Absolute quinidine bioavailability

Abstract

The absolute bioamilability of quinidine was studied in II hospitalized patients. A 400-mg dose of quinidine gluconate was administered to each patient In intravenous infusion and as an oral solution. Drug treatments were separated by a 72-hr period. In 8 patients. peak plasma quinidine concentrations were reached in 65 min after the oral dose; in the remaining 3 subjects. peak concentrations were reached later. From the ratio of the roral area under the plasma concenfration-time curves (AUC^oralAUC^ir). the absolute bioamilability of quinidine rangedfrom 44% to 89%, (mean. 72). In 8 patients. the ratio of the total amount of quinidine excreted in the urine in 48 hr (Au^oral/Au^ir) indicated that the extent of quinidine biovailability varied from 47% to 96% (mean. 73). The predicted biovailability of quinidine due to first-pass effects was 76 = 11%. It is concluded that absorption atter the oral solution was rapid and that the reduction of quinidine bioavailability was due to first-pass hepatic drug revoral.