Dose response is the change in effect on an organism caused by differing levels of exposure to a substance. This may apply to individuals (eg: a small amount has no observable effect, a large amount is fatal), or to populations (eg: how many people are affected at different levels of exposure).
Studying dose response, and developing dose response models, is central to determining "safe" and "hazardous" levels and dosages for drugs, potential pollutants, and other substances that humans are exposed to. These conclusions are often the basis for public policy.
Studying doseresponse, and developing doseresponse models, is central to determining "safe" and "hazardous" levels and dosages for drugs, potential pollutants, and other substances that humans are exposed to.
The measured dose (usually in milligrams, micrograms, or grams per kilogram of body-weight) is generally plotted on the X axis and the response is plotted on the Y axis.
Commonly, it is the logarithm of the dose that is plotted on the X axis, and in such cases the curve is typically sigmoidal, with the steepest portion in the middle.
In this case, a dose that is 50-75% effective does not cause toxicity whereas a 90% effective dose may result in a small amount of toxicity.
It is the ratio of the dose producing toxicity to the dose needed to produce the desired therapeutic response.
The use of the ED50 and LD50 doses to derive the TI may be misleading as to safety, depending on the slope of the dose-response curves for therapeutic and lethal effects.
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