Definition of Efficacy

efficacy drug

The ability of a drug to produce a predictable effect in the body. Many factors influence a drug’s efficacy, from foods and other drugs to health conditions and a person’s metabolic characteristics.

An individual’s age, weight, gender, and level of activity also may affect the rate at which a drug enters, and how long it stays in, the blood circulation. It is a key factor in determining a drug’s potential effectiveness to treat a particular condition in a specific individual.

Some drugs have greater efficacy in younger people, for example. Other factors that are also relevant include bioavailability and bioequivalence.

See also CYTOCHROME P450 (CYP450) ENZYMES; THERAPEUTIC WINDOW.

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