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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.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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