Influence of St. John's wort on the steady-state pharmacokinetics and metabolism of bosentan.

Objective: We assessed the effect of St. John's wort (SJW) on bosentan pharmacokinetics at steady-state in different CYP2C9 genotypes in healthy volunteers.

Methods: Nine healthy extensive metabolizers of CYP2C9 and 4 poor metabolizers received therapeutic doses of bosentan (125 mg q.