Drug information of Cyclobenzaprine


Drug group:

Cyclobenzaprine is a skeletal muscle relaxant and a central nervous system (CNS) depressant. Cyclobenzaprine acts on the locus coeruleus where it results in increased norepinephrine release, potentially through the gamma fibers which innervate and inhibit the alpha motor neurons in the ventral horn of the spinal cord.

 It is structurally similar to Amitriptyline, differing by only one double bond.

Mechanism of effect

Like other tricyclic antidepressants, cyclobenzaprine exhibits anticholinergic activity, potentiation of norepinephrine, and antagonism of reserpine. Cyclobenzaprine does not directly act on the neuromuscular junction or the muscle but relieves muscle spasms through a central action, possibly at the brain stem level.

Cyclobenzaprine binds to the serotonin receptor and is considered a 5-HT2 receptor antagonist that reduces muscle tone by decreasing the activity of descending serotonergic neurons.


Cyclobenzaprine, closely related to the antidepressant amitriptyline, is used as a skeletal muscle relaxant to reduce pain and tenderness and improve mobility. Unlike dantrolene, cyclobenzaprine cannot be used to treat muscle spasm secondary to cerebral or spinal cord disease.


Onset: 1 hr

Duration: 12-24 hr

Bioavailability: 33-55%

Peak plasma time: 7-8 hr

Peak plasma concentration: 15-25 ng/mL

Protein bound: 93%


Hepatic via CYP3A4, 1A2, and 2D6; may undergo enterohepatic recirculation

Half-life: 8-37 hours (immediate release); 32-33 hr (extended release)

Excretion: Urine, feces

Drug indications



Muscle Spasm


Immediate-release tablet

  • 5 mg PO q8hr; may increase dose to 7.5-10 mg PO q8hr PRN

Extended-release capsule

  • 15 mg PO qDay; some patients may require up to 30 mg PO qDay


Immediate-release tablet

  • >15 years: 5 mg PO q8hr; may increase dose to 7.5-10 mg PO q8hr PRN

Extended-release capsule

  • >18 years: 15 mg PO qDay; some patients may require up to 30 mg PO qDay


  • Use only for short periods (2-3 wk)
  • Use caution in urinary retention, narrow-angle glaucoma or IOP, or concomitant use of other anticholinergic drugs
  • May cause drowsiness/dizziness; do not ingest alcohol or other CNS depressants; may impair ability to operate heavy machinery
  • May take with food to avoid stomach upset
  • Serotonin syndrome reported when coadministered with other drugs that increase serotonin (eg, SSRIs, SNRIs, TCAs, tramadol, bupropion, meperidine, verapamil, or MAO inhibitors [see also Contraindications])
  • Not effective for treatment of spasticity associated with cerebral/spinal cord disease or for pediatric cerebral palsy
  • Elderly patients may be more prone to adverse effects and require dose/frequency reduction
  • Use immediate release with caution in hepatic impairment; extended-release form not recommended with hepatic impairment

Points of recommendation

Take the medicine at the same time each day.

Do not crush, chew, break, or open an extended-release capsule. Swallow it whole.

You may have unpleasant withdrawal symptoms when you stop taking cyclobenzaprine after long-term use. Ask your doctor how to avoid withdrawal symptoms when you stop using this medicine.

Pregnancy level


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