Last updated: October 14, 2014

Trade Names: Flexeril

Drug Class: Muscle relaxant

Preparations: 5-mg, 7.5-mg, 10-mg tablet

Dose: 15–30 mg/day in three divided doses

Indications: Muscle spasm, fibromyalgia for short periods of time (2-3 weeks)

Mechanism of Action: Centrally acting skeletal muscle relaxant; related to tricyclic antidepressants

Contraindications: Hypersensitivity to cyclobenzaprine. Do not use within 14–21 days of an MAOI. Acute recovery phase of myocardial infarction.

Precautions: As for tricyclics – heart failure, arrhythmias, urinary obstruction, avoid in elderly

Pregnancy Risk: B

Adverse Effects
Common: Anticholinergic effects (dry mouth, difficulty urinating), drowsiness
Less common: Dizziness, blurred vision, weakness, allergy, GI symptoms, headache, confusion, arrhythmias

Drug Interactions
Tricyclic antidepressants: Additive toxicity
CNS depressants (alcohol, benzodiazepines): Increased effect
MAOIs: Hypertensive crisis

Patient Instructions: Causes drowsiness; may impair ability to drive

Comments: Sedative effect is useful at night.

Clinical Pharmacology: Rapid oral absorption; hepatic metabolism and renal elimination of metabolites, half-life 8-37 hours

Cost: $$

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