Determination of ampicillin in human plasma by solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) and its use in bioequivalence studies.

A simple, fast, sensitive and selective solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method for the quantitative analysis of ampicillin (CAS 69-53-4) in human plasma was developed using amoxicillin as internal standard, and sample extraction by solid-phase extraction (SPE). Extracts were separated by reversed-phase C18 with aqueous mobile phase (acetonitrile, 80:20, v/v) with 0.1% formic acid. The method was validated and successfully applied in a bioequivalence study of capsules 500 mg of ampicillin. Using a short running time of 2.5 min, the lower limit of quantification (LLOQ) for obtained ampicillin was 0.1 microg/ml for a plasma sample of 250 microl and a recovery of 94.38% +/- 4.05. Bioequivalence between the products was determined by calculating 90% confidence intervals (CI) for the ratio of Cmax, AUC0-t and AUC0-inf values for the test and reference products, which were within the 0.80-1.25 interval proposed by FDA and EMEA. It is concluded that the two formulations are bioequivalent in their rate and extent of absorption, and thus, may be used interchangeably.

Atenolol quantification in human plasma by high-performance liquid chromatography: application to bioequivalence study.

An accurate, precise, and sensitive high-performance liquid chromatography (HPLC) assay was developed for the determination of atenolol in human plasma samples to compare the bioavailability of 2 atenolol tablet (50 mg) formulations in 24 volunteers of both sexes. The study had an open, randomized, 2-period crossover design with a 1-week washout period. Plasma samples were obtained over a 24-hour interval. Atenolol concentrations were analyzed by combined reversed phase liquid chromatography and fluorescence detection (lambda(EX) = 258 nm, lambda(EM) = 300 nm). From the atenolol plasma concentration versus time curves, the following pharmacokinetic parameters were obtained: AUC(0-24h), AUC(0- infinity ), and C(max). The geometric mean of test/reference 50-mg tablets individual percent ratio was 102.2% for AUC(0-24h), and 101.6% for C(max). The 90% confidence intervals (CI) were 100.2% to 105.4% and 100.9% to 103.5%, respectively. Since the 90% CI for both C(max) and AUC(0-24h) were within the 80% to 125% interval proposed by the Food and Drug Administration, it was concluded that atenolol (50-mg tablets) test formulation was bioequivalent to the reference formulation, with regard to both the rate and extent of absorption.