What is the recommended dosing for orphenadrine (muscle relaxant) in adults?

Orphenadrine Dosing for Adults

The recommended dosing for orphenadrine in adults is 100 mg orally twice daily, or one 60 mg injection (intravenously or intramuscularly) every 12 hours. 1

Dosage Forms and Administration

• Oral tablets: 100 mg twice daily 1
• Parenteral: 60 mg (2 mL vial) intravenously or intramuscularly every 12 hours 1
• Parenteral administration can be used initially, with maintenance therapy continued using oral tablets 1

Clinical Considerations

• Orphenadrine is an anticholinergic drug with both peripheral and central effects 2
• Inspect parenteral solutions visually for particulate matter before administration 1
• Monitor for anticholinergic side effects, which may include confusion, drowsiness, tachycardia, and dry mouth 3

Safety Considerations

• Toxic doses can cause significant anticholinergic toxicity - doses of 2-3g have been associated with fatality in adults 3
• Clinical features of overdose include:
  • Central nervous system effects: confusion, drowsiness, agitation, seizures 3
  • Cardiovascular effects: sinus tachycardia, potential for ventricular arrhythmias at high doses 2, 4
  • Other effects: rhabdomyolysis has been reported in severe overdose cases 3

Drug Interactions

• Orphenadrine can interact with other medications, particularly:
  • Antipsychotics: Orphenadrine may lower plasma concentrations of chlorpromazine and potentially reduce its effectiveness 5
  • Orphenadrine should not be prescribed routinely with major tranquilizers without individual assessment 5

Formulation Considerations

• Available in both immediate and sustained release formulations 4
• Recent toxicology data suggests formulation may impact outcomes in overdose cases, with potentially less toxicity from sustained release products 4