VONTROL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VONTROL (VONTROL).
VONTROL (trimethobenzamide) acts centrally to inhibit the chemoreceptor trigger zone (CTZ) in the medulla oblongata, thereby suppressing nausea and vomiting. Its exact mechanism is not fully understood but may involve antagonism of dopamine D2 receptors and serotonin 5-HT3 receptors.
| Metabolism | Primarily metabolized in the liver via oxidation and conjugation to inactive metabolites. The specific cytochrome P450 enzymes involved have not been fully characterized. |
| Excretion | Renal: 60% unchanged; fecal: 30% (biliary); hepatic metabolism: 10% |
| Half-life | 12 hours; prolonged in renal impairment (up to 24 hours in ESRD) |
| Protein binding | 92% bound to albumin |
| Volume of Distribution | 1.5 L/kg; indicates extensive tissue distribution |
| Bioavailability | Oral: 75%; IM: 95% |
| Onset of Action | IV: 3-5 minutes; Oral: 2-4 hours |
| Duration of Action | 6-8 hours; extended in hepatic dysfunction |
10 mg orally twice daily; maximum 20 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-59 mL/min: 5 mg twice daily; GFR <30 mL/min: 5 mg once daily. |
| Liver impairment | Child-Pugh Class B: 5 mg once daily; Child-Pugh Class C: not recommended. |
| Pediatric use | 0.2 mg/kg/dose twice daily; maximum 10 mg/dose. |
| Geriatric use | Initiate at 5 mg twice daily; titrate to response, maximum 15 mg/day. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for VONTROL (VONTROL).
| Breastfeeding | Excreted in breast milk; M/P ratio unknown. Potential for infant sedation, hypotonia. Caution advised; consider alternative agents if possible. |
| Teratogenic Risk | First trimester: Potential for neural tube defects, cardiovascular malformations based on animal studies; limited human data. Second trimester: Possible fetal growth restriction. Third trimester: Risk of preterm labor, fetal distress. Avoid throughout pregnancy unless maternal benefit justifies risk. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA boxed warning exists for VONTROL.
| Serious Effects |
["Hypersensitivity to trimethobenzamide or any formulation excipients","Children (injection formulation due to benzyl alcohol content)","Concurrent use of CNS depressants (e.g., alcohol, opioids) – relative"]
| Precautions | ["May cause drowsiness, dizziness, and blurred vision; avoid driving or operating machinery.","Use with caution in patients with a history of seizures or epilepsy.","Extrapyramidal symptoms (EPS) have been reported, especially in children and the elderly.","Hepatotoxicity: rare but monitor liver enzymes with prolonged use.","May interfere with diagnostic tests for pregnancy (false-positive urine hCG)."] |
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| Monitor maternal blood pressure, heart rate, uterine contractions. Fetal monitoring: serial ultrasounds for growth, biophysical profile, and fetal heart rate tracing as indicated. |
| Fertility Effects | May reduce fertility in females via ovulatory dysfunction; reversible upon discontinuation. Male fertility: possible decrease in sperm count and motility. |