PSY 356 pharmacokinetics 2

PSY 356 pharmacokinetics 2 - PHARMACOKINETICS CONTINUED A....

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PHARMACOKINETICS CONTINUED A. Distribution -once absorbed into the bloodstream, a drug is distributed throughout the body by the circulating blood, passing across various barriers to reach its target or site of action (its receptors) a. Only a very small portion of the totally amount of a drug that is in the body is actually in contact with its receptors i. Most of the administered drug is found in areas of the body that are remote from the drug's site of action ii. This wide distribution often accounts for many of the side effects of a drug 1. Side effects -results that are different from the primary or thereapeutic effect for which a drug is taken b. Action in bloodstream i. Externally absorbed drugs (oral or rectal) 1. Drug passes through the cells lining the GI tract then through the liver 2. Drug enters the central circulaton and is carried to the heart to be distributed throughout the body 3. First-pass metabolism -occassionally when drug-metabolizing enzymes in the cells of either the GI tract or the liver can markedly reduce the amount of drug that reaches the bloodstream ii. Parenterally absorbed drug (all others) 1. Drug bypasses intestinal absorption, rapidly enters veins, and is carried in blood to the right side of the heart a. With minimal amounts passing initially though the liver 2. Drug circulates through the pulmonary vessels, returns to the left side of the heart and finally travels through the aorta tot the brain and body
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PSY 356 pharmacokinetics 2 - PHARMACOKINETICS CONTINUED A....

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