A comparison of 4β-hydroxycholesterol : cholesterol and 6β-hydroxycortisol : cortisol as markers of CYP3A4 induction.

Aim: To compare plasma 4β-hydroxycholesterol : cholesterol with urinary 6β-hydroxycortisol : cortisol as markers of cytochrome P4503A4 activity before and after treatment with rifampicin for 2 weeks.

Method: 6β-hydroxycortisol and cortisol were determined by liquid chromatography tandem mass spectrometry and 4β-hydroxycholesterol was determined by gas chromatography-mass spectrometry in three groups of healthy volunteers.

Results: Induction ratios for 6β-hydroxycortisol : cortisol were 1.