A method for presenting and comparing dose-response curves.

When dose-response curves are replicated, averaging the responses to each dose of drug reduces the slope of the mean curve. The shape of the curve can be preserved, however, by first normalizing each dose-response curve and then interpolating log concentrations that induce predetermined responses. These log concentrations are averaged, and then the responses are scaled to the mean maximal response. Mean dose-response curves obtained using this method were compared with mean curves obtained by the conventional method. It was found that this method did not distort the slope of the curve, and smaller differences were detected as significant. Neither method was found to be satisfactory for obtaining a truly representative mean curve for biphasic dose-response curves. The nature of the distribution of EC50 and maximal response was investigated, and it was confirmed that EC50 are log-normally distributed, whereas maximal responses are normally distributed.