Muscle spasms:

Indications for: Cyclobenzaprine HCl Tablets

Relief of acute muscle spasm, as adjunct to rest and physical therapy.

Clinical Trials:

The approval was based on 8 double-blind controlled clinical studies which included 642 patients comparing cyclobenzaprine HCl 10mg, diazepam, and placebo. The studies evaluated muscle spasm, local pain, and tenderness, limitation of motion, and restriction in activities of daily living. 

  • In 3 of the studies, cyclobenzaprine achieved a significantly greater improvement vs diazepam, while in other studies the improvement was comparable between both treatment arms.

  • Cyclobenzaprine and diazepam demonstrated to have comparable adverse reactions. Dry mouth was observed more frequently in patients treated with cyclobenzaprine, and dizziness was more frequent in patients treated with diazepam.

The efficacy of cyclobenzaprine 5mg was based on 2 seven-day, double-blind, controlled clinical trials which included 1405 patients. 

  • In 1 study, cyclobenzaprine 5mg and 10mg three times daily was compared to placebo; in the other study, cyclobenzaprine 5mg and 2.5mg three times daily was compared to placebo. The primary endpoints were global impression of change, medication helpfulness, and relief from starting backache.

  • Results showed that cyclobenzaprine 5mg achieved statistically significant superiority for all 3 primary endpoints at day 8 and, in the study comparing 5 and 10mg at day 3 or 4 as well. Cyclobenzaprine 10mg also had a similar effect for all endpoints.

Adult Dosage:

≥15yrs: initially 5mg 3 times daily, may increase to 10mg 3 times daily; max 2–3 weeks. Elderly or mild hepatic impairment: initially 5mg and then titrate slowly upward.

Children Dosage:

<15yrs: not established.

Cyclobenzaprine HCl Tablets Contraindications:

Acute post-MI. Arrhythmias, heart block, other conduction disturbances. CHF. Hyperthyroidism. During or within 14 days of MAOIs.

Cyclobenzaprine HCl Tablets Warnings/Precautions:

Moderate-to-severe hepatic impairment: not recommended. Urinary retention. Glaucoma. Increased intraocular pressure. Elderly. Pregnancy (Cat.B). Nursing mothers.

Cyclobenzaprine HCl Tablets Classification:

Muscle relaxant (central).

Cyclobenzaprine HCl Tablets Interactions:

See Contraindications. Hypertensive crisis with MAOIs. Increased risk of serotonin syndrome with other serotonergic drugs (eg, SSRIs, SNRIs, tricyclic antidepressants, tramadol, bupropion, meperidine, verapamil, or MAOIs); monitor closely. Potentiates anticholinergics, alcohol, other CNS depressants. May antagonize guanethidine, clonidine. Tramadol increases seizure risk.

Adverse Reactions:

Drowsiness, dry mouth, dizziness, fatigue, headache, GI upset, asthenia, irritability, nervousness, blurred vision, confusion, arrhythmias, tachycardia, hypotension.

Note:

Formerly known under the brand names Flexeril, Fexmid.

Metabolism:

Extensively metabolized by CYP3A4, 1A2, and to a lesser extent, 2D6.

 

Drug Elimination:

Renal. Half-life: 18 hours (range: 8–37 hours). Plasma clearance: 0.7 L/min.

How Supplied:

Contact supplier.