Types of drug synergism classified by the concentration-action curve

Abstract

Using excised intestine and seminal vesicle of rabbits and abdominal rectus muscle of frogs, the modification of the C-A curves. of the active drugs : acetylcholine, pilocarpine, adrenaline and BaCl₂, by the presence of their respective synergists was compared. Results : 1) The formula Kxⁿ=y/y_max-y (x : drug conc., y : intensity of action measured by tonus rise, y_max : maximum action, K, n : constants) suited best with the C-A curves of the active drugs in the absence and presence of the synergists among other formulae. The synergists modified the values of K and/or y_max in various ways, but not the value of n. 2) Based on the pattern of modification of the values of K and/or y_max, 5 different types of synergism have been classified and exemplified, and further, an assumption has been made of the existence of two factors, “susceptibility” and “reactivity” for the drug “sensìtivity” of the tissue.