Carisoprodol: Mechanism and Renal Effects
Carisoprodol (Soma) is a centrally acting muscle relaxant with substantial barbiturate-like properties that should be used with caution in patients with renal dysfunction due to potential accumulation and increased risk of adverse effects.
What is Carisoprodol?
- Carisoprodol is a centrally acting muscle relaxant with anxiolytic properties, rapid onset of action, and effects lasting 4-6 hours 1
- It is commonly known by the brand name Soma and has substantial barbiturate-like biological action 1
- It is classified as a controlled substance due to its significant abuse and addiction potential 1
Mechanism of Action
- Acts as a central nervous system depressant with anxiolytic properties 1
- Metabolized to meprobamate, which is itself a Schedule IV controlled substance 2, 3
- Produces sedative effects that can impair psychomotor function even at therapeutic doses 4
Effects on Kidney Function
- The safety and pharmacokinetics of carisoprodol in patients with renal impairment have not been formally evaluated 5
- Caution should be exercised when administering carisoprodol to patients with impaired renal function since it is excreted by the kidney 5
- Carisoprodol is dialyzable by both hemodialysis and peritoneal dialysis 5
Clinical Considerations for Renal Patients
- Dose adjustments may be necessary for patients with impaired renal function, though specific guidelines are not available 5
- Patients with reduced CYP2C19 activity have higher exposure to carisoprodol and require additional caution 5
- Monitoring for adverse effects is particularly important in patients with kidney dysfunction 5
Adverse Effects and Risks
- Numerous adverse effects including sedation, seizures, drug dependence, withdrawal, tachycardia, and postural hypotension 1
- Even at therapeutic doses (350 mg), carisoprodol can produce psychomotor impairment while causing minimal subjective effects, creating risk for activities like driving 4
- With prolonged abuse at high dosages, carisoprodol can lead to tolerance, dependence, and withdrawal symptoms 1, 6
- Withdrawal can cause severe symptoms including insomnia, vomiting, tremors, muscle twitching, anxiety, ataxia, and potentially hallucinations and delusions 6
Clinical Recommendations
- If prescribed, carisoprodol usage should be limited to short-term treatment only 2
- The FDA has reported escalating abuse of carisoprodol in the past decade, making it one of the most commonly diverted drugs 1
- When discontinuing, carisoprodol should always be tapered slowly (over 4-9 days) rather than stopped abruptly to prevent withdrawal symptoms 1
- For perioperative management, it is recommended to hold carisoprodol on the day of operation and consider tapering off or switching to an alternative agent before surgical procedures 1
- A lower dose of 250 mg may provide similar efficacy to the standard 350 mg dose with fewer adverse events 7
Special Precautions
- Exercise particular caution in patients with a history of substance abuse, as they are at higher risk for abusing carisoprodol 3
- Patients prescribed carisoprodol are at risk for meprobamate dependence 2
- Many physicians may be unaware of carisoprodol's abuse potential and its metabolism to meprobamate 3