Synergism and Drug-receptor.

a Drugs A and B have similar activity. a -l When the effective doses of A and B in combination are located in the area of m+n 1, m> 1, n> 1, they are called par tial antagonism. a -4 When they are located out of the square area, that is, m)1, or n> 1, they are antagonistic. b Drug B does not have the same pharmacological action as drug B. b-1 In the area m 1, they are antagonistic. In the study of the drug-receptor interaction, the analysis of the mode of drug antagonism had been the objects of the principal interests, and the drug-synergism had only been remarked in passing (1). Veldstra (2) mentioned the relation between drug receptor and synergism in his extensive review on "Synergism and Potentiation". A fine definition of synergism and antagonism was proposed by Gaddum as follows. Figure 1 is some modification of that shown in his textbook. In the abscissa a multiple "m" of the effective concetration of the drug A and in the ordinate a multiple "n" of that of the drug B is shown. The synergistic effect is divided into the following