A bioequivalence study of two memantine formulations in healthy Chinese male volunteers
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OBJECTIVE: The aim of the current study is to evaluate the bioequivalence between the test and reference formulations of memantine in a single-dose, two-period and two-sequence crossover study with a 44-day washout interval. MATERIALS AND METHODS: A total of 20 healthy Chinese male volunteers were enrolled and completed the study, after oral administration of single doses of 10 mg test and reference formulations of memantine. The blood samples were collected at different time points and memantine concentrations were determined by a fully validated HPLC-MS/MS method. The evaluated pharmacokinetic parameters (test vs. reference) including Cmax (18 ± 3.2 vs. 17.8 ± 3.4), AUC0-t (1,188.5 ± 222.2 vs. 1,170.9 ± 135.7), and AUC0-∞ (1,353.3 ± 258.6 vs. 1,291.3 ± 136.7) values were assessed for bioequivalence based on current guidelines. RESULTS: The observed pharmacokinetic parameters of memantine test drug were similar to those of the reference formulation. The 90% confidence intervals of test/reference ratios for Cmax, AUC0-t, and AUC0-∞ were within the bioequivalence acceptance range of 80 - 125%. CONCLUSION: The results obtained from the healthy Chinese subjects in this study suggests that the test formulation of memantine 10 mg tablet is bioequivalent to the reference formulation (Ebixa®10 mg tablet).
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Validation of a HPLC-ESI MS/MS method for the determination of clonidine in human plasma and its application in a bioequivalence study in Chinese healthy volunteers.

A rapid and sensitive liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method to determine clonidine in human plasma was developed and fully validated. Sample preparation was involved an one-step extraction with diethyl ether. Donepezil was employed as the internal standard (IS). Chromatographic separation was performed on a Hypersil BDS C18 column (i.d. 2.1 × 50 mm, particle size 3µm) with a mobile phase of methanol-water (containing 0.1% formic acid; 60:40, v/v) at a flow rate of 200 µL/min. The peaks were detected by mass spectrometry using the electrospray ion source in selected reaction monitoring mode. The extraction recovery was 72.53-85.25%. The method was found to be linear in a concentration range of 0.02-6.00 ng/mL and the lower limit of quantification was 0.02 ng/mL. The within- and between-batch precisions at three concentrations were 4.33-16.47 and 7.24-17.24% with accuracies of -2.47-10.91 and 1.86-10.19%, respectively. This validated method was successfully used for a bioequivalence study of two clonidine transdermal patches on healthy volunteers. The results suggested that the test formulation of clonidine patch met the regulatory criterion for bioequivalence to the reference formulation, but a larger sample size should be needed for the estimation of bioequivalence.

Bioequivalence of Oral Formulations of Anastrozole in Healthy Chinese Male Volunteers: A Randomized, Single-Dose, Two-Period, Two-Sequence Crossover Study.

Anastrozole is currently used as first-line treatment in locally advanced or metastatic breast cancer. A generic anastrozole tablet was developed to offer an alternative to the marketed tablet formulation. The aim of the current study was to evaluate the bioequivalence between the test and reference formulations of anastrozole in a single-dose, 2-period, 2-sequence crossover study with a 14-day washout interval. A total of 20 healthy male Chinese volunteers were enrolled and completed the study, after oral administration of a single dose of 1.0-mg test and reference formulations of anastrozole. The blood samples were collected at different times and were determined by a fully validated high-pressure liquid chromatography-tandem mass spectrometry method. The evaluated pharmacokinetic parameters, including Cmax , AUC0-t , and AUC0-∞ , were assessed for bioequivalence based on current guidelines. The observed pharmacokinetic parameters of anastrozole of the test drug were similar to those of the reference formulation. The 90% confidence intervals of test/reference ratios for Cmax , AUC0-t , and AUC0-∞ were within the bioequivalence acceptance range of 80%-125%. The results obtained from these healthy Chinese subjects in this study suggest that the test formulation of anastrozole 1.0-mg tablet is bioequivalent to the reference formulation (Arimidex 1.0-mg tablet).

Determination of HS270, a new histone deacetylase inhibitor, in rat plasma by LC-MS/MS--application to a preclinical pharmacokinetic study.

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and fully validated to determine HS270, a new histone deacetylase (HDAC) inhibitor, in rat plasma using SAHA as the internal standard (IS). After a single step liquid-liquid extraction with acetoacetate, analytes were subjected to LC-MS/MS analysis using positive electro-spray ionization (ESI(+)) under selected reaction monitoring mode (SRM). The chromatographic separation was achieved on a Hypurity C(18) column (50 mm × 2.1 mm, i.d., 5 µm). The MS/MS detection was conducted by monitoring the fragmentation of m/z 392.3→100.1 for HS270, m/z 265.1→232.1 for IS. The method had a chromatographic running time of 2.5 min and linear calibration curves over the concentrations of 0.5-1000 ng/mL. The recovery of the method was 70.8-82.5% and the lower limit of quantification (LLOQ) was 0.5 ng/mL. The intra- and inter-batch precisions were less than 15% for all quality control samples at concentrations of 1.0, 100.0, and 750.0 ng/mL. The validated LC-MS/MS method has successfully applied to a HS270 pharmacokinetic study after oral doses of 25, 50, 100, 200 mg/kg, and i.v. dose of 5 mg/kg to rats.