The effect of induction of CYP3A4 by St John's wort on ambrisentan plasma pharmacokinetics in volunteers of known CYP2C19 genotype.

To evaluate the impact of CYP2C19 polymorphisms on ambrisentan exposure and to assess its modification by St. John's wort (SJW), 20 healthy volunteers (10 CYP2C19 extensive, four poor and six ultrarapid metabolizers) received therapeutic doses of ambrisentan (5 mg qd po) for 20 days and concomitantly SJW (300 mg tid po) for the last 10 days. To quantify changes of CYP3A4 activity, midazolam (3 mg po) as a probe drug was used.

The influence of a carbon layer deposited on a zirconia surface on the retention of polar analytes in an organic rich mobile phase.

Hydrophilic interaction liquid chromatography (HILIC) represents a modern MS-friendly approach to the analysis of polar compounds. To date especially silica-based HILIC stationary phases are utilized. Recently the papers concerning retention of polar analytes on unmodified titania and zirconia as well as a polybutadiene modified zirconia stationary phase under HILIC conditions have been published.