Bioavailability of d-pseudoephedrine and azatadine from a repeat action tablet formulation.

The objective of this study was to compare in man the bioavailability of d-pseudoephedrine and azatadine from a repeat action tablet formulation and from conventional tablets. The repeat action tablet, containing 1 mg of azatadine maleate in the coat, and 60 mg of d-pseudoephedrine sulfate in both the coat and the core, was given at 0 hour. A conventional tablet of 60 mg of d-pseudoephedrine sulfate was given at 0 and 4 hours and a conventional tablet of 1 mg of azatadine maleate was given at 0 hour. The plasma levels of d-pseudoephedrine were measured by gas-liquid chromatography and the amount of azatadine in the urine was determined by a mass fragmentographic procedure. The results showed that there were no statistically significant differences in the measured bioavailability parameters (area under plasma concentrations-time curve, maximum plasma concentration and time to reach maximum plasma concentration) for pseudoephedrine from repeat action tablets and conventional d-pseudoephedrine sulfate tablets; neither was there any statistically significant difference in the cumulative urinary excretion of azatadine from the repeat action tablets and conventional azatadine maleate tablets (p less than 0.10). These data clearly demonstrate the bioequivalence of the repeat action tablets and the conventional tablets of d-pseudoephedrine and azatadine.