Simultaneous determination of stavudine and lamivudine in human plasma by high performance liquid chromatography and its application to a bioavailability study.

A high performance liquid chromatographic method with UV detection was developed and validated for simultaneous determination of stavudine and lamivudine in human plasma using solid-phase extraction for sample clean-up. Zidovudine was used as an internal standard. Separation was performed on a C18 column by gradient elution with a mobile phase of 10 mM acetate buffer pH 6.5 and acetonitrile. The UV detection was set at 265 nm. The method proved to be specific, accurate, precise and linear over the concentration ranges of 50-3000 ng/ml for stavudine and 50-5000 ng/ml for lamivudine with correlation coefficients always > 0.996 for both drugs. The intra-day and inter-day precision and accuracy were less than 9.2% for both analytes. The absolute recoveries of both compounds ranged from 93.3 to 97.5%. The method was successfully applied to a bioavailability study of a combined tablet formulation containing 30 mg of stavudine and 150 mg of lamivudine compared with each reference formulation concurrently administered in 26 healthy Thai male volunteers.

Validated LC-MS-MS method for the determination of gabapentin in human plasma: application to a bioequivalence study.

A simple and rapid liquid chromatography-tandem mass spectrometric method is developed and validated for the determination of gabapentin in human plasma. Metformin is used as an internal standard. The method utilizes protein precipitation with acetonitrile followed by separation on a C(8) column using 10 mM ammonium formate buffer pH 3.0 and acetonitrile as mobile phase. Detection was performed on a quadrupole mass spectrometer using an electrospray ionization interface in selected reaction monitoring mode. The method proves to be specific, sensitive, accurate, precise, and linear over the concentration range of 50-5000 ng/mL with correlation coefficients greater than 0.99. The lower limit of quantification for gabapentin is 50 ng/mL using a 200-microL plasma sample. Intra- and inter-day precisions are less than 8.4% whereas accuracies are within 10.2%. The method is successfully applied to a bioequivalence study of gabapentin in 24 healthy volunteers.

Validated HPLC method for the determination of fluconazole in human plasma.

A high-performance liquid chromatographic assay with UV detection was developed for the determination of fluconazole in human plasma. The method utilized solid-phase extraction for sample clean-up. The separation was performed on a C18 column by isocratic elution with a mobile phase of 10 mM acetate buffer at pH 5.0 and methanol and UV detection at 210 nm. Validation was performed according to the current recommendations of the USFDA bioanalytical method validation guidance. The method proved to be specific, accurate, precise and linear between 200 and 10,000 ng/mL with correlation coefficients greater than 0.999. The coefficient of variation was within 11% and relative deviation was less than 10%.