ABSTRACT
In the introductory part a new classification of joint drug actions is submitted, according which three fundamental types are distincted, named respectively interference, cooperation and true interaction. In its turn, interaction is subdivided in three classes (uni-effectual, bis-ineffectual, bis-effectual) in the last of which is placed the most relevant of the interactions, that is synergism, subclassified, at its turn, as additive, super and infra-additive. The second part is devoted to the classification of the bacteriological techniques hitherto proposed in order to evaluate in vitro and in vivo the antibacterial interaction of chemoantibiotics. The third part is devoted to the classification and critical analysis of biometrical techniques hitherto applied to above quoted bacteriological techniques in order to obtain a quantitative evaluation of interaction. Criticism versus isobolic model is pointed out. In the final part a new procedure, named isoeffectual, is proposed. According to such a procedure a close grid of single and joint concentrations of a couple of chemoantibiotics, broad enough in order to cover the whole of the effects to be explored, is tested in vitro adopting the one-center agar diffusion test or a liquid medium. The experimental data so obtained are related in a planar diagram to the log of the sum obtained by adding to the concentrations of the first the concentrations of the second agent, converted into equi-effectual concentrations of the first. By this way a series of curvilinear regressions is obtained, which may be all explained by a mathematical formula according which the data may be submitted to statistical analysis and elaborated in order to draw the parameters able to define quantitatively the interaction. The model so applied is discussed as a general model for joint drug action.
