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Action/Kinetics:
Inhibits polysynaptic reflexes at both the spinal cord and subcortical areas of the brain. Effects may also be due to sedation.
Onset: 1 hr.
Time to peak blood levels: 1-2 hr.
Peak serum levels: 10-30 mcg/mL (after 750-mg dose).
Duration: 3-4 hr.
t
1/2: 1 hr. Metabolized in the liver and inactive metabolites excreted in the urine.
Uses:
As adjunct to rest, physical therapy, and other approaches for treatment of acute, painful musculoskeletal conditions (e.g., muscle spasms, sprains, muscle strain).
Special Concerns:
Use during pregnancy only if benefits clearly outweigh risks. Use with caution in clients with known allergies or a history of allergic reactions to drugs.
Side Effects:
CNS: Dizziness, drowsiness, lightheadedness, overstimulation, malaise.
Dermatologic: Allergic-type skin rashes, petechiae, ecchymoses (rare).
GI: GI upset, GI bleeding (rare).
Allergic Reactions:
Angioneurotic edema, anaphylaxis (rare).
Miscellaneous: Discoloration of urine, liver damage.
Overdose Management:
Symptoms: N&V;, diarrhea, drowsiness, dizziness, lightheadedness, headache, malaise, sluggishness. May be followed by marked loss of muscle tone (voluntary movement may be impossible), decreased or absent deep tendon reflexes, respiratory depression, decreased BP.
Treatment: Supportive.
Additional Drug Interactions:
Isoniazid
plasma levels of chlorzoxazone due to
liver breakdown.
How Supplied:
Tablet: 250 mg, 500 mg
Dosage
?Tablets
Skeletal muscle disorders.
Adults: 250-750 mg t.i.d.-q.i.d. with meals and at bedtime;
pediatric: 125-500 mg t.i.d.-q.i.d. (or 20 mg/kg in three to four divided doses daily).
