Lack of bioequivalence between disulfiram formulations. Exemplified by a tablet/effervescent tablet study

A comparison of the bioavailability of disulfiram (DSF) after administration of non-effervescent Antabuse tablets (CP Pharmaceuticals, UK) and Antabuse effervescent tablets Antabuse (A/S Dumex, DK) has been made in two cross-over studies. The first study included 6 volunteers who were given 400 mg DSF after an overnight fast. The bioavailability of DSF after administration of non-effervescent was found to be only 27% of that achieved with effervescent tablets. The second study included 24 volunteers who were given 800 mg DSF after a light standardized meal. The relative bioavailability of DSF after administration of non-effervescent compared with effervescent tablets was found to be only 34%. In addition to the difference in bioavailability of DSF after administration of the two preparations, a considerable difference was seen between the two studies. A light meal seems both to increase the bioavailability of DSF and to reduce the interindividual variation. A two to threefold increase in the bioavailability of DSF was found. Thus, the bioavailability of DSF appears to depend on both the formulation (preparation) and the mode of administration. A lack of bioequivalence between the two investigated DSF preparations was found.