Abstract
Fexofenadine, ($\pm$)-4-1-hydroxy-4-{4-(hydroxydiphenylmethyl)-1-piperidinyl}-butyl-a,a-dimethyl benzeneacetic acid, is a selective histamine $H_1$ receptor antagonist, and is clinically effective in the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria as a first-line therapeutic agent. The purpose of the present study was to evaluate the bioequivalence of two fexofenadine hydrochloride tablets, $Allegra^{(R)}$ (Handok Pharmaceuticals Co., Ltd.) and Alecort (Samchundang Pharmaceutical Co., Ltd.), according to the guidelines of the Korea Food and Drug Administration (KFDA). The release of fexofenadine from the two fexofenadine hydrochloride formulations in vitro was tested using KP VIII Apparatus II method with various dissolution media. Twenty six healthy male subjects, 25.62$\pm$3.35 years in age and 70.05$\pm$11.71 kg in body weight, were divided into two groups and a randomized 2$\times$2 cross-over study was employed. After a single tablet containing 120 mg as fexofenadine hydrochloride was orally administered, blood samples were taken at predetermined time intervals and the concentrations of fexofenadine in serum were determined using HPLC with fluorescence detector. The dissolution profiles of two formulations were similar in all tested dissolution media. The harmacokinetic parameters such as $AUC_t$, $C_{max}$ and $T_{max}$ were calculated, and ANOVA test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_t$, $C_{max}$ and untransformed $T_{max}$. The results showed that the differences between two formulations based on the reference drug, $Allegra^{(R)}$, were -1.37, 5.22 and 16.50% for $AUC_t$, $C_{max}$ and $T_{max}$, respectively. There were no sequence effects between two formulations in these parameters. The 90% confidence intervals using logarithmically transformed data were within the acceptance range of log 0.8 to log 1.25 (e.g., log 0.83$\sim$log 1.08 and log 0.81$\sim$log 1.03 for $AUC_t$ and $C_{max}$, respectively). Thus, the criteria of the KFDA bioequivalence guideline were satisfied, indicating Alecort tablet was bioequivalent to $Allegra^{(R)}$ tablet.
