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FIGURE 1-1 The interrelationship of the absorption, distribution, binding, metabolism, and excretion of a drug and its concentration at its sites of action. Possible distribution and binding of metabolites in relation to their potential actions at receptors are not depicted.

requires dissolution of the tablet or capsule, thus liberating the drug to be absorbed into the local circulation from which it will distribute to its sites of action. Bioavailability indicates the fractional extent to which a dose of drug reaches its site of action, taking into account, for example, the effects of hepatic metabolism and biliary excretion that may occur before a drug taken orally enters the systemic circulation. If hepatic elimination of the drug is large, bioavailability will be reduced substantially (the first-pass effect). This decrease in availability is a function of the anatomical site from which absorption takes place; other anatomical, physiological, and pathological factors can influence bioavailability (see below), and the choice of the route of drug administration must be based on an understanding of these conditions.

10 Ways To Fight Off Cancer

10 Ways To Fight Off Cancer

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