orphenadrine hydrochloride: clinical use

Prescribing considerations

• Confirm that symptoms represent parkinsonism rather than tardive dyskinesia, which may worsen with orphenadrine.
• Older adults may be particularly susceptible to cognitive and peripheral anticholinergic effects.
• Use caution with tachycardia, hypertension and cardiac, renal or hepatic dysfunction.
• Avoid abrupt withdrawal and remain alert to reported misuse potential.
• Review total anticholinergic burden and continuing clinical benefit.

Contraindications and cautions

• Hypersensitivity to orphenadrine or an excipient
• Prostatic hypertrophy or urinary retention
• Tardive dyskinesia
• Porphyria
• Paralytic ileus or pyloric stenosis
• Glaucoma or a narrow anterior-chamber angle
• Risk of hyperpyrexia
• Hereditary fructose intolerance for this oral solution

Monitoring

• Symptomatic response and continuing treatment need
• Cognition, hallucinations, sedation and coordination
• Heart rate where tachycardia is a concern
• Bowel function and urinary retention
• Visual symptoms and possible raised intraocular pressure
• Cumulative anticholinergic adverse effects, especially in older adults

Clinical pharmacology

Orphenadrine is an antimuscarinic agent with weak antihistamine and local-anaesthetic activity. It is absorbed from the gastrointestinal tract, distributed into tissues, extensively metabolised and excreted mainly in urine as metabolites; a half-life of about 14 hours has been reported.

Formulation and product differences

• The selected product is an oral solution and may be useful when solid oral preparations are unsuitable.
• It contains maltitol and sorbitol and must not be used in hereditary fructose intolerance; these excipients may also have a laxative effect.
• Parabens and benzyl alcohol can cause allergic reactions. It also contains a very small amount of ethanol.
• The solution is supplied in an amber glass bottle and should be protected from direct sunlight.

Oral solution

Route: Oral

Strengths: 50 mg/5 mL