cyclobenzaprine hydrochloride

Action

Unclear. Thought to act primarily at brain stem (and to a lesser extent at spinal cord level) to relieve skeletal muscle spasms of local origin without altering muscle function.

Availability

Capsules (extended-release): 15 mg, 30 mg

Tablets: 5 mg, 7.5 mg, 10 mg

Indications and dosages

➣ Adjunct to rest and physical therapy to relieve muscle spasm associated with acute, painful musculoskeletal conditions

Adults: 5 mg P.O. t.i.d. (immediate-release tablet). May increase to 10 mg P.O. t.i.d. (immediate-release tablet) as needed. Or, 15 mg (extended-release capsule) P.O. daily; some patients may need up to 30 mg/day, given as one 30-mg (extended-release capsule) P.O. daily or two 15-mg (extended-release capsules) P.O. daily.

Contraindications

• Hypersensitivity to drug

• Acute recovery phase after myocardial infarction (MI)

• Heart failure

• Arrhythmias

• Hyperthyroidism

• MAO inhibitor use within past 14 days

Precautions

Use cautiously in:

• cardiovascular disease, closed-angle glaucoma, hepatic impairment, increased intraocular pressure, urinary retention

• elderly patients

• pregnant or breastfeeding patients

• children younger than age 15.

Administration

See Don't give within 14 days of MAO inhibitor. Drug interaction may cause hypertensive crisis and severe seizures.

• Give extended-release capsule at approximately the same time each day.

• Know that drug shouldn't be used for more than 3 weeks.

• Be aware that drug may not be first-line agent for elderly patients because of its anticholinergic effects.

Adverse reactions

CNS: dizziness, drowsiness, syncope, confusion, fatigue, headache, nervousness, decreased mental acuity, irritability, weakness, insomnia, depression, disorientation, delusions, peripheral neuropathy, abnormal gait, Bell's palsy, EEG changes, extrapyramidal symptoms, cerebrovascular accident

CV: vasodilation, tachycardia, chest pain, hypotension, MI, heart block

EENT: blurred vision

GI: nausea, constipation, dyspepsia, swollen parotid glands, mouth inflammation, discolored tongue, dry mouth, paralytic ileus

GU: galactorrhea, urinary retention, urinary frequency, gynecomastia, testicular swelling, libido changes, erectile dysfunction

Hematologic: purpura, eosinophilia, bone marrow depression, leukopenia, thrombocytopenia

Metabolic: hyperglycemia, hypoglycemia, syndrome of inappropriate diuretic hormone secretion

Musculoskeletal: muscle ache

Respiratory: dyspnea

Skin: photosensitization, alopecia, angioedema

Other: unpleasant taste, weight gain or loss, edema

Interactions

Drug-drug. Anticholinergics, anti-cholinergic-like drugs (including anti-depressants, antihistamines, disopyramide, haloperidol, phenothiazines): additive anticholinergic effects

Antihistamines, CNS depressants, opioids, sedative-hypnotics: additive CNS depression

Guanadrel, guanethidine: reduction in or blockage of these drugs' actions

MAO inhibitors: hyperpyretic crisis, seizures, death

Drug-herbs. Chamomile, hops, kava, skullcap, valerian: increased CNS depression

Drug-behaviors. Alcohol use: increased CNS depression

Patient monitoring

• Assess for adverse CNS effects, such as drowsiness, dizziness, and decreased mental acuity.

• Monitor patient for evidence of drug interactions, especially when giving drug with CNS depressants.

Patient teaching

• Tell patient to take extended-release capsule at approximately the same time each day.

• Tell patient that drug may cause dry mouth.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, alertness, and vision.

• Advise patient not to use alcohol, sedatives, pain medications, over-the-counter preparations, or herbs without consulting prescriber.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, herbs, and behaviors mentioned above.