SOMA
Clinical safety rating
cautionComprehensive clinical and safety monograph for SOMA (SOMA).
Centrally acting muscle relaxant; acts at brainstem reticular formation and spinal cord levels to inhibit polysynaptic reflexes, possibly via GABAergic and monoaminergic pathways.
| Metabolism | Hepatic via CYP2C19 and CYP3A4; also undergoes dealkylation and hydroxylation. |
| Excretion | Renal: ~60-70% as metabolites (including meprobamate and glucuronide conjugates); fecal: minimal; biliary: negligible. |
| Half-life | 1-2 hours; prolonged to 3-4 hours in hepatic impairment; parent drug rapidly cleared via CYP2C19 metabolism to meprobamate (active, t1/2 6-16 hours). |
| Protein binding | ~60% bound to albumin. |
| Volume of Distribution | 0.7-1.0 L/kg; consistent with moderate tissue distribution. |
| Bioavailability | Oral: ~100% (rapidly and completely absorbed). |
| Onset of Action | Oral: 30 minutes; peak effect at 1-2 hours. |
| Duration of Action | 2-4 hours for sedative effect; muscle relaxant effects may persist up to 6 hours; repeated dosing leads to tolerance and shorter duration. |
| Molecular Weight | 260.34 |
250 mg to 350 mg orally three times daily and at bedtime.
| Dosage form | CAPSULE |
| Renal impairment | No specific dose adjustment guidelines; use with caution in severe renal impairment (GFR <30 mL/min). |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). Use with caution in mild to moderate impairment; reduce dose or extend dosing interval. |
| Pediatric use | Not recommended for children under 12 years of age. For adolescents, adult dosing may be considered based on weight and clinical judgment. |
| Geriatric use | Initiate at lower doses (e.g., 250 mg three times daily) due to increased sensitivity and risk of CNS adverse effects; monitor renal function. |
| 1st trimester | Avoid; associated with increased risk of congenital malformations, particularly cardiac defects and oral clefts, based on epidemiologic studies. |
| 2nd trimester | Avoid; use only if clearly needed and benefit outweighs risk, close monitoring. |
| 3rd trimester | Avoid; may cause neonatal withdrawal syndrome, respiratory depression, and hypotonia. |
Clinical note
Comprehensive clinical and safety monograph for SOMA (SOMA).
| Placental transfer | Crosses placenta (detected in cord blood and amniotic fluid); data from case reports and animal studies confirm transfer. |
| Breastfeeding | Excretion into human milk is minimal but theoretical risk of sedation and respiratory depression in infant; use caution, especially with large doses or prolonged use. |
| Lactation Rating | L3 |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Limited human data; animal studies show increased fetal resorptions and skeletal anomalies. Second/third trimester: Risk of neonatal withdrawal syndrome (irritability, hypertonia) with chronic maternal use near term. |
| Fetal Monitoring | Monitor maternal CNS depression, respiratory rate, and blood pressure. Assess fetal heart rate and uterine activity if used during labor. Neonatal observation for withdrawal symptoms if chronic maternal use. |
| Fertility Effects | No human data on fertility impairment. Animal studies have not demonstrated adverse effects on fertility. |
■ FDA Black Box Warning
None
| Serious Effects |
PorphyriaHypersensitivity to carisoprodol or meprobamateAcute intermittent porphyria
| Precautions | May cause sedation, dizziness, and impaired psychomotor function; avoid driving or operating machinery., Risk of abuse, dependence, and withdrawal; use with caution in patients with substance use disorder., Concomitant use with alcohol or other CNS depressants may potentiate effects., Elderly patients more sensitive to anticholinergic effects; monitor for confusion or falls., Hepatic impairment: reduce dose or avoid use., Pregnancy: limited data; use only if clearly needed. |
| Food/Dietary | No specific food interactions reported. Avoid alcohol and grapefruit juice as they may enhance sedative effects. |
| Clinical Pearls | SOMA (carisoprodol) is a centrally acting skeletal muscle relaxant metabolized to meprobamate, a controlled substance with abuse potential. Avoid in patients with porphyria. Use lowest effective dose for shortest duration (max 2-3 weeks). Monitor for sedation and dizziness, especially when combined with other CNS depressants. Taper to avoid withdrawal if used long-term. |
| Patient Advice | Avoid driving or operating machinery until you know how SOMA affects you, as it may cause drowsiness or dizziness. · Do not consume alcohol or other CNS depressants (e.g., benzodiazepines, opioids) while taking SOMA. · Take exactly as prescribed; do not increase dose or duration due to risk of dependence and withdrawal. · Store securely to prevent misuse; dispose of unused medication properly. · Contact your doctor if you experience severe drowsiness, confusion, or signs of allergic reaction. |
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