Orphenadrine Dosing Recommendations
The recommended dosing for orphenadrine is 60 mg administered intravenously or intramuscularly every 12 hours, with oral maintenance therapy of 100 mg twice daily. 1
Parenteral Administration
- Intravenous or intramuscular dosing: 60 mg (one 2 mL vial) every 12 hours 1
- Inspect parenteral solutions visually for particulate matter before administration 1
- For patients transitioning from parenteral to oral therapy, maintain relief with oral tablets 1
Oral Administration
- Standard oral dosing: 100 mg twice daily 1
- This oral regimen is typically used for maintenance therapy after initial parenteral administration 1
Clinical Considerations
- Orphenadrine has anticholinergic properties that can cause both central and peripheral effects 2
- Toxicity can occur at high doses - ingestion of 2-3g in adults has been associated with fatality 2
- Signs of toxicity include confusion, ataxia, seizures, and potential cardiotoxic effects 3
- Recent research suggests that immediate release formulations may have different toxicity profiles than sustained release formulations 4
Monitoring
- Monitor for common adverse effects including drowsiness, tachycardia, and confusion 4
- Be vigilant for signs of anticholinergic toxicity, especially in elderly patients or those with comorbidities 3
Therapeutic Efficacy
- A randomized controlled trial found that adding orphenadrine to naproxen for acute low back pain did not significantly improve functional outcomes compared to naproxen alone 5
- Consider the risk-benefit profile when prescribing, as some studies suggest anticholinergic antiparkinson agents may be superfluous for some patients 6