Home Drug Guide Orphenadrine Citrate

Drug Guide

Generic Name

Orphenadrine Citrate

Brand Names Norflex

Classification

Therapeutic: Muscle relaxant

Pharmacological: Anticholinergic agent

FDA Approved Indications

Relief of pain and discomfort caused by musculoskeletal conditions with associated muscle spasms

Mechanism of Action

Orphenadrine acts centrally as an anticholinergic and antihistaminic agent, reducing muscle spasm and pain by interfering with nerve impulses involved in muscle contraction.

Dosage and Administration

Adult: 100 mg twice daily, may be adjusted based on response and tolerability

Pediatric: Not recommended for children under 15 years

Geriatric: Start at lower doses due to increased sensitivity, monitor closely for adverse effects

Renal Impairment: Use with caution; dose adjustment may be necessary

Hepatic Impairment: Use with caution; no specific dose adjustment recommended but monitor for increased effects

Pharmacokinetics

Absorption: Well absorbed orally

Distribution: Widely distributed, crosses the blood-brain barrier

Metabolism: Hepatic metabolism, partial via CYP450 enzymes

Excretion: Primarily renal

Half Life: 4-6 hours

Contraindications

Hypersensitivity to orphenadrine or other anticholinergics
Myasthenia gravis
Glaucoma

Precautions

Use with caution in elderly, patients with urinary retention, prostatic hypertrophy, history of cardiac disease, or in those taking other CNS depressants

Adverse Reactions - Common

Drowsiness (Common)
Dizziness (Common)
Dry mouth (Common)
Blurred vision (Common)

Adverse Reactions - Serious

Anaphylaxis (Rare)
Confusion in elderly (Less common)
Tachycardia (Less common)

Drug-Drug Interactions

CNS depressants (enhanced sedation)
MAO inhibitors (potential hypertensive crisis)
Other anticholinergic drugs (additive effects)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for effectiveness and adverse effects, including sedation, anticholinergic effects, and signs of CNS depression

Diagnoses:

Risk for injury (due to dizziness or sedation)
Ineffective coping (due to adverse mental effects)

Implementation: Administer with food to decrease gastrointestinal upset, monitor for signs of overdose or adverse reactions

Evaluation: Assess pain relief, muscle spasm reduction, and absence of adverse effects

Patient/Family Teaching

Advise on possible drowsiness and the need to avoid driving or operating machinery until effects are known
Encourage adequate fluid intake to prevent dry mouth
Report worsening symptoms or adverse reactions

Special Considerations

Black Box Warnings: N/A

Genetic Factors: None established

Lab Test Interference: None significant

Overdose Management

Signs/Symptoms: Dry mouth, blurred vision, urinary retention, hallucinations, seizures, coma, tachycardia, difficulty breathing

Treatment: Supportive care, activated charcoal if ingestion was recent, symptomatic treatment, atropine may be used for anticholinergic toxicity

Storage and Handling

Storage: Store at room temperature (15-30°C), away from moisture and light

Stability: Stable under recommended storage conditions for the shelf life specified on the packaging