Comparative bioavailability study with two sodium valproate tablet formulations administered under fasting conditions in healthy subjects.

AIM: To assess the bioequivalence of two sodium valproate formulations in healthy subjects of both sexes. MATERIALS AND METHODS: The study was conducted using an open, randomized, two-period crossover design with a 2-week washout interval. Plasma samples were obtained over a 96-hour period. Plasma concentrations of valproate were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC/MS) with negative ion electrospray ionization. From the sodium valproate plasma concentration vs. time curves, the following pharmacokinetic parameters were obtained Cmax, AUC, tmax, Ke, and T1/2. RESULTS: The geometric mean with corresponding 90% confidence interval for test/reference percent ratios were 104.43% (90% CI 100.42 - 108.61%) for Cmax, 98.11% (90% CI = 94.66 - 101.70%) for AUClast, and 96.71% (90% CI = 92.97 - 100.60%) for AUC0-inf. CONCLUSION: Since the 90% CI for Cmax and AUClast ratios were all inside the 80 - 125% interval proposed by the US Food and Drug Administration Agency (FDA), it was concluded that the new sodium valproate formulation (epilenil 500-mg coated tablet) without food elaborated by Biolab Sanus Farmaceutica Ltda is bioequivalent to depakene formulation for both the rate and the extent of absorption.

Quantification of 6-nitrodopamine in Krebs-Henseleit's solution by LC-MS/MS for the assessment of its basal release from Chelonoidis carbonaria aortae in vitro.

In this study, the development and validation of a method for quantification of 6-nitrodopamine in Krebs-Henseleit's solution by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with positive ion electrospray ionization is described. Aortic rings taken from tortoise were either denuded or left with endothelium intact (15 mm, N = 6) and were incubated for 30 min in 5 mL Krebs-Henseleit's solution in an organ bath. Solid phase extraction (SPE) was performed for aliquots of 1 mL of the supernatant. The separation of 6-nitrodopamine was obtained on a 150 mm × 3 mm Shim-pack GIST-HP C18 column, using 75% of mobile phase A consisted of deionized water with 0.1% formic acid (v/v) and 25% of mobile phase B consisted of acetonitrile/deionized water (50/50, v/v) + 0.1% formic acid at a flow rate of 350 µL/min in an isocratic mode. The method was linear over the concentration range of 0.1-20 ng/mL. The method was sensitive, precise and accurate for the assessment of the basal release of 6-nitrodopamine from Chelonoidis carbonaria aortae in vitro. The mean ± SEM concentrations of 6-nitrodopamine released from endothelium-intact and endothelium-denuded aortae were 0.44 ± 0.06 ng/mL and 0.18 ± 0.05 ng/mL, respectively. These results indicate that tortoise's aortae display a basal endothelium-derived 6-nitrodopamine release.