How do i calculate ic50

From the data table, click Analyze, choose nonlinear regression, and choose the panel of equations: Dose-Response -- Special, X is log concentration. Then choose " Absolute IC50, X is log concentration ". You must enter a value for the parameter "Baseline" on the Constrain tab of the analysis parameters dialog.

Note the important distinction between "Baseline" and "Bottom" in this model. While you must constrain the baseline, you may want to consider constraining the "Top" parameter as well. Top and Bottom are plateaus in the units of the Y axis. HillSlope describes the steepness of the family of curves. A HillSlope of 1. A Hill slope greater than 1. Baseline is the measured response of a "standard" drug or control resulting in a maximally inhibited response.

This value must be entered by the user in the constrain tab of the analysis parameters dialog. LogAbsoluteIC50 is the log concentration of antagonist that gives a response half way between Top and Baseline. This is not the same as the response half way between Top and Bottom this is the relative logIC50, and is not reported by this analysis. Prism also reports the AbsoluteIC All rights reserved. Introduction Many dose-response curves follow a familiar sigmoidal shape.

Relative IC50 This is by far the most common definition, and is usually what people mean by "the IC50" of a response. Absolute IC50 The concentration that provokes a response halfway between the blank no antagonist, maximum measured response and some positive control to represent a fully inhibited response is sometimes called the Absolute IC Step by step Create an XY data table. Scroll Prev Top Next More. If you'd like to convert concentration values to log concentration values - or vice versa - you can use Prism's Transform analysis to convert the X values.

Also note that this sample data set includes unknown values. These are Y values without corresponding X values. Prism can interpolate these X values. Click Analyze and then Nonlinear regression. Or click the Nonlinear Regression shortcut button just above the Analyze button. On the Nonlinear regression dialog, open the "Dose-Response -- Inhibition" family of equations, and choose "log inhibitor vs. At the bottom of the dialog, check the option to "Interpolate unknowns from standard curve".

Click OK and view the results. View the graph. More information: More tutorials on curve fitting Learn about the equation used to fit to the data.