Pharmacokinetics and bioequivalence evaluation of two different atorvastatin calcium 10-mg tablets: A single-dose, randomized-sequence, open-label, two-period crossover study in healthy fasted Chinese adult males

Background: Atorvastatin calcium is a 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor indicated for the prevention of cardiovascular disease and for the treatment of dyslipidemia. Information on the pharmacokinetics of atorvastatin in a Chinese population is lacking, and regulatory requirements necessitate a bioequivalence study for the marketing of a generic product in China.Objective: The aim of the present study was to assess the pharmacokinetics and bioequivalence of a test and branded reference formulation of atorvastatin calcium 10-mg tablets in healthy fasted Chinese male volunteers.Methods: This was a single-dose, randomized-sequence, open-label, 2-period crossover study with a 2-week washout period between doses. Healthy Chinese males were randomly assigned to receive 20 mg of either the test or reference formulation, and 13 blood samples were obtained over a 48-hour interval. Plasma concentrations of parent atorvastatin and ortho-hydroxy-atorvastatin (primary active metabolite) were simultaneously determined using a validated liquid chromatography-isotopic dilution mass spectrometry method. Pharmacokinetic parameters, including Cmax, Tmax, t½, AUC0−t, and AUC0−∞), were calculated. The 2 formulations were to be considered bioequivalent if 90% CIs for the logtransformed ratios of AUC and Cmax of atorvastatin were within the predetermined bioequivalence range (0.80–1.25 for AUC and 0.70–1.43 for Cmax) as established by the State Food and Drug Administration of China. Tolerability was evaluated throughout the study by vital signs monitoring, physical examinations, 12-lead ECGs, and subject interviews on adverse events (AEs).Results: A total of 66 subjects were assessed for inclusion; 20 were excluded prior to study initiation. Of the 46 healthy subjects (mean [SD] age, 24.1 [2.5] years; height, 170.8 [5.1] cm; weight, 64.6 [6.4] kg; body mass index (BMI), 22.1 [1.7] kg/m2) who completed the study, 45 subjects (mean [SD] age, 24.1 [2.5] years; height, 171.1 [4.9] cm; weight, 64.8 [6.3] kg; BMI, 22.1 [1.7] kg/m2) were included in the pharmacokinetic and bioequivalence analyses; 1 subject was excluded from these analyses because he mistakenly received the same formulation in both periods. No period or sequence effect was observed. The mean values of Cmax, AUC0−t, and AUC0−∞) for the test and reference formulations of atorvastatin (8.78 and 10.76 ng/mL, 38.22 and 40.02 ng/mL/h, 42.73 and 44.51 ng/mL/h, respectively) and ortho-hydroxy-atorvastatin (5.78 and 5.77 ng/mL, 47.32 and 48.47 ng/mL/h, 52.36 and 53.14 ng/mL/h) were not significantly different. The 90% CIs for natural log-transformed ratios of Cmax, AUC0−t, and AUC0−∞) of both atorvastatin (0.73–0.91, 0.92–1.02, and 0.91–1.01, respectively) and ortho-hydroxy-atorvastatin (0.83–1.05, 0.92–1.02, and 0.93–1.02) were within the bioequivalence acceptance limits. Three subjects (6.5%) reported a total of 4 mild AEs (1 abdominal discomfort and 3 venipuncture syncope), which were not considered to be associated with administration of the study drug.Conclusions: This single-dose (20 mg) study found that the test and reference formulations of atorvastatin calcium 10-mg tablet met the regulatory definition for assuming bioequivalence in these healthy fasted Chinese male volunteers. Both formulations were generally well tolerated in the population studied. Chinese National Registry Code: 2007L02512.