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

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If pharmacologic therapy is required for acute low back pain (usually a benign and self-limiting condition105 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 02/2014. 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

AHFS DI Essentials. © Copyright, 2004-2014, Selected Revisions November 18, 2012. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.

References

100. Meda Pharmaceuticals Inc. Soma (carisoprodol) tablets prescribing information. Somerset, NJ; 2011 Dec.

101. Serfer GT, Wheeler WJ, Sacks HJ. Randomized, double-blind trial of carisoprodol 250 mg compared with placebo and carisoprodol 350 mg for the treatment of low back spasm. Curr Med Res Opin. 2010; 26:91-9. [PubMed 19908948]

102. Ralph L, Look M, Wheeler W et al. Double-blind, placebo-controlled trial of carisoprodol 250-mg tablets in the treatment of acute lower-back spasm. Curr Med Res Opin. 2008; 24:551-8. [PubMed 18194591]

103. See S, Ginzburg R. Skeletal muscle relaxants. Pharmacotherapy. 2008; 28:207-13. [PubMed 18225966]

104. van Tulder MW, Touray T, Furlan AD et al. Muscle relaxants for non-specific low back pain. Cochrane Database Syst Rev. 2003; :CD004252. [PubMed 12804507]

105. Roelofs PD, Deyo RA, Koes BW et al. Non-steroidal anti-inflammatory drugs for low back pain. Cochrane Database Syst Rev. 2008; :CD000396. [PubMed 18253976]

106. Chou R, Qaseem A, Snow V et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007; 147:478-91. [PubMed 17909209]

107. Institute for Clinical Systems Improvement. Health care guideline: adult acute and subacute low back pain 15th ed. Bloomington, MN; 2012 Jan. From the ICSI website

108. Toth PP, Urtis J. Commonly used muscle relaxant therapies for acute low back pain: a review of carisoprodol, cyclobenzaprine hydrochloride, and metaxalone. Clin Ther. 2004; 26:1355-67. [PubMed 15530999]

109. Watson Laboratories, Inc. Meprobamate tablets prescribing information. Corona, CA; 2004 Apr.

110. Nordeng H, Zahlsen K, Spigset O. Transfer of carisoprodol to breast milk. Ther Drug Monit. 2001; 23:298-300. [PubMed 11360042]

111. Briggs GG, Ambrose PJ, Nageotte MP et al. High-dose carisoprodol during pregnancy and lactation. Ann Pharmacother. 2008; 42:898-901. [PubMed 18460586]

112. Reeves RR, Beddingfield JJ, Mack JE. Carisoprodol withdrawal syndrome. Pharmacotherapy. 2004; 24:1804-6. [PubMed 15585447]

113. Reeves RR, Hammer JS, Pendarvis RO. Is the frequency of carisoprodol withdrawal syndrome increasing?. Pharmacotherapy. 2007; 27:1462-6. [PubMed 17896902]

114. Drug Enforcement Administration (DEA), Department of Justice. Schedules of controlled substances: placement of carisoprodol into schedule IV. 21 CFR Part 1308. Final Rule. [Docket No. DEA-333]. Fed Regist. 2011; 76: 77330-60.

115. Owens C, Pugmire B, Salness T et al. Abuse potential of carisprodol: a retrospective review of Idaho Medicaid pharmacy and medical claims data. Clin Ther. 2007; 29:2222-5. [PubMed 18042478]

116. Fass JA. Carisoprodol legal status and patterns of abuse. Ann Pharmacother. 2010; 44:1962-7. [PubMed 21062909]

117. Boothby LA, Doering PL, Hatton RC. Carisoprodol: a marginally effective skeletal muscle relaxant with serious abuse potential. Hosp Pharm. 2003; 38: 337-45.

118. US Department of Health and Human Services, Substance Abuse and Mental Health Services Administration (SAMHSA), Center for Behavioral Health Statistics and Quality. DAWN report: ED visits involving the muscle relaxant carisoprodol. 2011 Oct 27. From the SAMHSA website.

119. Gonzalez LA, Gatch MB, Taylor CM et al. Carisoprodol-mediated modulation of GABAA receptors: in vitro and in vivo studies. J Pharmacol Exp Ther. 2009; 329:827-37. [PubMed 19244096]

120. Dalén P, Alvan G, Wakelkamp M et al. Formation of meprobamate from carisoprodol is catalysed by CYP2C19. Pharmacogenetics. 1996; 6:387-94. [PubMed 8946470]

121. Simon S, D'Andrea C, Wheeler WJ et al. Bioavailability of oral carisoprodol 250 and 350 mg and metabolism to meprobamate: A single-dose crossover study. Curr Ther Res. 2010; 71: 50-9.

122. Reeves RR, Mack JE. Possible dangerous interaction of oxycontin and carisoprodol. Am Fam Physician. 2003; 67:2273. [PubMed 12800958]

123. Meda Pharmaceuticals Inc. Soma Compound with Codeine (carisoprodol, aspirin, and codeine phosphate) tablets prescribing information. Somerset, NJ; 2009 Oct.

124. Meda Pharmaceuticals Inc. Soma Compound (carisoprodol and aspirin) tablets prescribing information. Somerset, NJ; 2009 Oct.

125. Carisoprodol. In: Briggs GG, Freeman RK, Yaffe SJ. Drug in pregnancy and lactation: a reference guide to fetal and neonatal risk. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2011:210-11

126. Food and Drug Administration. Sulfites in foods and drugs. FDA Drug Bull. 1983; 13:12. [PubMed 6604672]

127. Sogn D. The ubiquitous sulfites. JAMA. 1984; 251:2986-7. [IDIS 185969] [PubMed 6716628]

128. Koepke JW, Christopher KL, Chai H et al. Dose-dependent bronchospasm from sulfites in isoetharine. JAMA. 1984; 251:2982-3. [IDIS 185966] [PubMed 6716626]

129. Twarog FJ, Leung DYM. Anaphylaxis to a component of isoetharine (sodium bisulfite). JAMA. 1982; 248:2030-1. [IDIS 158261] [PubMed 7120631]

130. Baker GJ, Collett P, Allen DH. Bronchospasm induced by metabisulphite-containing foods and drugs. Med J Aust. 1981; 2:614-7. [IDIS 146240] [PubMed 7334982]

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a. AHFS drug information 2004. McEvoy GK, ed. Carisoprodol. Bethesda, MD: American Society of Health-System Pharmacists; 2004:1328-9.

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