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Cyclobenzaprine hydrochloride
Cyclobenzaprine hydrochloride (Flexeril)
Cyclobenzaprine hydrochloride
(sye-kloh-BENZ-ah-preen)
Pregnancy Category: B Alti-Cyclobenzaprine Apo-Cyclobenzaprine Flexeril Novo-Cycloprine Nu-Cyclobenzaprine PMS-Cyclobenzaprine (Rx)

Classification: Skeletal muscle relaxant, centrally acting

See Also: See also Skeletal Muscle Relaxants, Centrally Acting.

Action/Kinetics: Related to the tricyclic antidepressants; possesses both sedative and anticholinergic properties. Thought to inhibit reflexes by reducing tonic somatic motor activity. Onset: 1 hr. Time to peak plasma levels: 4-6 hr. Therapeutic plasma levels: 20-30 ng/mL. Duration: 12-24 hr. t1/2: 1-3 days. Highly bound to plasma protein. Inactive metabolites are excreted in the urine.

Uses: Adjunct to rest and physical therapy for relief of muscle spasms associated with acute and/or painful musculoskeletal conditions. Not indicated for the treatment of spastic diseases or for cerebral palsy. Investigational: Adjunct in the treatment of fibrositis syndrome.

Contraindications: Hypersensitivity. Arrhythmias, heart block or conduction disturbances, CHF, or during acute recovery phase of MI. Hyperthyroidism. Concomitant use of MAO inhibitors or within 14 days of their discontinuation.

Special Concerns: Safe use during lactation and in children under age 15 has not been established. Due to atropine-like effects, use with caution in situations where cholinergic blockade is not desired (e.g., history of urinary retention, angle-closure glaucoma, increased intraocular pressure). Geriatric clients may be more sensitive to cholinergic blockade.

Side Effects: Since cyclobenzaprine resembles tricyclic antidepressants, side effects to these drugs should also be noted. GI: Dry mouth, N&V;, constipation, dyspepsia, unpleasant taste, anorexia, diarrhea, GI pain, gastritis, thirst, flatulence, ageusia, paralytic ileus, discoloration of tongue, stomatitis, parotid swelling. CNS: Drowsiness, dizziness, fatigue, asthenia, blurred vision, nervousness, headache, convulsions ataxia, vertigo, dysarthria, paresthesia, hypertonia, tremors, malaise, abnormal gait, delusions, Bell's palsy, alteration in EEG patterns, extrapyramidal symptoms. Psychiatric symptoms include: confusion, insomnia, disorientation, depressed mood, abnormal sensations, anxiety, agitation, abnormal thinking or dreaming, excitement, hallucinations. CV: Tachycardia, syncope, arrhythmias vasodilation, palpitations, hypotension, edema, chest pain, hypertension, MI, heart block, stroke. GU: Urinary frequency or retention, impaired urination, dilation of urinary tract, impotence, decreased or increased libido, testicular swelling, gynecomastia, breast enlargement, galactorrhea. Dermatologic: Sweating, skin rashes, urticaria, pruritus, photosensitivity, alopecia. Musculoskeletal: Muscle twitching, weakness, myalgia. Hematologic: Purpura, bone marrow depression, leukopenia, eosinophilia, thrombocytopenia. Hepatic: Abnormal liver function, hepatitis, jaundice, cholestasis. Miscellaneous: Tinnitus, diplopia, peripheral neuropathy, increase and decrease of blood sugar, weight gain or loss, edema of the face and tongue inappropriate ADH syndrome, dyspnea.

Overdose Management: Symptoms: Temporary confusion, disturbed concentration, transient visual hallucinations, agitation, hyperactive reflexes, muscle rigidity, vomiting, hyperpyrexia. Also, drowsiness, hypothermia, tachycardia, cardiac arrhythmias such as bundle branch block, ECG evidence of impaired conduction CHF, dilated pupils, seizures, severe hypotension stupor, coma paradoxical diaphoresis. Treatment: In addition to the treatment outlined in , for physostigmine salicylate, 1-3 mg IV may be used to reverse symptoms of severe cholinergic blockade.

Drug Interactions: NOTE: Because of the similarity of cyclobenzaprine to tricyclic antidepressants, the drug interactions for tricyclics should also be consulted. Anticholinergics / Additive anticholinergic side effects CNS depressants / Additive depressant effects Guanethidine / Cyclobenzaprine may block effect MAO inhibitors / Hypertensive crisis, severe convulsions Tricyclic antidepressants / Additive side effects

How Supplied: Tablet: 10 mg

Dosage
•Tablets Skeletal muscle disorders.
Adults: 20-40 mg/day in three to four divided doses (usual: 10 mg t.i.d.), up to a maximum of 60 mg/day in divided doses.