concentration of phenylephrine at which the force of blood vessel contraction is half the maximum value (EC50) logarithm of the concentration of phenylephrine at which the force of blood vessel contraction is half the maximum value (Log EC50) 2012-03-14T04:17:54Z A calculated value for logarithm of the concentration of phenylephrine (PE), the phenylethanolamine with IUPAC name (R)-3-[-1-hydroxy-2-(methylamino)ethyl]phenol and formula C9H13NO2 that acts as a selective alpha1-adrenergic receptor agonist, decongestant and vasoconstrictor, at which the energy produced by the active reduction in the diameter of a blood vessel in response to the application of PE is halfway between the baseline value and the highest achievable value of such PE-induced contractile energy. The logarithm of the concentration is the exponent indicating the power to which 10 must be raised to obtain that concentration value. CHEBI:8093 CMO:0000722 JSmith VT:0000198 clinical_measurement_ontology phenylephrine Log half maximal effective concentration (Log EC50) logarithm of the concentration of vasoconstrictor at which the force of blood vessel contraction is half the maximum value (Log EC50)