Generic Name: Carisoprodol
Class: Centrally Acting Skeletal Muscle Relaxants
VA Class: MS200
CAS Number: 78-44-4

Introduction

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

Uses for Soma

Muscular Conditions

Short-term (i.e., up to 2–3 weeks) relief of discomfort associated with acute, painful musculoskeletal conditions.^{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}

Slideshow: 10 Things to Know About Antibiotic Resistance

If pharmacologic therapy is required for acute low back pain (usually a benign and self-limiting condition^{105 106 108} ), an analgesic (i.e., acetaminophen, NSAIA) generally is recommended.^{104 105 106 108 117} Skeletal muscle relaxants may be used alone or in combination with analgesics for short-term relief; however, consider high incidence of adverse effects (e.g., CNS effects).^{104 106 107 108} Use skeletal muscle relaxants with caution and weigh 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.^a

Soma 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 Soma

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 mebrobamate, 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

Sulfite Sensitivity

Some formulations (e.g., Soma Compound with Codeine) contain sulfites, which may cause allergic-type reactions (including anaphylaxis and life-threatening or less severe asthmatic episodes) in certain susceptible individuals.^{126 127 128 129 130 131 132 133}

General Precautions

CNS Effects

Possible drowsiness and dizziness.^{100 a} 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

Abuse, tolerance, and dependence have been reported with prolonged use,^{100 108 113 114 117 118} mostly in patients with a history of addiction or who also were 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}

Withdrawal symptoms (e.g., hallucinations, tremors, anxiety, muscle twitching, insomnia) have been reported following abrupt cessation of therapy after prolonged use.^{100 113 117}

Use with caution in patients prone to addiction and in those receiving other CNS depressants (including alcohol).^{100 108 112 117} Limit duration of use to 2–3 weeks.^{100 117}

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

Category C.¹⁰⁰

Lactation

Distributed into milk; may reach concentrations that are 2–4 times maternal plasma concentrations.^{100 110 125} Use with caution; monitor infant closely for sedation or other changes in behavior or function.^{100 125}

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

Hepatic Impairment

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

Renal Impairment

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

Reduced CYP2C19 Activity

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

Interactions for Soma

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

Drug	Interaction	Comments
Alcohol	Potential additive CNS depression 100	Avoid concomitant use100
Aspirin	Possible decreased exposure to carisoprodol and increased exposure to meprobamate100	Clinical importance unknown100
CNS depressants (e.g., benzodiazepines, opiate agonists, tricyclic antidepressants)	Potential additive CNS depression 100 122	Use concomitantly with caution100 122
Fluvoxamine	Possible increased exposure to carisoprodol and decreased exposure to meprobamate100	Clinical importance unknown100
Meprobamate	Additive pharmacologic effects since meprobamate is active metabolite of carisoprodol100	Avoid concomitant use100
Omeprazole	Possible increased exposure to carisoprodol and decreased exposure to meprobamate100	Clinical importance unknown100
Rifampin	Possible decreased exposure to carisoprodol and increased exposure to meprobamate100	Clinical importance unknown100
St. John's wort (Hypericum perforatum)	Possible decreased exposure to carisoprodol and increased exposure to meprobamate100	Clinical importance unknown100

Soma 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 with genetic CYP2C19 deficiency (i.e., poor metabolizers) may have fourfold increase in carisoprodol exposure and 50% decrease in meprobamate exposure compared with individuals with normal CYP2C19 function.¹⁰⁰

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.¹⁰⁰

Fixed-combination preparation with aspirin and codeine: Tight, light-resistant containers at 15–30°C; protect from moisture.¹²³

Fixed-combination preparation with aspirin: Tight 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.^a

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 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.

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

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

Carisoprodol

Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Oral	Tablets	250 mg	Carisoprodol Tablets (C-IV)
			Soma (C-IV)	Meda
		350 mg*	Carisoprodol Tablets (C-IV)
			Soma (C-IV)	Meda

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

Carisoprodol Combinations

Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Oral	Tablets	200 mg with Aspirin 325 mg*	Carisoprodol and Aspirin Tablets (C-IV)
			Soma Compound (C-IV)	Meda
		200 mg with Aspirin 325 mg and Codeine Phosphate 16 mg*	Carisoprodol, Aspirin and Codeine Phosphate Tablets (C-III)
			Soma Compound with Codeine (C-III)	Meda

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 02/2013. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.

Carisoprodol 350MG Tablets (QUALITEST): 30/$14.99 or 90/$35.97

Carisoprodol-Aspirin 200-325MG Tablets (SANDOZ): 30/$65.99 or 90/$169.96

Carisoprodol-Aspirin-Codeine 200-325-16MG Tablets (SANDOZ): 30/$82.99 or 90/$235.96

Soma 250MG Tablets (MEDA PHARMACEUTICALS): 100/$399.00 or 300/$1,155.94

Soma 350MG Tablets (MEDA PHARMACEUTICALS): 30/$205.99 or 90/$560.94

Soma Compound 200-325MG Tablets (MEDA PHARMACEUTICALS): 30/$139.99 or 90/$399.96