Validated HPLC method for determination of temozolomide in human plasma.

The aim of the study was to develop a bioanalytical method for the determination of temozolomide (TMZ) in human plasma. Plasma concentration of TMZ was determined on a C18 column after liquid-liquid extraction. Isocratic elution was applied with the mixture of aqueous acetic acid and methanol. Theophylline was used as the internal standard. To prevent chemical degradation of TMZ at physiological pH, plasma samples were acidified to pH < 3. All validation parameters met the acceptance criteria. Calibration curve, prepared using freshly spiked plasma samples, was linear within the range of 0.10-20.00 microg/mL. The method was found to be sufficiently accurate and precise over the studied range of concentrations. TMZ was stable in the acidified plasma samples for at least 50 days at < or = -14 degrees C and < or = -65 degrees C. The method recovery of TMZ from human plasma was consistent and ranged 37.1-41.1%. The developed method is suitable for pharmacokinetic studies in humans after oral administration of TMZ.