[Comparative studies on the study of drug-excipient interactions with vapor pressure osmometry and equilibrium...

The authors discuss how far the vapour osmometry enables to make statements on the interaction between drugs and macromolecular agents as well as on their dependence upon various test parameters. The results are compared to those of the equilibrium dialysis. Sulfathiazole sodium and the polyvinylpyrrolidones PVP K 25 and PVP K 90 are used the sample substances. Concerning the interaction dependence upon the concentrations of drugs or agents, resp., both the methods revealed findings of comparable trends. An increased agent concentration or a reduced drug concentration results in an increased sulfathiazole-PVP interaction. An exothermic binding process can be derived from tonometric and dialysis results. Vapour osmometric measurements not only restricting to the interactions drugs-agents, but also recording all the interactions caused by variations of the particle number, the findings obtained by means of buffered solution do not permit a comparability of both the methods. Although the equilibrium dialysis takes precedence in the exact registration of drug-agent interactions, the vapour osmometry has an advantage in the registration of drug interactions with membrane-permeating agents.