Cyclobenzaprine(sye-kloe-ben-za-preen)
Amrix, Flexeril
Classification:
Therapeutic: skeletal muscle relaxants (centrally
acting)
Pregnancy Category B
Indications:
Management of acute painful musculoskeletal conditions associated with muscle spasm.
Unlabeled Use: Management of fibromyalgia.
Action:
Reduces tonic somatic muscle activity at the level of the brainstem. Structurally similar to tricyclic antidepressants. Therapeutic Effects: Reduction in muscle spasm and hyperactivity without loss of function.
Pharmacokinetics
Absorption: Well absorbed from the GI tract.
Distribution: Unknown.
Protein Binding: 93%.
Metabolism and Excretion: Mostly metabolized by the liver.
Half-life: 1–3 days.
TIME/ACTION PROFILE (skeletal muscle
relaxation)
ROUTE: PO
ONSET: within 1 hr
PEAK: 3–8 hr
DURATION: 12–24 hr
Full effects may not occur for 1–2 wk
Contraindications/Precautions
Contraindicated in: Hypersensitivity; Should not be used within 14 days of MAO inhibitor therapy; Immediate period after MI; Severe or symptomatic cardiovascular disease; Cardiac conduction disturbances; Hyperthyroidism.
Use Cautiously in: Cardiovascular disease; Geri: Appears on Beers list. Poorly tolerated due to anticholinergic effects; OB, Lactation, Pedi: Pregnancy, lactation, and children 15 yr (safety not established).
Adverse Reactions/Side Effects
CNS: dizziness, drowsiness, confusion, fatigue,
headache, nervousness.
EENT: dry mouth, blurred vision. CV: arrhythmias. GI: constipation,
dyspepsia, nausea, unpleasant taste. GU: urinary retention.
Interactions
Drug-Drug: Additive CNS depression with other
CNS depressants, including alcohol, antihistamines, opioid analgesics, and sedative/ hypnotics. Additive anticholinergic effects with drugs possessing anticholinergic properties, including antihistamines, antidepressants, atropine, disopyramide, haloperidol, and phenothiazines. Avoid use within 14 days of MAO inhibitors (hyperpyretic crisis, seizures, and death may occur). Drug-Natural Products: Concomitant use of kava-kava, valerian, chamomile, or hops can increase CNS depression.
Route/Dosage
PO (Adults): Acute painful musculoskeletal conditions—10 mg 3 times daily (range 20–40 mg/day in 2–4 divided doses; not to exceed 60 mg/day) or extended-release, 15–30 mg once daily. Fibromyalgia—5–40 mg at bedtime (unlabeled).
Availability (generic available)
Tablets: 5 mg, 10 mg. Cost: Generic—5 mg, 10 mg. Extended-release capsules (Amrix): 15 mg, 30 mg.
NURSING IMPLICATIONS
Assessment
- Assess patient for pain, muscle stiffness, and range of motion before and periodically throughout therapy.
- Geri: Assess geriatric patients for anticholinergic effects (sedation and weakness).
Acute pain (Indications)
Impaired physical mobility (Indications)
Risk for injury (Side Effects)
Implementation
- Do not confuse cyclobenzaprine with cyproheptadine.
- PO: May be administered with meals to minimize gastric irritation.
- Swallow extended-release capsules whole; do not open, crush, or chew.
- Instruct patient to take medication as directed; do not take more than the prescribed amount.
- Taken missed doses within 1 hr of time ordered; otherwise, return to normal dose schedule.
- Medication may cause drowsiness, dizziness, and blurred vision. Caution patient to avoid driving or other activities requiring alertness until response to drug is known. Advise patient to avoid concurrent use of alcohol or other CNS depressants with this medication.
- If constipation becomes a problem, advise patient that increasing fluid intake and bulk in diet and stool softeners may alleviate this condition.
- Advise patient to notify health care professional if symptoms of urinary retention (distended abdomen, feeling of fullness, overflow incontinence, voiding small amounts) occur. Inform patient that good oral hygiene, frequent mouth rinses, and sugarless gum or candy may help relieve dry mouth.
- Relief of muscular spasm in acute skeletal muscle conditions. Maximum effects may not be evident for 1–2 wk. Use is usually limited to 2–3 wk; however, has been effective for at least 12 wk in the management of fibromyalgia.
