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Pregnancy Category: C
Pharmacologic: diphenhydramine analogues
ClassificationTherapeutic: skeletal muscle relaxants
Pharmacologic: diphenhydramine analogues
Adjunct to rest and physical therapy in the treatment of muscle spasm associated with acute painful musculoskeletal conditions.Adjunct therapy of Parkinson’s disease (Canadian labeling only).
Skeletal muscle relaxation, probably due to CNS depression.
Skeletal muscle relaxation, with decreased discomfort.
Absorption: Readily absorbed after oral and IM administration; IV administration results in complete bioavailability.
Metabolism and Excretion: Mostly metabolized by the liver.
Half-life: 14 hr.
Time/action profile (skeletal muscle effects)
|PO-ER||within 1 hr||6–8 hr||12 hr|
|IM||5 min||30 min||12 hr|
Contraindicated in: Hypersensitivity; Bladder neck obstruction, prostatic hyperplasia, glaucoma, myasthenia gravis, peptic ulcer disease, GI obstruction.
Use Cautiously in: Underlying cardiovascular disease; Impaired renal function; Obstetric / Lactation / Pediatric: Safety not established; Geriatric: Appears on Beers list; more susceptible to sedation and anticholinergic effects.
Adverse Reactions/Side Effects
Central nervous system
- CNS excitation
Ear, Eye, Nose, Throat
- blurred vision
- dry eyes
- orthostatic hypotension
- dry mouth
- urinary retention
Drug-Drug interactionConcurrent use of other anticholinergics ↑ risk of anticholinergic side effects.↑ risk of CNS depression with other CNS depressants including alcohol, antihistamines, antidepressants, sedative/hypnotics, or opioid analgesics.Kava-kava, valerian, chamomile, or hops can ↑ CNS depression.
Skeletal muscle relaxation
Oral (Adults) 100 mg twice daily.
Intravenous Intramuscular (Adults) 60 mg q 12 hr.
Adjunctive therapy of Parkinson's disease
Oral (Adults) 50 mg 3 times daily (lower doses if used with other agents).
Availability (generic available)
Tablets : 100 mgOTC
Extended-release tablets: 100 mg
Injection: 30 mg/mL
- Geriatric: Assess geriatric patients for anticholinergic adverse effects (delirium, acute confusion, dizziness, dry mouth, blurred vision, urinary retention, constipation, tachycardia) and sedation.
- Skeletal Muscle Relaxant: Assess patient for pain, muscle stiffness, and range of motion before and periodically throughout therapy.
- Parkinson's Disease: Assess parkinsonian and extrapyramidal symptoms (restlessness or desire to keep moving, rigidity, tremors, pill rolling, mask-like face, shuffling gait, muscle spasms, twisting motions, difficulty speaking or swallowing, loss of balance control) prior to and throughout therapy.
- Lab Test Considerations: Monitor CBC and renal and hepatic function tests periodically during prolonged therapy.
Potential Nursing DiagnosesAcute pain (Indications)
Impaired physical mobility (Indications)
Risk for injury (Side Effects)
- Provide safety measures as indicated. Supervise ambulation and transfer of patients.
- Oral: Do not break, crush or chew extended-release tablets.
- May be administered undiluted.
- Concentration: 30 mg/mL.
- Advise patient to take medication as directed. Take missed doses within 1 hr; if not, return to regular dosing schedule. Do not double doses.
- Encourage patient to comply with additional therapies prescribed for muscle spasm (rest, physical therapy, heat).
- Medication may cause dizziness, drowsiness, and blurred vision. Advise patient to avoid driving and other activities requiring alertness until response to drug is known.
- Instruct patient to make position changes slowly to minimize orthostatic hypotension.
- Advise patient to avoid concurrent use of alcohol and other CNS depressants while taking this medication.
- Emphasize the importance of routine follow-up exams to monitor progress.
- Decreased musculoskeletal pain and muscle spasticity.
- Increased range of motion.
- Decrease in tremors and rigidity and an improvement in gait and balance.
a trademark for a skeletal muscle relaxant with anticholinergic properties (orphenadrine citrate).