Comparative Pharmacology
Head-to-head clinical analysis: ORPHENADRINE CITRATE versus ROBAXISAL.
Peer-Reviewed Evidence
Head-to-head clinical analysis: ORPHENADRINE CITRATE versus ROBAXISAL.
ORPHENADRINE CITRATE vs ROBAXISAL
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Orphenadrine citrate is a centrally acting muscle relaxant with anticholinergic properties. Its exact mechanism of action is not fully understood, but it is believed to exert its effects by blocking muscarinic acetylcholine receptors and possibly by acting as an NMDA receptor antagonist. It may also have local anesthetic and antihistaminic properties.
Methocarbamol is a centrally acting muscle relaxant whose exact mechanism is not fully understood, but it is believed to involve general central nervous system depression and inhibition of polysynaptic reflexes in the spinal cord. Aspirin inhibits cyclooxygenase enzymes (COX-1 and COX-2), reducing prostaglandin synthesis, which provides analgesic and anti-inflammatory effects, and also irreversibly inhibits platelet aggregation.
100 mg orally twice daily. Maximum: 250 mg/day.
Oral: 2 tablets (methocarbamol 750 mg / aspirin 650 mg) 4 times daily.
None Documented
None Documented
Terminal elimination half-life is approximately 14 hours (range 11–20 hours) in adults; may be prolonged in elderly or hepatic impairment.
Methocarbamol: 1.0–2.0 hours (prolonged in renal impairment); guaifenesin: approximately 1 hour.
Primarily renal excretion of metabolites; less than 10% excreted unchanged. Also undergoes biliary excretion with fecal elimination of conjugates.
Methocarbamol: renal (primarily as glucuronide and sulfate conjugates, with <2% unchanged); guaifenesin: renal (metabolites, <1% unchanged). No significant biliary/fecal elimination.
Category A/B
Category C
Skeletal Muscle Relaxant
Skeletal Muscle Relaxant