A rapid, sensitive and specific analytical method was developed and validated to quantify gabapentin in human plasma using acetaminophen as an internal standard. The method employs a single plasma protein precipitation. The analytes are chromatographed on a C4 reversed-phase chromatographic column and analyzed by mass spectrometry in the multiple reaction monitoring (MRM) mode. The method has a chromatographic run time of 4 min and a linear calibration curve over the range 50-10 000 ng x ml(-1) (r > 0.999). The between-run precision, based on the relative standard deviation for replicate quality controls, was < or = 4.8 % (200 ng x ml(-1)), 6.0% (1000 ng x ml(-1)) and 4.4% (5000 ng x ml(-1)). The between-run accuracy was +/-2.6, 4.4 and 0.5% for the above-mentioned concentrations, respectively. This method was employed in a bioequivalence study of two gabentin capsule formulations (Progresse from Biosintética, Brazil, as a test formulation, and Neurotin from Parke-Davis, as a reference formulation) in 24 healthy volunteers of both sexes who received a single 300 mg dose of each formulation. The study was conducted using an open, randomized, two-period crossover design with a 7-day washout interval. The 90% confidence interval (CI) of the individual ratio geometric mean for Progresse/Neurotin was 87.9-115.6% for AUC(0-36 h) and 88.6-111.7% for Cmax. Since both 90% CI for AUC(0-36 h) and Cmax were included in the 80-125% interval proposed by the US Food and Drug Administration, Progresse was considered bioequivalent to Neurotin according to both the rate and extent of absorption.

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Objective: The aim was to assess the comparative bioavailability of two formulations (200 mg tablet) of amiodarone (CAS 19774-82-4) in healthy volunteers of both sexes, with and without food. Methods: The study was conducted using an open, randomized, two-period crossover design with a 3-week washout interval, in two groups, with and without food. Plasma samples were obtained for up to 240 h post dose. Plasma amiodarone concentrations were analyzed by liquid chro-matography coupled to tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using multiple reactions monitoring (MRM). From the amiodarone plasma concentration vs. time curves, the following pharmacoki-netic parameters were obtained, with and without food: AUClast, AUCinf, AU C0-240h, AUC0-72h and Cmax. Results: The limit of quantification was 1 ng/mL for plasma amiodarone analysis. The geometric mean and 90 % confidence interval CI of Test/Reference percent ratios were, without and with food, respectively: 107.61 (92.73?124.89) and 100.6 (94.1?107.5) for Cmax, 107.05 (95.88?119.51) and 100.2 (96.0?104.7) for AUClast, 107.27 (95.78?120.15) and 100.8 (97.0?104.8) for AUC0-72h , 106.76 (95.84? 118.94) and 100.2 (96.0?104.7) for AUC0-240h and AUCinf 105.15 (94.18?117.41) and 100.7 (96.6?105.0). Conclusion: Since the 90 % CI for AUC0-72, and Cmax ratios were within the 80?125 % interval proposed by the US FDA, it was concluded that the amio-darone 200 mg tablet (test formulation) with and without food was bioequivalent to the reference 200 mg tablet for both the rate and extent of absorption.

Since the 90% CI for AUClast and Cmax ratios were within the 80-125% interval proposed by the US FDA, it was concluded that cefuroxime axetil (test formulation, 250 mg/5 mL suspension) was bioequivalent to a reference formulation under fed conditions, for both the rate and extent of absorption.