What is Soma (Carisoprodol)?
Soma (carisoprodol) is a centrally acting muscle relaxant with substantial barbiturate-like biological action that is now classified as a controlled substance due to significant abuse and addiction potential, and should generally be avoided in favor of safer alternatives. 1
Pharmacological Profile
Carisoprodol is a CNS depressant with anxiolytic properties, rapid onset of action, and effects lasting 4 to 6 hours. 1 The drug is metabolized to meprobamate, a Schedule IV controlled substance, which contributes to its abuse liability. 2, 3
- The FDA approves carisoprodol only for short-term use (2-3 weeks maximum) for relief of discomfort associated with acute, painful musculoskeletal conditions in adults. 4
- It is available as 350 mg round, white tablets and is present as a racemic mixture with the molecular formula C12H24N2O4. 4
Critical Safety Concerns
The FDA has reported that carisoprodol abuse has escalated in the past decade and is one of the most commonly diverted drugs in the United States. 1, 5
Adverse Effects Include:
- Sedation, seizures, drug dependence 1
- Tachycardia and postural hypotension 1
- Withdrawal symptoms that can be severe 1
Withdrawal Syndrome:
Withdrawal from carisoprodol can cause severe symptoms including insomnia, vomiting, tremors, muscle twitching, anxiety, ataxia, and potentially hallucinations and delusions. 5 The drug should always be tapered slowly over 4 to 9 days rather than stopped abruptly. 1
Comparative Efficacy
While carisoprodol demonstrated superiority over diazepam in head-to-head trials (70% vs. 45% rated "excellent" or "very good"), there is no evidence that it is more effective than non-benzodiazepine muscle relaxants such as cyclobenzaprine, methocarbamol, or metaxalone. 5
- Systematic reviews conclude that muscle relaxants as a class have similar efficacy profiles with no clear superiority of one agent over another. 5
- NSAIDs are equally effective as muscle relaxants for acute low back pain and have fewer adverse effects. 5
Clinical Recommendations
Perioperative Management:
The Society for Perioperative Assessment and Quality Improvement recommends holding carisoprodol on the day of operation, and if time permits, tapering off or switching to an alternative agent before surgical procedures. 1, 5
Preferred Alternatives:
Choose cyclobenzaprine, methocarbamol, or metaxalone over carisoprodol for acute musculoskeletal conditions, as these agents have similar efficacy without the controlled substance classification. 5
- For elderly patients requiring muscle relaxant therapy, baclofen is the preferred agent, starting at 5 mg three times daily with gradual titration. 5
- Tizanidine is another recommended option with emerging evidence for perioperative benefit, including improved postoperative pain control and decreased opioid consumption. 5
First-Line Therapy:
Consider NSAIDs or acetaminophen as first-line therapy before any muscle relaxant, given comparable efficacy and superior safety profiles. 5
Red Flags for Abuse
Suspicions of abuse should be raised by patients requesting the drug by name, "losing" prescriptions, using carisoprodol chronically, or denying the efficacy of less mind-altering alternatives. 6
- Patients with a history of substance abuse are at particularly high risk for carisoprodol abuse. 7
- A significant percentage of physicians remain unaware of carisoprodol's abuse potential and its metabolism to meprobamate. 7
Common Pitfall
Do not prescribe carisoprodol in the mistaken belief that it relieves muscle spasm—muscle relaxants' effects are nonspecific and not related to actual muscle relaxation. 1, 8 If muscle spasm is suspected, the underlying cause should be addressed rather than relying on this medication class.