log10EC50

Log10EC50 is the base-10 logarithm of the EC50 value, where EC50 is the concentration of a drug or ligand that produces 50% of its maximum observable effect in a given biological system. The EC50 is typically derived from a dose–response curve and is often modeled with the Hill equation: Response = Emax × [C]^n / (EC50^n + [C]^n). In this framework, EC50 is the concentration at which the response reaches half of Emax, regardless of the Hill coefficient n.

Taking the logarithm of EC50 is common because effective concentrations often span several orders of magnitude. log10EC50 can be used to compare potencies and to stabilize variance in statistical analyses. It is related to the pEC50 statistic by pEC50 = -log10(EC50), provided EC50 is expressed in molar units; thus a lower EC50 corresponds to higher potency, and a higher pEC50 indicates higher potency.

Applications include pharmacology, toxicology, and biochemistry, where log10EC50 (or pEC50) values are reported to compare compounds and to calibrate dose–response relationships. When reporting log10EC50, the units of EC50 influence the value, so EC50 should be expressed in consistent units (typically molarity) to permit valid cross-study comparisons.

Caveats include that EC50 is assay- and condition-dependent and does not reflect differences in efficacy or maximal effect between compounds. Estimates rely on nonlinear regression of experimental data, and reported log10EC50 should be interpreted within the context of the experimental setup.