A prodrug is a medication that is initially administered to the body in an inactive (or less than fully active) forms, and then becomes converted to its active form through the normal metabolic processes of the body.
A prodrug serves as a type of precursor to the intended drug. Prodrugs can be used to improve how the intended drug is absorbed, distributed, metabolized and excreted (ADME). Prodrugs are often designed to improve oral bioavailability in cases where the intended drug is poorly absorbed through the gastrointestinal tract.
Prodrugs can be classified into two major types, based on how the body converts the prodrug into the final active drug form:
- Type I prodrugs are bioactivated inside the cells (intracellularly). Example: anti-viral nucleoside.
- Type II prodrugs are bioactivated outside cells (extracellularly), especially in digestive fluids or in the body’s circulation system particularly in the blood. Examples: salicin.
Prodrug approaches for improved oral bioavailability like increased aqueous solubility, increased lipophilicity, and Transporter-mediated drug delivery.
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