carisoprodol, Soma

 Indications

Adjunct to rest and physical therapy in the treatment of

muscle spasm associated with acute painful musculoskeletal

conditions.

Action

Skeletal muscle relaxation, probably due to CNS depression.

Therapeutic Effects: Skeletal muscle relaxation.

Pharmacokinetics

Absorption: Well absorbed after oral administration.

Distribution: Crosses the placenta; high concentrations

in breast milk.

Metabolism and Excretion: Mostly metabolized

by the liver via CYP2C19 to meprobamate; 2% of

Whites, 4% of Blacks, and 14% of Asians have CYP2C19

genotype that results in reduced metabolism of carisoprodol

(poor metabolizers) into its active metabolite

(may result inqsedation).

Half-life: 8 hr.

TIME/ACTION PROFILE (skeletal muscle

relaxation)

ROUTE ONSET PEAK DURATION

PO 30 min unknown 4–6 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity to carisoprodol

or to meprobamate; Porphyria or suspected porphyria.

Use Cautiously in: Severe liver or kidney disease;

OB, Lactation, Pedi: Safety not established for pregnant

women, breast feeding infants, or children 16 yr;

Geri: Poorly tolerated due to anticholinergic effects. Appears

on Beers list.

Adverse Reactions/Side Effects

CNS: dizziness, drowsiness, agitation, ataxia, depression,

headache, insomnia, irritability, syncope. Resp:

asthma attacks. CV: hypotension, tachycardia. GI: epigastric

distress, hiccups, nausea, vomiting. Derm:

flushing, rashes. Hemat: eosinophilia, leukopenia.

Misc: ANAPHYLACTIC SHOCK, fever, psychological dependence,

severe idiosyncratic reaction.

Interactions

Drug-Drug: Additive CNS depression with other CNS

depressants including alcohol, antihistamines,

opioid analgesics, and sedative/hypnotics.

Drug-Natural Products: Concomitant use of

kava-kava, valerian, skullcap, chamomile, or

hops canqCNS depression. 

Route/Dosage

PO (Adults 16 yr): 250–350 mg 4 times daily for

no longer than 2–3 wk.

Availability (generic available)

Tablets: 250 mg, 350 mg. Cost: Generic—250 mg

$330.59/100, 350 mg $59.62/100. In combination

with: aspirin and codeine (generic only). See

Appendix B.