Development and validation of a high-performance liquid chromatography assay for posaconazole utilizing solid-phase extraction

Background: Posaconazole is a new broad-spectrum triazole antifungal drug that is used in prophylaxis and therapy of opportunistic fungal infections in immunocompromised patients. Up to now, it is available as an oral suspension only. Due to variable systemic availability known from other azoles, such as itraconazole, it is important to measure blood levels, especially in patients undergoing abdominal surgery which may influence the intestinal resorption. Methods: A sensitive and selective high-performance liquid chromatography method for the precise determination of posaconazole and the internal standard clotrimazole in human plasma was developed and validated. Samples were extracted using solid-phase extraction and separated on a reversed-phase C8 column (150x4.6 mm, 5 mu m) using phosphate buffer (pH 6.7, 0.04 M): acetonitrile: methanol (43:49:8, v/v/v) as mobile phase. UV detection was performed at 260 nm. Results: This method showed that a lower limit of quantification was 50 ng/mL and the limit of detection 3 ng/mL. Linearity was tested in the range from 50 to 5000 ng/mL (r(2) = 0.9998). Mean recovery was 86%. Conclusions: The method proved to be a useful tool for therapeutic drug monitoring. It is specific, precise and showed excellent reproducibility as well as a favourable accuracy. Clin Chem Lab Med 2008; 46:1747-51.