A sensitive high-performance liquid chromatography-positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 408-235 for sitagliptin and m/z 310-148 for the internal standard. The assay exhibited a linear dynamic range of 0.1-250 ng/mL for sitagliptin in human plasma. The lower limit of quantification was 0.1 ng/mL with a relative standard deviation of less than 6%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic studies.

A high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method for the simultaneous quantification of efavirenz, emtricitabine and tenofovir was developed and validated with 100 microL human plasma. Following solid-phase extraction, the analytes were separated using a gradient mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H]+ ions, m/z 316 to 168 for efavirenz, m/z 248-130 for emtricitabine and m/z 288-176 for tenofovir, m/z 482-258 for rosuvastatin (IS), m/z 260-116 for propranolol (IS). The method exhibited a 100-fold linear dynamic range for all the three analytes in human plasma (20-2000, 2-200 and 20-2000 ng/mL for efavirenz, emtricitabine and tenofovir respectively). The lower limit of quantification was 2 ng/mL for emtricitabine and 20 ng/mL for both efavirenz and tenofovir with a relative standard deviation of less than 11%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 4 min for each sample made it possible to analyze more than 250 human plasma samples per day. The method is precise and sensitive enough for its intended purpose. The method is also successfully applied to quantify efavirenz, emtricitabine and tenofovir concentrations in a rodent pharmacokinetic study.

No abstract

A rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of fexofenadine in human plasma using mosapride as internal standard. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 502/466 for fexofenadine and m/z 422/198 for the IS. The method exhibited a linear dynamic range of 1-500 ng/mL for fexofenadine in human plasma. The lower limit of quantification was 1 ng/mL with a relative standard deviation of less than 5% for fexofenadine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 2 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

During pregnancy, the disposition of various drugs is altered due to changes in physiological condition, maternal gastrointestinal absorption, gastric secretion and motility. A fixed dose combination of antiretrovirals is commonly prescribed for the treatment of HIV infection. There is a need to understand the pharmacokinetics and placental transfer of efavirenz-emtricitabine-tenofovir in fixed dose combination during pregnancy. The pharmacokinetics and placental transfer of efavirenz-emtricitabine-tenofovir fixed dose combination was evaluated in timed pregnant and non-pregnant Sprague-Dawley rats at 30, 10, 15 mg/kg p.o., respectively. The plasma, placental tissue, amniotic fluid and fetal tissue concentrations were measured using high performance liquid chromatography combined with tandem mass spectrometric detector (LC-MS/MS). To summarize, the pharmacokinetic profile of efavirenz remained similar in the pregnant and non-pregnant rats. However, a considerable difference in the pharmacokinetics of emtricitabine and tenofovir was observed in pregnant and non-pregnant rats. Efavirenz and emtricitabine showed appreciable placental, amniotic fluid and fetal exposure compared with tenofovir. The present study suggests that a profound impact on antiretroviral pharmacokinetics was observed during pregnancy and there is a need to monitor the exposure levels of each drug when administered as a fixed dose combination during pregnancy. Further studies to explore the pharmacokinetic parameters of fixed dose antiretrovirals during the preclinical stage in a timed-pregnancy rat model are required. Such studies can help in the development of safe and effective medications with a reduced risk of perinatal transmission of HIV-1 infection.