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The ED50 is commonly used as a measure of the reasonable expectancy of a drug effect, but does not necessarily represent the dose that a clinician might use. This depends on the need for the effect, and also the toxicity. The toxicity and even the lethality of a drug can be quantified by the TD 50 and LD 50 respectively. Ideally, the effective ...
Even less safe are drugs such as digoxin, a cardiac glycoside; its therapeutic index is approximately 2:1. [12] Other examples of drugs with a narrow therapeutic range, which may require drug monitoring both to achieve therapeutic levels and to minimize toxicity, include dimercaprol, theophylline, warfarin and lithium carbonate.
For clarification, a graded dose response curve shows the graded effect of the drug (y axis) over the dose of the drug (x axis) in one or an average of subjects. 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).
This reflects how dose–response relationships can be used in individuals. In populations, dose–response relationships can describe the way groups of people or organisms are affected at different levels of exposure. Dose response relationships modelled by dose response curves are used extensively in pharmacology and drug development.
Intrinsic activity (IA) and efficacy (E max) refer to the relative ability of a drug-receptor complex to produce a maximum functional response. This must be distinguished from the affinity, which is a measure of the ability of the drug to bind to its molecular target, and the EC 50, which is a measure of the potency of the drug and which is proportional to both efficacy and affinity.
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 ]
For the drugs administered by oral and dermal route, the units of threshold dose are mg/kg body-weight/day (dose of the drug in mg per body weight in kg per day) or ppm (parts per million), while the threshold dose of drugs by inhalation delivery has the unit of mg/L 6h/day (amount of drug in mg in 1L of air, for 6 hours per day). [8]
In practice, the drug concentration is measured at certain discrete points in time and the trapezoidal rule is used to estimate AUC. In pharmacology, the area under the plot of plasma concentration of a drug versus time after dosage (called “area under the curve” or AUC) gives insight into the extent of exposure to a drug and its clearance ...