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In pharmacology, potency or biological potency [1] is a measure of a drug's biological activity expressed in terms of the dose required to produce a pharmacological effect of given intensity. [2]
Acute use (1–3 days) yields a potency about 1.5× stronger than that of morphine and chronic use (7 days+) yields a potency about 2.5 to 5× that of morphine. Similarly, the effect of tramadol increases after consecutive dosing due to the accumulation of its active metabolite and an increase of the oral bioavailability in chronic use.
It is commonly used as a measure of a drug's potency, although the use of EC 50 is preferred over that of 'potency', which has been criticised for its vagueness. [3] EC 50 is a measure of concentration, expressed in molar units (M), where 1 M is equivalent to 1 mol / L .
The parameters of the dose response curve reflect measures of potency (such as EC50, IC50, ED50, etc.) and measures of efficacy (such as tissue, cell or population response). A commonly used dose–response curve is the EC 50 curve, the half maximal effective concentration, where the EC 50 point is defined as the inflection point of the curve.
Intrinsic activity (IA) and efficacy 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.
A drug's potency can be affected (the response curve shifted to the right) by the presence of an antagonistic interaction. Pharmacodynamic interactions can occur on protein receptors . [ 5 ] Two drugs can be considered to be homodynamic , if they act on the same receptor.
Explore the concept of PK/PD models, which integrate pharmacokinetics and pharmacodynamics to optimize drug dosing and efficacy.
Half maximal inhibitory concentration (IC 50) is a measure of the potency of a substance in inhibiting a specific biological or biochemical function. IC 50 is a quantitative measure that indicates how much of a particular inhibitory substance (e.g. drug) is needed to inhibit, in vitro , a given biological process or biological component by 50% ...