HPLC analysis of the antifungal agent posaconazole in patients with haematological diseases

Posaconazole is a new antifungal drug used in prophylaxis and therapy of fungal infections in patients with immunodeficiency. In the clinical development, posaconazole exhibits variable oral bioavailability. Hence drug monitoring is recommended. For this purpose, a rapid and a convenient high-performance liquid chromatography (HPLC) method has been developed. To 200 mu l serum, 50 mu l internal standard (itraconazole) was added. After precipitation of the proteins with acetonitrile, the clear supernatant was evaporated in a centrifugal evaporator, and the residue was dissolved in the HPLC elution. Separation was done on a chromatography performed by injecting a 50 mu l aliquot of the resuspended sample onto a Multohyp C18 BDS column (250 x 4 mm). Column temperature was maintained at 50 degrees C. The flow rate was 1 ml min(-1). Retention time of posaconazole was about 9 min and those of itraconazole was 17 min. The limit of quantification was 50 mu g l(-1) and the limit of detection about 10 mu g l(-1). Until now the concentration of posaconazole was measured in 14 patients (64 samples). After a daily dosage of 600-800 mg posaconazole the serum concentrations varied between 100 and 3000 mu g l(-1) (582 +/- 579 mu g l(-1)). Oral bioavailability was especially low in patients with cytostatic therapy and/or bone marrow transplantation. Further studies are needed to establish the therapeutic range of the posaconazole concentrations.