[A modified procedure for estimating pA2--equi-concentration effect method].

This new procedure was proposed under the necessity of a fixed concentration of an agonist in the absence/presence of an antagonist. As the odds ratio (OR) of the effects in the absence/presence of the antagonist under a fixed concentration is equal to the equi-effective dose ratio (DR) under a fixed effect, it is possible to substitute OR for DR in A - S equation. Since the experiment is less expensive and more convenient than that of Arunlakshana and Schild, and the procedure for obtaining OR is much more time-saving and economic than that for obtaining DR, it is worthy for analyzing a competitive antagonist.