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Dose–response relationships can be described by dose–response curves. This is explained further in the following sections. This is explained further in the following sections. A stimulus response function or stimulus response curve is defined more broadly as the response from any type of stimulus, not limited to chemicals.
A quantal dose response curve shows the percentage of subjects where a response is noted in an all-or-none manner (y axis) over the dose of the drug (x axis). For competition binding assays and functional antagonist assays IC 50 is the most common summary measure of the dose-response curve
The IC 50 of a drug can be determined by constructing a dose-response curve and examining the effect of different concentrations of antagonist on reversing agonist activity. IC 50 values can be calculated for a given antagonist by determining the concentration needed to inhibit half of the maximum biological response of the agonist. [4]
Stochastic health effects are those that occur by chance, and whose probability is proportional to the dose, but whose severity is independent of the dose. [3] The LNT model assumes there is no lower threshold at which stochastic effects start, and assumes a linear relationship between dose and the stochastic health risk.
The threshold dose-response model is widely viewed as the most dominant model in toxicology. [6] An alternative type of model in toxicology is the linear no-threshold model (LNT), while hormesis correspond to the existence of opposite effects at low vs. high dose, which usually gives a U- or inverted U-shaped dose response curve.
Each curve corresponds to a different Hill coefficient, labeled to the curve's right. The vertical axis displays the proportion of the total number of receptors that have been bound by a ligand. The horizontal axis is the concentration of the ligand. As the Hill coefficient is increased, the saturation curve becomes steeper.
Simple illustration of the effects of excess antigen and dosage response curve. Examples include high levels of syphilis antibodies in HIV patients or high levels of cryptococcal antigen leading to false negative tests in undiluted samples. [7] [8] This phenomenon is also seen in serological tests for Brucellosis.
Dose response curves of a full agonist, partial agonist, neutral antagonist, and inverse agonist. In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist.