Absorption of quinidine and dihydroquinidine in humans.

Quinidine and dihydroquinidine were administered as the sulphates in an oral solution to seven healthy volunteers. In all subjects, dihydroquinidine was absorbed to a lesser extent than quinidine. On the basis of comparative AUC pu to 6 h after administration, dihydroquinidine was 73% as available as quinidine. Rates of elimination of the compounds were similar. No correlation could be found between saliva and plasma levels for either compound. Limits for content of dihydroquinidine in commercial quinidine preparations seem essential to ensure adequate bioavailability.