Acta Pharmacologica Sinica 2005 Sep; 26 (9): 1145-1152; doi: 10.1111/j.1745-7254.2005.00187.x

Aim: To investigate the influence of dosage forms on the pharmacokinetics of daidzein and its main metabolite daidzein-7-O-glucuronide in Wistar rats.

Methods: After administration of two typical dosage forms (daidzein solution and suspension), the concentrations of daidzein and daidzein-7-O-glucuronide were determined by an LC-MS-MS method. The pharmacokinetic parameters were calculated and analyzed statistically using the Student's t-test.

Results: Absorption of daidzein after administration of daidzein solution (t_max=0.46 h) was more rapid than that of the suspension (t_max=5.00 h). The peak plasma concentrations of daidzein after administration of daidzein solution and suspension were 601.1 µg/L and 127.3 µg/L, respectively, and those of daidzein-7-O-glucuronide were 3000 µg/L and 192.6 µg/L, respectively. The absolute bioavailabilities of free daidzein in rats after administration of daidzein solution and suspension were 12.8% and 6.1%, respectively, which were calculated to be 47.0% and 12.2%, respectively, in the form of total daidzein (free plus conjugated daidzein).

Conclusion: Absorption of daidzein solution was better than absorption of suspension (P<0.05).

Keywords: daidzein; daidzein-7-O-glucuronide; influence; dosage forms; pharmacokinetics; rats