Steady-state bioavailability of dexbrompheniramine and pseudoephedrine from a repeat-action combination tablet

The steady-state bioavailabilities of dexbrompheniramine and pseudoephedrine were evaluated following multiple-dose administrations of a repeat-action combination tablet containing 6 mg of dexbrompheniramine maleate with 120 mg of pseudoephedrine sulfate every 12 h for 7 d compared with reference standards. The reference standards used in this study were concomitant administration of conventional 2-mg dexbrompheniramine maleate tablets every 4 h and 120-mg pseudoephedrine sulfate repeat-action tablets every 12 h, each for 7 d. Twelve healthy adult male volunteers completed this randomized two-way crossover study. Blood samples for subsequent assay were obtained at frequent time intervals throughout each 7-d dosing phase. Sensitive and specific gas-liquid chromatographic methods were used for the determination of dexbrompheniramine and pseudoephedrine in plasma. Based on the plasma levels, the times to reach steady state were determined. In addition, the major bioavailability parameters (Cmin, Cmax, tmax, and AUC) for days 6 and 7 of dosing were determined and statistically evaluated. The results of this study demonstrate that, at steady state, the repeat-action combination tablet and concomitant administration of the reference standards are bioequivalent.