Development and validation of a high-performance liquid chromatography/tandem mass spectrometry method for the determination of artemether and its active metabolite dihydroartemisinin in human plasma.

To study the pharmacokinetic profile of artemether in children and in the context of antiviral drugs for HIV infected patients co-infected with malaria, an LC-MS/MS method was developed and validated to simultaneously determine artemether and its metabolite dihydroartemisinin in human plasma. Using artemisinin as the internal standard, 0.5 mL samples were processed with solid phase extraction (Waters Oasis HLB column), the elutes were directly injected onto a C18 LC column (Waters, Symmetry, 150 mm x 4.6 mm, 5 microm). Mass detection utilized ESI+ as the ionization mode and MRM as the quantitation mode. In respect to the low ionization capacity of artemether, ammonium formate was added to the LC mobile phase to facilitate ionization (M+NH4+). The calibration range was 2-200 ng/mL. The recovery was 73-81% for artemether and 90-99% for dihydroartemisinin. The validated method was applied to analysis of clinical samples with results in good agreement with an existing method.