What is a prodrug?
A prodrug is a chemical compound, which gets metabolized into a pharmacologically active form (drug) inside the body after its administration. Most of the prodrugs are derived from the active drug by adding a chemical promoiety, which undergoes one or two-step chemical/enzymatic transformation to convert to the parent active drug.
Why a prodrug?
The prodrug approach offers opportunities to overcome pharmacokinetic barriers such as:
- Poor aqueous solubility
- Poor oral/dermal/opthalmic absorption
- Inability to cross blood-brain barrier
- Toxicity
- Fast pre-systemic metabolism
- Chemical instability
In some cases, a prodrug may consist of two pharmacologically active drugs that are coupled together in a single molecule (co-drug) so that each drug acts as a promoiety for the other. A bioprecursor prodrug is a prodrug that does not contain a carrier or promoiety, but results from a molecular modification of the active agent itself.
This modification (for example, oxidation or reduction) generates a new compound that can be trans- formed metabolically or chemically, with the resulting compound being the active agent (it can also be referred to as an active metabolite).