Pharmacodynamic bioequivalence: evaluation of different brands of terfenadine hydrochloride

Terfenadine is a selective histamine H1 receptor antagonist which binds preferentially to peripheral receptors in vivo and is devoid of central nervous system depressant activity and thus has an improved adverse effect profile (1). Hence, terfenadine may be considered to be a first line agent in the treatment of allergic rhinitis and chronic urticaria. In man terfenadine is rapidly absorbed following a single oral dose and a peak terfenadine plasma concentration is reached within 1-2 hr after the drug administration (2). The present study was carried out to compare the bioequivalence of two terfenadine hydrochloride preparations marketed by Kopran Chem. Co. and Marrel Dow U.K. (Triludan) by evaluating their ability to inhibit the skin reaction to intradermally injected histamine (3).