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CYCLOBENZAPRINE HYDROCHLORIDE

Medical Diagnosis and Drugs, Medications
CYCLOBENZAPRINE HYDROCHLORIDE
(sye-kloe-ben'za-preen)
Cycoflex, Flexeril
Classifications: skeletal muscle relaxant, central acting;
Therapeutic: skeletal muscle relaxant; antispasmodic
Pregnancy Category: B

Availability

5 mg, 10 mg tablets

Action

Relieves skeletal muscle spasm of local origin without interfering with muscle function. Believed to act primarily within CNS at brain stem; some action at spinal cord level is also probable. It is not a peripheral neuromuscular blocker. Depresses tonic somatic motor activity, although both gamma and alpha motor neurons are affected.

Therapeutic Effect

Cyclobenzaprine is a skeletal muscle relaxant approved for the relief of muscle spasm associated with acute, painful musculoskeletal conditions.

Uses

Short-term adjunct to rest and physical therapy for relief of muscle spasm associated with acute musculoskeletal conditions. Not effective in treatment of spasticity associated with cerebral palsy or cerebral or cord disease.

Contraindications

Acute recovery phase of MI, patients with cardiac arrhythmias, heart block or conduction disturbances, QT prolongation; CHF, hyperthyroidism; closed-angle glaucoma, increased intraocular pressure; moderate or severe hepatic impairment; MAOI therapy; cerebral palsy. Use for periods longer than 2 or 3 wk not recommended by manufacturer. Safe use in children <15 y not established.

Cautious Use

Patients receiving anticholinergic medications; prostatic hypertrophy, history of urinary retention, seizures; cardiovascular disease; mild hepatic impairment; older adults, debilitated patients; history of psychiatric illness; pregnancy (category B), lactation.

Route & Dosage

Muscle Spasm
Adult: PO 5–10 mg t.i.d. (max: 60 mg/d)
Geriatric: Start with 5 mg

Mild Hepatic Impairment
Start with 5 mg.

Moderate to Severe Hepatic Impairment
Not recommended.

Administration

Oral
  • Do not administer drug if patient is receiving an MAO INHIBITOR (e.g., furazolidone, isocarboxazid, pargyline, tranylcypromine).
  • Cyclobenzaprine is intended for short-term (2 or 3 wk) use.
  • Store in tightly closed container, preferably at 15°–30° C (59°–86° F) unless otherwise directed by manufacturer.

Adverse Effects (≥1%)

Body as a Whole: Edema of tongue and face, sweating, myalgia, hepatitis, alopecia. Shares toxic potential of tricyclic antidepressants. CV: Tachycardia, syncope, palpitation, vasodilation, chest pain, orthostatic hypotension, dyspnea; with high doses, possibility of severe arrhythmias. GI: Dry mouth, indigestion, unpleasant taste, coated tongue, tongue discoloration, vomiting, anorexia, abdominal pain, flatulence, diarrhea, paralytic ileus. CNS: Drowsiness, dizziness, weakness, fatigue, asthenia, paresthesias, tremors, muscle twitching, insomnia, euphoria, disorientation, mania, ataxia. Skin: Pruritus, urticaria, skin rash. Urogenital: Increased or decreased libido, impotence.

Interactions

Drug: Alcohol, barbiturates, other cns depressants enhance CNS depression; potentiates anticholinergic effects of phenothiazine and other anticholinergics; mao inhibitors may precipitate hypertensive crisis—use with extreme caution.

Pharmacokinetics

Absorption: Well absorbed from GI tract with some first-pass elimination in liver. Onset: 1 h. Peak: 3–8 h. Duration: 12–24 h. Distribution: Highly protein bound (93%). Metabolism: In liver to inactive metabolites. Elimination: Slowly excreted in urine with some elimination in feces; may be excreted in breast milk. Half-Life: 1–3 d.

Nursing Implications

Assessment & Drug Effects

  • Supervision of ambulation may be indicated, especially in the older adult because of risk of drowsiness and dizziness.
  • Withhold drug and notify physician if signs of hypersensitivity (e.g., pruritus, urticaria, rash, appear).

Patient & Family Education

  • Avoid driving and other potentially hazardous activities until reaction to drug is known. Adverse effects include drowsiness and dizziness.
  • Avoid alcohol and other CNS DEPRESSANTS (unless otherwise directed by physician) because cyclobenzaprine enhances their effects.
  • Dry mouth may be relieved by increasing total fluid intake (if not contraindicated).
  • Keep physician informed of therapeutic effectiveness. Spasmolytic effect usually begins within 1 or 2 d and may be manifested by lessening of pain and tenderness, increase in range of motion, and ability to perform ADL.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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