orphenadrine

Therapeutic Classification: skeletal muscle relaxants (centrally acting)

Pharmacologic Classification: diphenhydramine analogues

Indications ⬆ ⬇

BEERS REMS

Adjunct to rest and physical therapy in the treatment of muscle spasm associated with acute painful musculoskeletal conditions.

Action ⬆ ⬇

Skeletal muscle relaxation, probably due to CNS depression.

Therapeutic effects:

Skeletal muscle relaxation, with decreased discomfort.

Pharmacokinetics ⬆ ⬇

Absorption: Readily absorbed after oral and IM administration; IV administration results in complete bioavailability.

Distribution: Unknown.

Metabolism/Excretion: Mostly metabolized by the liver.

Half-Life: 14 hr.

Time/Action Profile ⬆ ⬇

(skeletal muscle effects)

ROUTE	ONSET	PEAK	DURATION
PO-ER	within 1 hr	6–8 hr	12 hr
IM	5 min	30 min	12 hr
IV	immediate	unknown	12 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity;
Bladder neck obstruction, prostatic hyperplasia, glaucoma, myasthenia gravis, peptic ulcer disease, GI obstruction.

Use Cautiously in:

Underlying cardiovascular disease;
Renal impairment;
OB: Safety not established in pregnancy;
Lactation: Safety not established in breastfeeding;
Pedi: Safety and effectiveness not established in children;
Geri: Appears on Beers list. ↑ risk of anticholinergic adverse reactions, sedation, and fractures in older adults. Avoid use in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

CV: orthostatic hypotension, tachycardia

EENT: blurred vision, dry eyes

GI: constipation, dry mouth

GU: urinary retention

Neuro: CNS excitation, confusion, dizziness, drowsiness

Interactions ⬆ ⬇

Drug-drug:

Concurrent 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.

Drug-Natural Products:

Kava-kava, valerian, chamomile, or hops can ↑ CNS depression.

Route/Dosage ⬆ ⬇

PO (Adults ): 100 mg twice daily.
IV IM (Adults ): 60 mg every 12 hr.

Availability ⬆ ⬇

(Generic available)

Extended-release tablets: 100 mg
Solution for injection: 30 mg/mL

Assessment ⬆ ⬇

Geri: Assess geriatric patients for anticholinergic adverse effects (delirium, acute confusion, dizziness, dry mouth, blurred vision, urinary retention, constipation, tachycardia) and sedation.
Assess patient for pain, muscle stiffness, and range of motion before and periodically throughout therapy.

Lab Test Considerations:

Monitor CBC and renal and hepatic function tests periodically during prolonged therapy.

Implementation ⬆ ⬇

Provide safety measures as indicated. Supervise ambulation and transfer of patients.
PO: DNC: Do not break, crush, or chew extended-release tablets.

IV Administration:

IV Push: May be administered undiluted.

Patient/Family Teaching ⬆ ⬇

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.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
Emphasize the importance of routine follow-up exams to monitor progress.

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Pronunciation ⬇

Classifications ⬆ ⬇