Sublingual nitroglycerin. II. In vitro and in vivo availability of Nitrostat and Nitrobaat tablets

The in vitro and in vivo availability of nitroglycerin from three compressed and one stabilized molded tablet have been studied. Compressed nitroglycerin tablets have to disintegrate before the drug is released. The disintegration and release of nitroglycerin from these tablets appeared to be strongly dependent upon conditions in the in vitro dissolution tests, such as the degree of agitation, and in vivo factors, such as tongue pressure and/or movement. The stabilized molded nitroglycerin tablet did not disintegrate but dissolved completely. Because the dissolution of the molded tablet was fast, the release rate of nitroglycerin was far less influenced by the in vitro and in vivo factors described above. The potency and in vitro and in vivo availability of fresh tablets and tablets which had been stored in tightly closed glass containers for over one year did not differ significantly. It is conjectured that the supposed potency loss of properly stored compressed nitroglycerin tablets is rather a release problem than a stability problem.