{"id":49,"date":"2019-04-23T13:58:06","date_gmt":"2019-04-23T13:58:06","guid":{"rendered":"https:\/\/sepia2.unil.ch\/pharmacology\/?page_id=49"},"modified":"2019-04-25T07:23:46","modified_gmt":"2019-04-25T07:23:46","slug":"absorption","status":"publish","type":"page","link":"https:\/\/sepia2.unil.ch\/pharmacology\/mechanisms\/absorption\/","title":{"rendered":"Absorption"},"content":{"rendered":"\n

“Irreversible transfer processes, which transfer a drug from its site of administration to the systemic circulation’<\/p>(Definition)<\/cite><\/blockquote>\n\n\n\n

Description<\/h3>\n\n\n\n
\n
\n

By definition, a drug administered intravenously<\/a> undergoes immediate and complete absorption. By contrast, drugs administered extravascularly<\/a> need to be carried through various barriers in order to be able to reach the blood circulation and then their site of action.\n<\/p>\n\n\n\n

The movement of drug through membranes is an \nessential step in absorption and is influenced by the physicochemical \nproperties of the drug molecule, the nature of the membrane, the \nperfusion of the absorption site and the local pH.\n<\/p>\n<\/div>\n\n\n\n

\n

In the gastrointestinal tract the drug can be \ndegraded by gastric acidity, intestinal membrane enzymes, complexion \nwith food constituents or bacterial enzymes. After absorption through \nthe intestinal epithelium, drugs can be secreted back into the \nintestinal lumen through active transporters such as the P-glycoprotein \n(PGp). Some drugs are further metabolized as a consequence of hepatic first-pass effect<\/a>,\n which also limits their absorption (even when intestinal uptake is \nefficient). The sublingual route and to some extent the rectal route can\n be used to by pass this first-pass effect. This influences the bioavailability<\/a> of the drug.\n<\/p>\n\n\n\n

Drugs administered intramuscularly or subcutaneously\n are completely absorbed unless destruction occurs at the site of \nadministration or during lymphatic first-pass (e.g. for macromolecules \nsuch as vaccines). Absorption from these sites is highly dependant on \nthe blood flow at the site of injection. <\/p>\n\n\n\n

Clinical implications<\/h3>\n\n\n\n

Delays or loss of drug during absorption can introduce a large variability<\/a> in drug response. Disease<\/a> conditions and co-medications<\/a> may profoundly affect the absorption of certain drugs.

The\n route of administration of a drug must be chosen in function of the \nabsorption profile expected, it’s convenience and cost. While the most \nconvenient is the oral route, for some drugs, it allows little \nabsorption. Oral absorption can however be enhanced by galenic formulation<\/a> for certain drugs.<\/p>\n\n\n\n

Related terms<\/h3>\n\n\n\n

Absorption rate constant<\/a> (ka)\n<\/p>\n\n\n\n

Prodrug : In order to circumvent incomplete \nabsorption, a more absorbable derivative of the drug can be \nadministered. This derivate compound will be converted to the active \nmolecule within the body.\n<\/p>\n\n\n\n

Galenics<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

“Irreversible transfer processes, which transfer a drug from its site of administration to the systemic circulation’ (Definition) Description By definition, a drug administered intravenously undergoes immediate and complete absorption. By contrast, drugs administered extravascularly need to be carried through various barriers in order to be able to reach the blood circulation and then their site … <\/p>\n

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