The values of drug dose and response are converted to log values to plot in the dose response curve, so that best interpretation can be drawn. Why is it like this?
When we convert the X-axis values (doses) from arithmetic to logarithmic scale, the plotted dose-response curve will be changed from hyperbolic to sigmoid ("S" shape, stretched) and usually, between 25% to 75 % of the Maximum response, the relation between doses and responses will be linear and therefore, better understanding and interpretation can be drawn from this linear area. By this way we can choose optimized dose of substance (i.e. EC50, EC80, etc as appropriate) for mechanistic studies.
I think values are converted to log values for best plotting of dose response curve, so that the if we plot the arithmetic values then these values will go out of the paper and we can not be able to plot all values in small paper for best interpretation of results.
Valus are often converted to log values to reduce the dispersion of data set e.g. If there are set of values between 1 to 100 log values would fall only in the range of 0 to 2. That helps in getting linear response and well data fitting........
When we convert the X-axis values (doses) from arithmetic to logarithmic scale, the plotted dose-response curve will be changed from hyperbolic to sigmoid ("S" shape, stretched) and usually, between 25% to 75 % of the Maximum response, the relation between doses and responses will be linear and therefore, better understanding and interpretation can be drawn from this linear area. By this way we can choose optimized dose of substance (i.e. EC50, EC80, etc as appropriate) for mechanistic studies.
I believe that this practice is due to the fact that response is generally proportional to blood level and that in most cases blood disappearance over time is a first-order process. In this case a semi-log plot of the data will ideally generate a straight line. You can calculate the slope of the line, which allows for additional analysis of the data, such as drug half-life.
Dear Edward Russak
What you say is completely right only for in-vivo studies but not applicable to a dose-response curve of in-vitro studies.
Totally agree with Hosseinsir, that mainly Logarithmic scale for dose is used, as it will convert the plot in to Linear response...
So basically Logarithmic scale is used for linearity of response plot which make ease in finding EC50, useful to compare two responses, etc...
In-vitro reactions may also be described using logarithmic functions, such as ligand-enzyme interactions, which may reflect a dose response in some situations. The Hill equation is related to a logistic function and is in some ways a logarithmic transform of it, i.e. when you plot the Hill function on a log scale it looks identical to a logistic function. This is particularly important if the range of concentrations that results in saturation does not vary over several orders of magnitude. An in-vitro method known as radioimmunoassay utilizes standard curves based upon a logit-log data transformation as well.
In the dose-response research, the response data is always a nonlinear numbers. The behavior of nonlinear numbers needs to be described by nonlinear mathematic and plotted on nonlinear logarithmic scale. I have a good description of nonlinear math for your reading in my writing "The Myth of biological and radiation hormesis" in ResearchGate.
- Badges
- Science topic
- Similar topics
- Chemistry
- Pharmacology