A simple and accurate mathematical method for calculation of the EC50

A simple, accurate, and speedy noncomputational technique for the calculati on of the EC50 or any other concentration-related parameter of concentratio n-effect curves is presented. It avoids the necessity for graph constructio n or computational curve-fitting programs and allows accurate calculation o f the EC50, where the value falls between two known concentrations The tech nique has been applied to a concentration-response curve constructed to hep atic arterial (HA) vasoconstrictor responses to HA injections of noradrenal ine in an isolated dual-perfused rat liver preparation. EC50 values calcula ted by the new technique were compared to those calculated by conventional, established, noncomputational techniques. The new technique is faster, mor e accurate, and simpler to perform than other established noncomputational techniques used for the calculation of the EC50 and can be widely applied t o many other pharmacological investigations. (C) 1999 Elsevier Science Inc. All rights reserved.