Brand name: Soma
Drug class: Centrally Acting Skeletal Muscle Relaxants
VA class: MS200
CAS number: 78-44-4

Medically reviewed by Drugs.com on Feb 14, 2024. Written by ASHP.

Introduction

Skeletal muscle relaxant; structurally and pharmacologically related to meprobamate.^{100 a}

Uses for Carisoprodol

Muscular Conditions

Short-term (i.e., up to 2–3 weeks) relief of discomfort associated with acute, painful musculoskeletal conditions.^{29 100 101 102} Indicated for short-term use only;¹⁰⁰ prolonged use not adequately studied and may increase risk of abuse, dependence, and tolerance.^{100 113 114 117}

If pharmacologic therapy is required for acute low back pain (usually a benign and self-limiting condition^{105 106 108} ), experts state that an NSAIA or skeletal muscle relaxant may be considered.²⁰⁹ Skeletal muscle relaxants may provide small improvements in pain relief, but are associated with a high incidence of adverse effects (e.g., CNS effects).^{104 106 107 108 209} Use with caution after weighing risks against benefits.^{104 106 107 108}

Various skeletal muscle relaxants appear to have comparable efficacy for low back pain relief.^{103 104 106 108}

Carisoprodol is ineffective for treatment of skeletal muscle hyperactivity secondary to chronic neurologic disorders (e.g., cerebral palsy) and other dyskinesias.^{25 29}

Related/similar drugs

cyclobenzaprine, methocarbamol, baclofen, tizanidine, diazepam, Soma

Carisoprodol Dosage and Administration

Administration

Administer orally with or without food.¹⁰⁰

Dosage

Adults

Muscular Conditions

Oral

250–350 mg 3 times daily and at bedtime.¹⁰⁰

Prescribing Limits

Adults

Muscular Conditions

Oral

Do not administer for more than 2–3 weeks.¹⁰⁰

Cautions for Carisoprodol

Contraindications

• History of acute intermittent porphyria.¹⁰⁰

• Known hypersensitivity to carisoprodol or other carbamate derivatives (e.g., meprobamate).¹⁰⁰

Warnings/Precautions

Sensitivity Reactions

Hypersensitivity Associated with Meprobamate

Allergic or idiosyncratic reactions have been reported in patients receiving meprobamate, a metabolite of carisoprodol.¹⁰⁹

Reactions may be mild (e.g., pruritus, urticaria, erythematous maculopapular rash) or more severe (e.g., hyperpyrexia, chills, angioedema, bronchospasm, anaphylaxis, stomatitis, proctitis, oliguria, anuria, exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, bullous dermatitis).¹⁰⁹ Leukopenia, acute nonthrombocytopenic purpura, petechiae, ecchymoses, eosinophilia, adenopathy, peripheral edema, fever, and fixed drug eruptions with cross-reaction to carisoprodol also reported.¹⁰⁹

General Precautions

CNS Effects

Possible drowsiness and dizziness.¹⁰⁰ Vertigo, ataxia, tremor, agitation, irritability, headache, depressive reaction, syncope, and insomnia also reported.¹⁰⁰

Seizures have been reported, mostly in setting of multiple-drug overdoses (including drugs of abuse, illicit drugs, and alcohol).¹⁰⁰

Performance of activities requiring mental alertness or physical coordination may be impaired.¹⁰⁰ Carisoprodol use has been associated with motor vehicle accidents.^{100 114}

Concurrent use of other CNS depressants may potentiate CNS effects.^{100 122} (See Specific Drugs under Interactions.)

Abuse, Dependence, and Withdrawal

Subject to control as a schedule IV drug.¹⁰⁰ Potential for abuse, misuse, and diversion.^{100 108 113 114 117 118} Risk of abuse is greater with prolonged use and also in patients with a history of drug abuse or receiving other drugs with abuse potential (e.g., opiate analgesics, benzodiazepines, illicit drugs).^{100 108 112 114 115 118}

Both carisoprodol and its main active metabolite (meprobamate) may contribute to abuse potential.^{100 106 112 113 114 117 118 119}

Tolerance and physical dependence can occur with prolonged use.¹⁰⁰ Withdrawal symptoms (e.g., hallucinations, tremors, anxiety, muscle twitching, insomnia) reported following abrupt cessation of therapy after prolonged use.^{100 113 117} Instruct patients receiving large doses or prolonged therapy to not abruptly discontinue the drug.¹⁰⁰

Assess abuse potential prior to use.¹⁰⁰ Take special precautions during treatment to reduce risk of abuse (e.g., limit use to short periods of ≤3 weeks, maintain careful prescription records, monitor for signs of abuse and overdosage, educate patients and family members on abuse and proper storage and disposal of the drug).¹⁰⁰

GI Effects

Nausea, vomiting, and epigastric distress have been reported.^{100 a}

Cardiovascular Effects

Tachycardia, postural hypotension, and facial flushing have been reported.^{100 a}

Fixed Combinations

When used in fixed combination with aspirin and/or codeine, consider the cautions, precautions, and contraindications associated with the other agent(s).^{123 124}

Specific Populations

Pregnancy

No evidence of drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes with use of carisoprodol or meprobamate (an active metabolite) during pregnancy.¹⁰⁰ In animal reproductive studies, reduced fetal weights, postnatal weight gain, and postnatal survival observed.¹⁰⁰

