Product Code Database
A prodrug is a pharmacologically inactive medication or compound that, after intake, is Drug metabolism (i.e., converted within the body) into a pharmacologically active drug. (2025). 9780080919225, Academic Press. ISBN 9780080919225 Instead of administering a drug directly, a corresponding prodrug can be used to improve how the drug is absorbed, distributed, metabolized, and excreted (ADME).
Prodrugs are often designed to improve bioavailability when a drug itself is poorly absorbed from the gastrointestinal tract. A prodrug may be used to improve how selectively the drug interacts with cells or processes that are not its intended target. This reduces adverse or unintended effects of a drug, especially important in treatments like chemotherapy, which can have severe unintended and undesirable side effects.
The first synthetic antimicrobial drug, arsphenamine, discovered in 1909 by Sahachiro Hata in the laboratory of Paul Ehrlich, is not toxic to bacteria until it has been converted to an active form by the body. Likewise, prontosil, the first sulfa drug (discovered by Gerhard Domagk in 1932), must be cleaved in the body to release the active molecule, sulfanilamide. Since that time, many other examples have been identified.
Terfenadine, the first non-sedating antihistamine, had to be withdrawn from the market because of the small risk of a serious side effect. However, terfenadine was discovered to be the prodrug of the active molecule, fexofenadine, which does not carry the same risks as the parent compound. Therefore, fexofenadine could be placed on the market as a safe replacement for the original drug.
Loratadine, another non-sedating antihistamine, is the prodrug of desloratadine, which is largely responsible for the antihistaminergic effects of the parent compound. However, in this case the parent compound does not have the side effects associated with terfenadine, and so both loratadine and its active metabolite, desloratadine, are currently marketed.UK Medicines Information Pharmacists Group. New Medicines on the Market: Desloratadine. June 2001.
Both major types can be further categorized into subtypes, based on factors such as (Type I) whether the intracellular bioactivation location is also the site of therapeutic action, or (Type 2) whether or not bioactivation occurs in the gastrointestinal fluids or in the circulation system.
| +Classification of prodrugs |
| Aciclovir, fluorouracil, cyclophosphamide, diethylstilbestrol diphosphate, L-DOPA, mercaptopurine, mitomycin, zidovudine, Hypoxia-activated prodrugs |
| Carbamazepine, captopril, carisoprodol, heroin, molsidomine, leflunomide, paliperidone, phenacetin, primidone, psilocybin, sulindac, fursultiamine |
| Loperamide oxide, oxyphenisatin, sulfasalazine |
| Acetylsalicylate, bacampicillin, bambuterol, chloramphenicol succinate, dipivefrin, fosphenytoin, lisdexamfetamine, pralidoxime |
| ADEPTs, , |
Importantly, prodrugs can belong to multiple subtypes (i.e., Mixed-Type). A Mixed-Type prodrug is one that is bioactivated at multiple sites, either in parallel or sequential steps. For example, a prodrug, which is bioactivated concurrently in both target cells and metabolic tissues, could be designated as a "Type IA/IB" prodrug (e.g., HMG Co-A reductase inhibitors and some chemotherapy agents; note the symbol " / " applied here). When a prodrug is bioactivated sequentially, for example initially in GI fluids then systemically within the target cells, it is designated as a "Type IIA-IA" prodrug (e.g., tenofovir disoproxil; note the symbol " - " applied here). Many antibody- virus- and gene-directed enzyme prodrug therapies (ADEPTs, VDEPT, GDEPT) and proposed nanoparticle- or nanocarrier-linked drugs can understandably be Sequential Mixed-Type prodrugs. To differentiate these two Subtypes, the symbol dash " - " is used to designate and to indicate sequential steps of bioactivation, and is meant to distinguish from the symbol slash " / " used for the Parallel Mixed-Type prodrugs.; Table 1; Table 1
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