Extra notes: Biopharmaceutical

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Buccal, respiratory, rectal, intramuscular or subcutaneous routes of drug administration, transport the drug from the absorbing tissue into circulating blood supply.

Intravenous route is the most direct route and absorption is 100%.

Drug substances will remain foreign substances to the body and will undergo distribution, metabolism and excretion.

Drugs and their metabolites may be excreted via the urine, faeces, saliva, skin or lungs.

Drug absorption form the GIT is an involved process as drugs need to pass through the biological membrane:

Lipophillic membrane

Surface of lumen is charged

Small molecules like lithium and urea may pass through aqueous pores

K1 and K2 are partition coefficients