parameter type ec50 EC50 PSI-MI MI:0642 Molar concentration of an agonist which produces 50% of the maximum possible response for that agonist. Note this measure depends on the specific agonist used and upon experimental conditions, notably temperature, pH and solution composition (e.g., salts, chelating agents and others). Thus the ec50 is a relative measure and its values can be compared only when sharing the same experimental setting. Unit Molar.