental and/or physical abilities required for the performance of hazardous tasks such as driving a motor vehicle or operating machinery. Concomitant use of other drugs that cause CNS depression or EPS symptoms (e.g., alcohol, sedatives, hypnotics, opiates, anxiolytics, antipsychotics, and anticholinergics) may increase this effect. Either Vomet or the other interacting drug should be chosen, depending on the importance of the drug to the patient. Inform patients not to operate motor vehicles or other dangerous machinery until they are reasonably certain that Vomet does not affect them adversely.
Use In Specific Populations Pregnancy Risk SummaryThe limited available data with trimethobenzamide in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage. No adverse developmental effect was observed in animal reproduction studies with administration of trimethobenzamide hydrochloride 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.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively.
DataAnimal Data
Reproduction studies with trimethobenzamide hydrochloride were conducted in rats and rabbits following administration of trimethobenzamide hydrochloride during organogenesis and no adverse developmental effect was observed in either species. The only effects observed were an increased percentage of embryonic resorptions or stillborn pups in rats administered 20 mg/kg and 100 mg/kg (0.16 and 0.8 times the RHD of 1200 mg/day, based on body surface area) and increased resorptions in rabbits receiving 100 mg/kg (1.6 times the RHD of 1200 mg/day, based on body surface area). In each study, these adverse effects were attributed to one or two dams.
Lactation Risk SummaryThere is no information on the presence of trimethobenzamide in human milk, the effects of Vomet on the breastfed infant or the effects of Vomet on milk production. The lack of clinical data during lactation precludes a clear determination of the risk of Vomet to an infant during lactation; therefore, the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for Vomet and any potential adverse effects on the breastfed infant from Vomet or from the underlying maternal condition.
Pediatric UseThe safety and effectiveness of Vomet in pediatric patients has not been established.
Vomet is not recommended for use in pediatric patients due to the risk of EPS and other serious CNS effects, and the risk of exacerbation of underlying disease in pediatric patients with Reye’s Syndrome, or other hepatic impairment.
Geriatric UseClinical studies of trimethobenzamide did not include sufficient numbers of patients aged 65 years and over to determine whether they respond differently from younger patients. Although there are studies reported in the literature that included geriatric patients 65 years and older with younger patients, it is not known if there are differences in efficacy or safety parameters for geriatric and non-geriatric patients treated with Vomet. Trimethobenzamide is excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. Because geriatric patients are more likely to have decreased renal function, reduce the daily dosage of Vomet by increasing the dosing interval and adjust as needed based upon therapeutic response and tolerability. Monitor renal function.
Renal ImpairmentTrimethobenzamide is eliminated by renal excretion. In patients with renal impairment (creatinine clearance 70 mL/min/1.73m2 or less), reduce the daily dosage by increasing the dosing interval and adjust as needed based upon therapeutic response and tolerability. Monitor renal function.
Hepatic ImpairmentAvoid Vomet in patients whose signs and symptoms suggest the presence of hepatic impairment due to the risk of hepatotoxicity. Discontinue Vomet in patients who develop impaired liver function while taking Vomet.
The recommended adult dosage is 300 mg orally three or four times daily. Select the lowest effective daily dosage and adjust as needed based upon therapeutic response and tolerability.
Dosage Adjustment For Geriatric Patients And/Or Patients With Renal ImpairmentIn geriatric patients and/or in patients with renal impairment (creatinine clearance 70 mL/min/1.73m2 or less), reduce the daily dosage of Vomet by increasing the dosing interval and adjust as needed based upon therapeutic response and tolerability. Monitor renal function.
300 mg trimethobenzamide hydrochloride; the capsule has an opaque purple cap marked “Vomet” and an opaque purple body marked “M079”.
