The Bioequivalence of Doxazosin Slow Release Tablets: A Pilot Study

Generic drugs used instead of originator products have to undergo obligatory bioequivalence studies before being approved on the market. The study was designed to validate a chromatographic and extraction method for the determination of doxazosin in human plasma and to carry out a pilot study on the bioequivalence between the test product, doxazosin mesylate 8mg slow release tablets and the reference product, Cardura®XL 8mg tablets. The study was determined in two healthy individuals after one single dose in a cross over study with a two week wash out period. A simple and sensitive liquid-liquid extraction method was validated for the quantification of doxazosin in human plasma using reversed-phase high performance liquid chromatography with fluorescence detection. The bioequivalence study showed significant variance between the generic and reference product and although further studies using larger number of individuals is recommended, such pilot studies gives an indication on the systemic exposure pattern and are beneficial to manufacturers as indicators of their products¿ performance in vivo before embarking on full scale bioequivalence trials.