A highly sensitive LC-MS/MS method for determination of ketoconazole in human plasma: Application to a clinical study of the exposure to ketoconazole in patients after topical administration.

A simple, rapid and highly sensitive LC-MS/MS method was developed and validated for the determination of ketoconazole in human plasma. Sample preparation was accomplished through a single step liquid-liquid extraction by ethyl acetate. The chromatography separation was carried out on a Hedera CN (150mm×2.1mm, 5μm) column with isocratic elution using acetonitrile and 10mM ammonium acetate containing 0.1% formic acid (45:55, v/v) as the mobile phase. The flow rate was 0.5mL/min. Detection was performed in the positive ion electrospray ionization mode using multiple reaction monitoring of the transitions of 531.2→489.3 and 286.1→217.1 for ketoconazole and letrozole (the internal standard), respectively. The method exhibited good linearity over the concentration range of 0.01-12ng/mL for ketoconazole. The intra- and inter-batch precision and accuracy of ketoconazole were all within the acceptable criteria. The method was successfully applied to a clinical study of the exposure to ketoconazole in Chinese seborrheic dermatitis patients after topical administration of two ketoconazole formulations of foam and lotion, respectively. The study results showed that there was little systemic absorption of ketoconazole in patients for the two formulations, and the ketoconazole foam and lotion are safe therapeutic drugs for seborrheic dermatitis patients.