Orphenadrine is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist that inhibits clonal HERG channels in a concentration-dependent manner, producing an IC of 0.85 μM in HEK cells.Orphenadrine is an antagonist of central and peripheral muscarinic receptors. Attenuation is blocked by mutations in pore residues Y652 or F656. Orphenadrine has antispasmodic, analgesic, and anticholinergic activity and protects against glutamatergic neurotoxicity in vitro and in vivo.Orphenadrine has inhibitory effects on sodium channels and can be used in the treatment of Parkinson's disease.

Orphenadrine decreased CYP2B6 marker activity up to 45-57% in human liver microsomes and up to 80-97% in cell microsomes containing cDNA-expressed CYP2B6. Orphenadrine strongly decreased CYP2D6 marker activity by 80-90%. Orphenadrine also partially decreased the CYP1A2, CYP2A6, CYP3A4, and CYP2C19 marker activities.[4]

Orphenadrine (75 mg/kg/day; i.p.; for 3 days) was associated with a 2-fold induction of total hepatic P-450, a 5- and 2.4-fold induction of androstenedione 16 beta- and 6 beta-hydroxylase activity, respectively, and formation of an orphenadrine-P-450 MI complex. Western blots of orphenadrine-induced microsomes revealed a 20-fold increase in P-450 PB-B/D-immunoreactive protein.[2]