Lactation

Distributed into milk; may reach concentrations that are 2–4 times maternal plasma concentrations.^{100 110 125} Not known whether the drug affects milk production.¹⁰⁰ Consider known benefits of breastfeeding along with mother's clinical need for carisoprodol and any potential adverse effects on the nursing infant from the drug or underlying maternal condition.¹⁰⁰ Monitor nursing infant for signs of sedation during breastfeeding.¹⁰⁰

Pediatric Use

Safety and efficacy not established in children <16 years of age.¹⁰⁰

Geriatric Use

Safety and efficacy not established in geriatric patients >65 years of age.¹⁰⁰

Because of risk of injury, skeletal muscle relaxants should generally be avoided in geriatric patients.¹¹¹

Hepatic Impairment

Use with caution; metabolized by the liver.^{100 a}

Renal Impairment

Use with caution; excreted by the kidneys.^{100 a}

Pharmacogenomics and Effects of CYP2C19 Polymorphism

Use with caution in patients with reduced CYP2C19 activity (i.e., poor metabolizers); potential for increased exposure to carisoprodol.^{100 120} (See Absorption: Special Populations, under Pharmacokinetics.)

Common Adverse Effects

Drowsiness, dizziness, headache.¹⁰⁰

Drug Interactions

Metabolized by CYP2C19.¹⁰⁰

Drugs Affecting Hepatic Microsomal Enzymes

CYP2C19 inhibitors: Potential pharmacokinetic interaction (increased exposure to carisoprodol and decreased exposure to meprobamate).¹⁰⁰ Clinical importance unknown.¹⁰⁰

CYP2C19 inducers: Potential pharmacokinetic interaction (decreased exposure to carisoprodol and increased exposure to meprobamate).¹⁰⁰ Clinical importance unknown.¹⁰⁰

Specific Drugs

Carisoprodol Pharmacokinetics

Absorption

Bioavailability

Peak plasma concentrations achieved in approximately 1.5–2 hours.^{100 121}

Food

High-fat meal does not affect pharmacokinetics.¹⁰⁰

Onset

Usually within 30 minutes.^a

Duration

4–6 hours.^a

Special Populations

Patients who are poor metabolizers of CYP2C19 may have fourfold increase in carisoprodol exposure and 50% decrease in meprobamate exposure compared with individuals with normal CYP2C19 function.¹⁰⁰ (See Pharmacogenomics and Effects of CYP2C19 Polymorphism under Cautions.)

Distribution

Extent

Crosses the placenta; distributes into milk in concentrations 2–4 times higher than concurrent maternal plasma concentrations.^{100 110 125}

Elimination

Metabolism

Metabolized in the liver by CYP2C19.^{100 112}

Several metabolites (meprobamate, hydroxycarisoprodol, hydroxymeprobamate) identified; meprobamate is main active metabolite.^{100 112 117}

Elimination Route

Eliminated via both renal and nonrenal routes.¹⁰⁰

Half-life

Carisoprodol: About 2 hours.^{100 121}

Meprobamate: About 10 hours.^{100 121}

Special Populations

May be removed by hemodialysis or peritoneal dialysis.¹⁰⁰ Accumulation of carisoprodol may occur in patients with hepatic or renal impairment.¹⁰⁰

Stability

Storage

Oral

Tablets

20–25°C in tight containers.¹⁰⁰

Fixed-combination preparation with aspirin and codeine: Tight, light-resistant containers at 20–25°C; protect from moisture.¹²³

Fixed-combination preparation with aspirin: Tight, light-resistant containers at 20–25°C; protect from moisture.¹²⁴

Actions

• CNS depressant with sedative and skeletal muscle relaxant effects.^{100 a}

• Precise mechanism of action not known; minimal skeletal muscle relaxant effects probably are related to sedation.^{100 a}

• No direct skeletal muscle relaxant effect;^{100 a} does not depress neuronal conduction, neuromuscular transmission, or muscle excitability.^a

• In animals, blocks interneuronal activity in descending reticular formation and spinal cord.¹⁰⁰

• May modify central perception of pain without abolishing peripheral pain reflexes and may have slight antipyretic activity.^{25 27}

Advice to Patients

• Potential for drug to cause drowsiness or dizziness and to impair mental alertness or physical coordination; use caution when driving or operating machinery until effects on individual are known.¹⁰⁰

• Potential for additive CNS depression if alcohol, benzodiazepines, opiate agonists, tricyclic antidepressants, sedating antihistamines, or other sedatives are used concomitantly.¹⁰⁰ Importance of avoiding alcohol during therapy.¹⁰⁰

• Risk of possible dependence, withdrawal, and abuse with prolonged therapy.¹⁰⁰

• Importance of limiting use to short term (up to 2–3 weeks).¹⁰⁰

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.¹⁰⁰

• Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.¹⁰⁰

• Importance of informing patients of other important precautionary information.¹⁰⁰ (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Carisoprodol is subject to control under the Federal Controlled Substances Act of 1970 as a schedule IV (C-IV) drug.¹⁰⁰ Preparations containing the drug combined with codeine phosphate are subject to control as schedule III (C-III) drugs.¹²³

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Frequently asked questions

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