Polymorphism of dextromethorphan oxidation in a French population

Genetically-controlled drug oxidation capacity was studied using dextromethorphan, an anti-tussive drug, as the test compound in 103 healthy white French subjects (61 males and 42 females). Phenotyping was performed using the metabolic ratio (MR) calculated as MR = 0-10 h urinary output of dextromethorphan/0-10 h urinary output of dextrorphan, after oral administration of 40 mg (113.6 mumol) of dextromethorphan hydrobromide. The log MR was bimodally distributed: 99 subjects (96.1%) were phenotyped as extensive metabolizers; they had a log MR between -3.1 and -1.1, a urinary output of dextromethorphan below 5 mumol 10 h-1 and a urinary output of dextrorphan above 20 mumol 10 h-1. Four subjects (3.9%) were phenotyped as poor metabolizers; they had a log MR between -0.5 and +0.7, a urinary output of dextromethorphan above 5 mumol 10 h-1 and a urinary out of dextrorphan below 20 mumol 10 h-1.