Journal of Bioequivalence & Bioavailability

Abstract

Pharmacokinetic and Pharmacodynamic Study of Terazosin in Healthy Chinese Volunteers: Significant Hysteresis Phenomenon

Guifen Qiang, Man Yang, Yanan Zhang, Man Liu, Dan Zhang, Guocai Wang, Jing Han, Xue Xiao, Zhenlong Wang and Huichen Liu

Aim: The present study investigated the correlation between plasma concentration and antihypertensive effect of terazosin in healthy Chinese volunteers. Methods: A randomized, single-dose pharmacokinetic study of 2 mg terazosin hydrochloride tablet was conducted in healthy Chinese male subjects. Supine blood pressure and heart rate were measured before and after dosing, using cardiogram monitor. Serial blood samples were collected and plasma concentrations of terazosin were quantified by high performance liquid chromatography (HPLC) with a fluorescence detector. Non-compartmental pharmacokinetic analysis was applied to plasma concentrations. Results: Plasma concentration of terazosin reached to peak concentration at 0.89±0.62 hours (T max ), and then decreased with half-life value of 10.21±1.41 hours. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreased from 0.25 hours till 24 hours after dosing. The maximum decrease of 8.5±5.3 mmHg (7.78%) in SBP ( P <0.05) and 12.9±6.0 mmHg (19.82%) in DBP ( P <0.001) occurred at 8 hours after dosing with a lagging time of 7 hours than T max , different from 1.2-1.8 hours of lagging time in healthy Spanish subjects. The heart rate increased from 0.25 hours till 24 hours with the maximum increase of 14.3±7.8 beats/min (23.85%) at 6 hours after dosing. Conclusion: The findings suggested that terazosin had a significant hysteresis phenomenon of antihypertensive effect behind plasma concentration of terazosin in healthy Chinese subjects, as was different from other racial subjects