Cyclobenzaprine Hydrochloride (Flexeril)


  • Muscle relaxant


  • Centrally acting skeletal muscle relaxant


  • Skeletal muscle spasms associated with painful musculoskeletal conditions

  • Unlabeled use:

    • fibrositis syndrome: 10-40mg/day in divided doses


  • Concomitant administration with monoamine oxidase inhibitors (MAOI) or with 14 days post discontinuing MAOI use.

  • Acute recovery phase of myocardial infarction.

  • Patients with arrhythmias, heart block, or conduction disorders.

  • Patients with congestive heart failure.

  • Patients with hyperthyroidism.


  • Pregnancy category B

  • Structurally related to tricyclic antidepressants.

  • Use with caution in patients with a history of urinary retention, closed-angle glaucoma and increased intraocular pressure due to possible anticholinergic effects.

  • Will impair higher order motor function, therefore use caution when operating machinery or automobiles.

  • Use for only short-term treatment (2-3 weeks).

  • Use with caution when administering with other CNS depressive medications.

  • Do not drink alcohol when using cyclobenzaprine.

  Adverse Reactions (Side Effects):

Central nervous system: drowsiness, dizziness, fatigue, blurred vision, headache, nervousness

Gastrointestinal: nausea, constipation, dyspepsia, unpleasant taste

Dry mouth


  • Administered orally (tablets, capsules, liquid) or rectally

  • Adult:

    • 20-40mg per day in divided doses (no greater than 60mg per day)

    • Do not use for periods greater than three weeks

    • Not recommended for children under 15 years old.

  • Fibrositis syndrome:

    • 10-40mg/day in divided doses

Source: Operational Medicine 2001,  Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300  

OB-GYN 101: Introductory Obstetrics & Gynecology
2003, 2004, 2005 Medical Education Division, Brookside Associates, Ltd.
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