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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

Drug absorption

Absorption is the process by which a drug proceeds from the site of administration to

the site of measurement (usually blood, plasma or serum).

Membranes and the mechanism of drug transport

Drugs administered by extravascular routes may be intended for local effect or to

be absorbed from the site of administration into the systemic circulation.

For systemic drug absorption, the drug may cross cellular membranes and access to

the bloodstream, where the distribution process will take it to the ‘‘site of action.

Membrane that separates the lumen of the stomach and the intestine from the

systemic circulation and site of drug absorption is a complex structure.

• It is made up of lipids, proteins, lipoproteins and polysaccharide material

• It is semipermeable in nature or selectively permeable (i.e. allowing rapid

passage of some chemicals while restricting others).

• For example: amino acids, sugars and fatty acids will cross the membrane, while

virtually no transfer of plasma proteins and certain toxins will occur.

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