Orphenadrine for Muscle Spasms and Pain
Orphenadrine is indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute painful musculoskeletal conditions, with a recommended dosage of 100 mg orally twice daily. 1
Mechanism of Action and Clinical Use
- Orphenadrine is a centrally acting skeletal muscle relaxant with anticholinergic properties, similar in structure to diphenhydramine 2
- The precise mechanism of action is unclear but appears to include anticholinergic effects 2
- It is specifically indicated for short-term relief of discomfort associated with acute painful musculoskeletal conditions 1
- Orphenadrine has shown effectiveness in reducing the frequency, duration, and pain of muscle cramps 3
Dosage Recommendations
- Oral administration: 100 mg twice daily 1
- Parenteral administration: 60 mg (one 2 mL vial) intravenously or intramuscularly every 12 hours 1
- Treatment duration should be limited to acute conditions, as long-term efficacy data is limited 1
- Relief from parenteral administration may be maintained with oral therapy of 100 mg twice daily 1
Efficacy
- Orphenadrine has demonstrated superior efficacy compared to placebo in treating painful muscle spasms, with 66% of patients reporting improvement versus 53% for placebo 4
- The combination of orphenadrine with paracetamol has shown even better results (71% improvement) and is superior to paracetamol alone 4, 5
- Studies support orphenadrine's effectiveness as both a muscle relaxant and mild analgesic in conditions associated with muscle spasm 5
Contraindications
- Orphenadrine is contraindicated in patients with: 2
- Gastrointestinal tract obstruction
- Stenosing peptic ulcer disease
- Prostatic hypertrophy or bladder outlet obstruction
- Glaucoma
- Myasthenia gravis
Precautions and Special Populations
- Use with caution in patients with: 2
- Tachycardia or cardiac arrhythmias
- Cardiac decompensation
- Coronary insufficiency
- Elderly patients (increased sensitivity to anticholinergic effects)
- Hold orphenadrine on the day of surgical procedures due to potential cardiovascular instability 6
- Monitor for drug interactions with other medications having anticholinergic properties 2
Adverse Effects
- Common side effects include anticholinergic symptoms: 2
- Confusion and anxiety
- Tremors
- Urinary retention
- Dry mouth and constipation
- Cardiovascular instability
- In overdose cases, symptoms may include drowsiness (59%), sinus tachycardia (37%), and confusion (33%) 7
- Most adverse effects are dose-related and more common with immediate-release formulations compared to sustained-release formulations 7
Monitoring Recommendations
- Monitor for anticholinergic side effects, particularly in elderly patients 2
- Assess for potential drug interactions with other medications that have anticholinergic properties 2
- Evaluate effectiveness in reducing muscle spasm and pain within the first week of treatment 4
- Consider alternative treatments if significant improvement is not observed or if side effects are intolerable 8
Clinical Pearls
- Orphenadrine may be more effective when combined with non-pharmacological measures like rest and physical therapy 1
- The combination of orphenadrine with paracetamol has demonstrated superior efficacy compared to either agent alone 4, 5
- For perioperative management, hold orphenadrine on the day of surgery 6
- Short-term use is preferred to minimize the risk of adverse effects 8