[Bioavailability of delayed-action and non-delayed-action preparations of isosorbide-5-nitrate]

In a randomized crossover study on twelve healthy test subjects, the plasma concentration of isosorbide-5-nitrate (IS-5-N) after oral administration of 40 mg IS-5-N daily from two standard preparations (two tablets Ismo 20 or Corangin 20) and two sustained release preparations with 40 mg or 60 mg IS-5-N (one tablet Corangin 40 or Corangin 60) once a day was determined. The concentrations were measured in the first and in the third dose interval (24 hours). The respective pharmacokinetic parameters (AUC, Cmax and tmax) of the first and the third day only differed slightly. The two standard formulations proved to be bioequivalent. With the two sustained release preparations, maximum plasma concentrations attained after five to six hours were measured which were lower by roughly the factor 2. The sustained release preparations showed a low loss of bioavailability of 13-19% as compared to the nonretarded standard formulations.