Introduction
Soma (carisoprodol) is a centrally-acting skeletal muscle relaxant approved by the FDA for the relief of discomfort associated with acute, painful musculoskeletal conditions. It is typically used as an adjunct to rest, physical therapy, and other measures for short-term management (2-3 weeks) due to its potential for abuse, dependence, and withdrawal.
Mechanism of Action
Carisoprodol's exact mechanism of action is not fully understood. It is believed to modify central nervous system communication, potentially through interruption of neuronal communication within the reticular formation and spinal cord. The drug undergoes rapid metabolism to meprobamate, which has anxiolytic and sedative properties and may contribute to its overall effects.
Indications
- FDA-approved: Short-term (2-3 weeks) adjunctive treatment of acute, painful musculoskeletal conditions
- Used in combination with rest, physical therapy, and other supportive measures
Dosage and Administration
Adults: 250-350 mg three times daily and at bedtime Maximum duration: 2-3 weeks Administration: Oral administration with or without food Special populations:- Geriatric: Use with caution due to increased sedation risk
- Hepatic impairment: Use contraindicated
- Renal impairment: Use with caution
- Pediatrics: Safety and effectiveness not established
Pharmacokinetics
Absorption: Rapidly absorbed from GI tract; peak plasma concentrations within 1.5-2 hours Distribution: Widely distributed throughout body; protein binding approximately 60% Metabolism: Extensive hepatic metabolism via CYP2C19 to active metabolite meprobamate Elimination: Half-life of carisoprodol is approximately 2 hours; meprobamate half-life is 10 hours Excretion: Primarily renal (renal clearance of meprobamate is reduced in elderly patients)Contraindications
- Acute intermittent porphyria
- History of allergic reaction to carisoprodol, meprobamate, or related compounds (meprobamate, tybamate, mebutamate)
- Severe hepatic impairment
Warnings and Precautions
Boxed Warning:- May be habit-forming; potential for abuse, dependence, and withdrawal
- Should only be used for short periods (2-3 weeks)
- Sedation may impair mental and physical abilities required for potentially hazardous tasks
- Seizures may occur following abrupt discontinuation after prolonged use
- Use caution in patients with history of drug abuse
- Increased risk of CNS depression when used with other CNS depressants
- Use caution in patients with compromised respiratory function
Drug Interactions
Major interactions:- Other CNS depressants (alcohol, benzodiazepines, opioids, sedatives): Additive CNS depression
- CYP2C19 inhibitors (omeprazole, fluvoxamine): May increase carisoprodol levels
- CYP2C19 inducers (rifampin): May decrease carisoprodol levels
- Meprobamate substrates: Potential for additive effects
Adverse Effects
Common (≥1%):- Drowsiness
- Dizziness
- Headache
- Nausea
- Vomiting
- Anaphylaxis
- Angioedema
- Seizures
- Tachycardia
- Orthostatic hypotension
- Dependence and withdrawal syndrome
- Psychological dependence
Monitoring Parameters
- Efficacy: Pain relief, muscle spasm reduction
- Safety: Sedation level, cognitive function
- Signs of abuse or dependence
- Withdrawal symptoms upon discontinuation
- Hepatic function (baseline and periodic)
- Renal function in patients with impairment
Patient Education
- Take exactly as prescribed; do not exceed recommended dose
- Avoid alcohol and other CNS depressants
- May cause drowsiness or dizziness; avoid driving or operating machinery until effects are known
- Do not stop abruptly after prolonged use due to withdrawal risk
- Store securely to prevent misuse by others
- Report any signs of allergic reaction or unusual side effects
- Use only for short-term treatment as directed
- Inform all healthcare providers about Soma use
References
1. FDA Prescribing Information: Soma (carisoprodol) tablets. Revised 2016. 2. Bramness JG, et al. Carisoprodol use and abuse. Drug Alcohol Depend. 2007;90(2-3):285-294. 3. Reeves RR, et al. Carisoprodol: update on abuse potential and legal status. South Med J. 2012;105(11):619-623. 4. Witenko C, et al. Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. P T. 2014;39(6):427-435. 5. Chou R, et al. Medications for acute and chronic low back pain: a review of the evidence for an American Pain Society/American College of Physicians clinical practice guideline. Ann Intern Med. 2007;147(7):505-514. 6. Micromedex Solutions: Carisoprodol. Truven Health Analytics. Accessed 2023. 7. American Geriatrics Society 2019 Updated AGS Beers Criteria® for Potentially Inappropriate Medication Use in Older Adults. J Am Geriatr Soc. 2019;67(4):674-694.