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Orally administered drugs liver

First-pass metabolism is the elimination of an orally administed drug by the liver or sometimes the gut wall, before it reaches the systemic circulation. First-pass metabolism results in a decreased systemic bioavailability. [Pg.507]

First-pass effect (metabolism) The metabolism of a drug when it first passes through the liver. This is one of the major determinants of bioavailability for orally administered drugs. [Pg.242]

The primary indication for standard i.m. administration is when a patient is too disturbed to take oral medication. Because drugs are more rapidly absorbed when given parenterally and their effect occurs about 60 minutes faster than with oral administration (i.e., 30 vs. 90 minutes), violent or otherwise dangerously disturbed patients should initially receive i.m. injections. Further, because orally administered drugs are metabolized in the gut, as well as during their first pass through the liver, less than 50% may reach the systemic circulation for ultimate availability at the intended brain sites. [Pg.64]

Both methods of absorption calculation mentioned are based on the fact that after absorption the drug/metabolites reach the central circulation. In case of oral administered drugs targeting the liver and being eliminated biliary instantly, it is obvious that both methods mentioned fail. In such a special case an absorption estimation might be possible via a biliary excretion study. [Pg.571]

In order to obtain a clinical effect by an orally administered drug, it is, for example, required that the drug is (i) dissolved and released from its formulation, (ii) transported over the mucosal barrier, and (iii) has passed from the lumen to the systemic blood circulation without being metabolized by, for example, the lumen or the liver. The drug dissolution rate and the rate of absorption of the dissolved active substance as well as the relation between these processes are important, in particular the dissolution process since the absorption of undissolved drug particles can be disregarded. [Pg.1194]

The portal blood represents the major pathway for the majority of orally administered drugs as it has higher capacity to transport both water soluble and poorly water soluble compounds. During this process, hydrophilic molecules are carried to the liver via the hepatic portal vein, and then by the hepatic artery gain across to the systemic circulation for subsequent delivery to their sites of action. On the other hand, highly lipophilic drugs (log P > 5) that cross the same epithelial barrier are transported to the intestinal lymphatics, which directly delivers them to the vena cava, thereby bypassing the hepatic first-pass metabolism. ... [Pg.1244]


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See also in sourсe #XX -- [ Pg.428 ]




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