Quantal Responses to Mixtures of Drugs

Abstract

THE joint action of two drugs can be termed ‘non-interactive’ if, when applied together, neither modifies the physiological action of the other that leads to the response under consideration¹. We have previously formulated the relation between dose and quantal response for the extreme forms of this type of joint action, namely, simple similar action¹, in which the drugs act on the same physiological system, and independent action^1,2, in which they act on different systems. The relation for independent action allowed different degrees of correlation of the tolerances for the respective drugs ; but the relation for simple similar action allowed only their complete positive correlation. We have now extended this work, first to cover types of non-interactive joint action intermediate between the extreme forms, and secondly, to permit any degree of correlation of tolerances for every form of non-interactive joint action. Since interactive joint action can be formulated as a generalization of non-interactive¹, the whole theory of quantal responses to mixtures of drugs is thereby unified.