Median Effect Concentration

Median Effective Concentration (EC) The concentration of toxicant or intensity of other stimulus which produces some selected response in one half of a test population. 

EC[D]5q Concentration (dose) that has an effect on 50% of a population. Also known as median effect concentration (dose). 

Potency is compared using the median effective concentration (EC50) or median effective dose (ED50), the meanings of which are subtly different. 

Graphic representation of cumulative frequency distribution of selected effects as a function of concentration is also prepared where ratio of median effective concentration is considered for drug selectivity using different endpoints. 

SPY sulfapyridine, SDZ sulfadiazine, SMX sulfamethoxazole, SMZ sulfamethazine, SCP sulfachloropyridazine, STZ sulfathiazole, SCT sulfacetamide, AcSMX N -acetylsulfamethoxazole, AcSDM N -acetylsulfadimethoxine, AcSDZ N -acetylsulfadiazine, EC50 Median effective concentration (mg/L), LC50 Median lethal concentration (mg/L), NOEC No-observed-effect concentration (mg/L) LOEC lowest-observed-effect concentration (mg/L), h hours, min minutes, d days... 

Median effective concentration. Result of the 3 pM 2,3,7,8-TCDD calibration concentration prepared by the participants. 

Algal median effective concentrations (EC50) range from a low of 0.9 mg/L for the blue-green alga Microcystis to 29 mg/L for Selenastrum (71). 

While the median effective concentration (e.g., EC50 or IC502) is often the endpoint of choice (because medians are more consistent and tend to have small confidence intervals), the pT-value like other measurement endpoints based on thresholds favor the determination of lower effective concentration values. The rationale for this approach is based on the premise that it is more meaningful to estimate lower values for determining the hazard/risk posed by toxicant releases to the environment. These values are clearly more helpful in assessing adverse effects, and are indispensable whenever the measured response is less than 50 percent in an undiluted sample. 

Accurate prediction of mixtures of chemicals is one of the future challenges for risk assessment and (Q)SAR modeling. Most compounds are present in the environment at concentrations far below their individual median effective concentration (EC50 or LC50) and possibly below their no-observed-adverse-effect concentrations as well, yet they may contribute to substantial effects through combination with other chemicals. It is theoretically possible to construct a (Q)SAR model to predict mixture effects however, it is generally difficult to validate their predictive power, due to a lack of experimental calibration (Altenburger et al. 2003). Semiempirical... 

ADME-tox absorption, distribution, metabolism, and excretion/toxicologic properties ECS0 median effective concentration IC50 median inhibitory concentration MIC minimum inhibitory concentration MLSMR Molecular Libraries Small Molecule Repository TAACF-NIAID Tuberculosis Antimicrobial Acquisition and Coordinating Facility/ National Institute of Allergy and Infectious Diseases... 

Perform range-finding experiments with the individual mixture components or explore existing knowledge, to determine the toxicity of each component by finding the median effect concentration (EC50) for the endpoint of interest. 

EC/Dx Concentration (dose) that affects designated effect criterion (e.g., a behavioral trait) by x% compared to the control. The EC/D50 is known as the median effective concentration (dose). The EC/D values and their 95% confidence limits are usually derived by statistical analysis of effects in several test concentrations, after a fixed period of exposure. The duration of exposure must be specified (e.g., 96-hour EC50). See also LC/Dx. 

EC50 Median effective concentration, the concentration causing 50% reduction of a certain response parameter (e.g., reproduction, growth). 

Vedaprofen is a propionic acid derivative that, like carprofen and ketoprofen, exists as two enantiomers with different pharmacokinetic profiles in the horse. For example, the plasma disposition of S(-t-)-vedaprofen is characterized by a very rapid decline with a plasma half-life of less than 1 h while R(-)-vedaprofen has a more prolonged elimination phase with a plasma half-life of over 2h (Lees et al 1999). Both enantiomers also accumulate in and exhibit a delayed elimination from inflammatory exudates. In horses, vedaprofen appears to be slightly selective for the COXl enzyme. For example, the median effective concentration for inhibition of serum TXB2 production, which is assumed to be a reflection of COXl activity, was much lower than that for inhibition of inflammatory infiltrate PGE2 production, which is assumed to be a reflection of COX2 activity. Although the results of these studies are promising, there are no published data on the clinical effectiveness and safety of vedaprofen in horses. 

Median effective concentrations for inhibition of the proliferation of five glioma cell lines by a variety of camptothecin derivatives... 

Results of all bioassays are reported as TOEC values, so a value can be entered into the PEEP index even if no inhibitory concentration (IC) or median effective concentration (EC50) was determined. The TOECs are converted to toxic units. The PEEP is calculated as the sum of the toxic units, including both before and after biodegradation, according to the following formula ... 

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