Relative bioavailability of three commercial quinidine dosage forms

Bioavailabilities of three quinidine formulations were compared. Two tablets of each dosage form were administered to 12 healthy volunteers according to a repeated Latin square design; plasma levels of unchanged and total drug were determined. Quinidine was absorbed significantly more rapidly from one of the formulations than the other two; the bioavailability of this formulation, calculated from intact drug data, normalized for subject differences, was also significantly greater than that of the other two, 68 and 76 per cent respectively. Individual comparisons of area under the curve (AUC) indicated that estimated relative bioavailability depends on the specificity of the assay, the adjustment of the AUC for the area beyond the last measurable plasma concentration and the normalization of the AUC. The data suggest there is a correlation between dissolution rate and peak plasma concentration.