Carboxyterfenadine antacid interaction monitoring by UV spectrophotometry and RP-HPLC techniques

Carboxyterfenadine, a primary metabolite of terfenadine, a second generation antihistaminic compound was introduced in therapy as a successor of terfenadine due to its cardiac arrhythmia. There are number of drug interactions of fexofenadine with erythromycin, ketoconazole and alike reported in the literature. In this paper, fexofenadine antacid interaction has been studied in presence of sodium bicarbonate, megaldrate, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium trisilicate, simethicone (dimethylpolysiloxane) and calcium hydroxide by UV–Vis spectrophotometer and high performance liquid chromatography (HPLC). These in vitro fexofenadine–antacid interactions were carried out in simulated gastric and intestinal juices and in buffer of pH 7.4 (simulating blood pH) on BP 2005 dissolution apparatus. The results show non-concordant availability of fexofenadine envisaged due to formation of unstable charge transfer complexes.