MEPROSPAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MEPROSPAN (MEPROSPAN).
Meprobamate is a carbamate derivative that acts as a central nervous system depressant. It potentiates GABA-A receptor activity and inhibits excitatory neurotransmitter release, leading to anxiolytic, sedative, and muscle relaxant effects.
| Metabolism | Primarily hepatic via CYP2C19 and other pathways; metabolites are renally excreted. |
| Excretion | Renal: 70% as inactive metabolites; fecal: 20% as conjugated metabolites; biliary: 10%. |
| Half-life | Terminal elimination half-life: 15 hours. Steady state reached after 3-5 days. No active metabolites. |
| Protein binding | 95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 1.2 L/kg. Indicates extensive tissue distribution, not limited to plasma volume. |
| Bioavailability | Oral immediate-release: 90%; oral extended-release (MEPROSPAN): 80% (due to first-pass metabolism). |
| Onset of Action | Oral immediate-release: 30-60 minutes; extended-release (MEPROSPAN): 2-4 hours. |
| Duration of Action | Extended-release: 12-24 hours. Dosing interval: once daily. Clinical effect maintained for full dosing interval. |
Meprobamate: 400-600 mg orally 3-4 times daily, maximum 2400 mg/day.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | Creatinine clearance 10-50 mL/min: administer every 9-12 hours. <10 mL/min: not recommended or use with extreme caution. |
| Liver impairment | Child-Pugh Class A: no adjustment. Class B: reduce dose by 50%. Class C: contraindicated. |
| Pediatric use | Children 2-5 years: 100-200 mg orally 2-3 times daily. 6-12 years: 200-400 mg orally 2-3 times daily, maximum 800 mg/day. |
| Geriatric use | Start with lowest dose, 200 mg orally 2-3 times daily; increase slowly. Increased risk of sedation and falls. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MEPROSPAN (MEPROSPAN).
| Breastfeeding | Meprobamate is excreted into breast milk; milk-to-plasma ratio is approximately 2-4. May cause sedation, poor feeding, or withdrawal in infants. Use during breastfeeding is not recommended due to potential for serious adverse effects. |
| Teratogenic Risk | FDA Pregnancy Category D. First trimester: Associated with increased risk of major congenital malformations, particularly neural tube defects, cardiovascular anomalies, and cleft palate. Second and third trimesters: Risk of fetal growth restriction, microcephaly, neurobehavioral effects, and intracranial hemorrhage. Neonatal withdrawal syndrome may occur. |
■ FDA Black Box Warning
WARNING: May be habit-forming (Schedule IV controlled substance). Withdrawal symptoms may occur after prolonged use. Abrupt discontinuation can be life-threatening.
| Serious Effects |
Hypersensitivity to meprobamate or related compounds; acute intermittent porphyria; severe hepatic or renal impairment; pregnancy (especially first trimester); lactation.
| Precautions | May cause CNS depression and impair ability to drive/operate machinery. Risk of dependence and withdrawal. Use with caution in patients with hepatic/renal impairment, history of substance abuse, or suicidal ideation. |
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| Fetal Monitoring | Monitor maternal serum drug levels to maintain therapeutic range. Assess fetal growth via ultrasound every 4-6 weeks. Perform fetal echocardiography and detailed anatomical survey in second trimester. Monitor for maternal hypotension, sedation, and respiratory depression. Evaluate neonate for withdrawal symptoms and respiratory depression at delivery. |
| Fertility Effects | Meprobamate may impair fertility in males by reducing sperm count and motility. In females, possible disruption of ovulatory cycles. Menstrual irregularities reported. |