• Journal of Pharmaceutical Investigation
• /
• v.30 no.1
• /
• pp.61-65
• /
• 2000

Doxazosin, a postsynaptic selective ${\alpha}1-adrenoceptor$ antagonist, is a potent antihypertensive agent which reduces peripheral resistance and blood pressure by vasodilatation of peripheral vessels. It is also used in the treatment of urinary obstruction by benign prostatic hypertrophy. The purpose of the present study was to evaluate the bioequivalence of two doxazosin tablets, $Cardura^{TM}$ (Pfizer Korea Ltd.) and $Cardil^{TM};$ (Kyungdong Pharmaceutical Co., Ltd.), according to the guidelines of Korea Food and Drug Administration (KFDA). Sixteen normal male volunteers, $24.19{\pm}2.48$ years in age and $62.41{\pm}6.66$ kg in body weight, were divided into two groups and a randomized $2{\times}2$ cross-over study was employed. After one tablet containing 2 mg of doxazosin was orally administered, blood was taken at predetermined time intervals and the concentrations of doxazosin in serum were determined with an HPLC method using spectrofluorometric detector. Pharmacokinetic parameters such as $AUC_t,\;C_{max}\;and\;T_{max}$ were calculated and ANOVA test was utilized for the statistical analysis of the parameters. The results showed that the differences in $AUC_t,\;C_{max}\;and\;T_{max}$ between two tablets were -1.54%, -1.51 % and 3.42%, respectively, when calculated against the $Cardura^{TM}$ tablet. The powers $(1-{\beta})$ for $AUC_t,\;C_{max}\;and\;T_{max}$ were all more than 99.00%. Minimum detectable differences $(\Delta)$ at ${\alpha}=0.05\;and\;1-{\beta}=0.8$ were all less than 20% (e.g., 12.73%, 12.84% and 13.01% for $AUC_t,\;C_{max}\;and\;T_{max}$, respectively). The 90% confidence intervals were all within :${\pm}20%$ (e.g., $-8.97{\sim}5.90,\;-9.01{\sim}6.00\;and\;-4.16{\sim}11.05\;for\;AUC_t,\;C_{max}\;and\;T_{max},\;respectively)$. All of the above para- meters met the criteria of KFDA for bioequivalence, indicating that $Cardil^{TM}$ tablet is bioequivalent to $Cardura^{TM}$ tablet.