IC50 - an estimate of the dose required to produce 50% of the maximal result.Bottom - an estimate of the bottom plateau.The parameters used in the standard three parameter dose-response model are: However, in some situations, it’s necessary to estimate more (or fewer) parameters. The three and four parameter dose-response models are the most common. Start your free trial of Prism today.Ĭhoosing the number of parameters to estimate in the model Prism offers four sets of equations for dose-response curves. Whether or not to normalize your response, Y, values to be between 0 and 100%.Between modeling relative or absolute IC50.If you want to share parameters across multiple experiments.On setting additional parameters (such as the top and bottom) as constant.Between log transforming the concentration values or not.Which parameters to estimate and which to set as fixed.If you are interested in modeling IC50 in GraphPad, in particular, see this guide for choosing your model. There are several initial choices to make when modeling IC50. We choose the convention for the remaining article to discuss the half-maximal response in terms of IC50. Your choice of modeling IC50 or EC50 is simply based on whether you’re modeling an inhibitor (antagonist) or a stimulant (agonist). These include how to fit the endpoint values (effectively the none versus infinite dosing), choosing relative (recommended) versus absolute IC50, and a discussion on normalizing the data (generally unnecessary) so that the response is between 0 and 100. If you haven’t read it already, we recommend this excellent article, which details the ideal IC50 scenario (see photo below) and clarifies several choices that need to be made when fitting IC50. IC50 and EC50 are, respectively, the inhibition and effective concentrations that produce 50% of maximal response from a drug or treatment dose. In this article, we provide a summary, link to additional content, and address some of the frequently asked questions when a model doesn’t fit. We have a lot of great information about IC50 and EC50. In GraphPad, these are found in the curve fitting sections. IC50 and EC50, which are common metrics in pharmacological research, are estimated using dose-response models.
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