Steady-state pharmacokinetic properties of tamsulosin in healthy male volunteers

Background: To evaluate the pharmacokinetic properties of daily oral doses of tamsulosin administered to fasted healthy Korean male volunteers for 5 days. Methods: In a randomized, open-label, multiple-dose, two-period, crossover study, all 44 subjects were randomly assigned in a 1:1 ratio to receive a newly developed generic capsule formulation (test) or a branded capsule formulation (reference) of tamsulosin 0.2 mg, followed by a 10-day washout period and administration of the other formulation. Plasma concentrations of tamsulosin were assessed after administration of five-day multiple doses, using HPLC-MS/MS. Clinical and laboratory adverse events (AE) were assessed. Results: The mean (SD) pharmacokinetic properties with the test and reference formulations were as follows: C_{ss, max}, 9.0 (2.9) and 8.4 (2.6) ng/mL, respectively; median (range) t_max, 4 (2-6) and 5 (2-7) hours; AUC_τ, 93.7 (31.5) and 88.2 (29.3) ng × h/mL; and t_1/2, 9.5 (2.6) and 10.0 (2.7) hours. The volume of distribution and clearance after oral administration of tamsulosin were 0.5 L/kg, and 0.04 L/h/kg, respectively. The accumulation ratios for 0.2 mg once-daily dosing regimen were 1.2. The 90% CIs of the geometric mean ratios for the log-transformed AUC_τ (1.005-1.131) and C_{ss, max} (1.000-1.136) values were within the acceptable range for bioequivalence. No serious AE was reported during the study. Both formulations were well tolerated. Conclusion: The results demonstrate that the C_{ss, max} and AUC_τ values in the fasted subjects were higher than those in the fed from other study, with a shorter t_max values.