CombiTool--a new computer program for analyzing combination experiments with biologically active agents.

CombiTool is a new computer program for the analysis of combination effects of biologically active agents. It performs model calculations and an analysis of experimental combination effects for two or three agents according to both the Bliss independence and the Loewe additivity criteria. Zero interaction response surfaces are calculated from single-agent dose-response relations and compared to experimental combination data. The calculation of response surfaces for Loewe additivity is based on a new approach which combines the implicit definition equation in terms of doses alone with single-agent dose-response relations. The simultaneous analysis of experimental data according to both Loewe additivity and Bliss independence within one program can hopefully contribute to a better understanding of the meaning and limits of the two criteria. CombiTool has a built-in graphics facility which allows the direct visualization of the response surfaces or the corresponding contour plots and the experimental data.