Prodrug 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. Many herbal extracts historically used in medicine contain glycosides (sugar derivatives) of the active agent, which are hydrolyzed in the intestines to release the active and more bioavailable aglycone. For example, salicin is a β-D-glucopyranoside that is cleaved by esterases to release salicylic acid. Aspirin, acetylsalicylic acid, first made by Felix Hoffmann at Bayer in 1897, is a synthetic prodrug of salicylic acid. However, in other cases, such as codeine and morphine,
Tienilic acid the drug and to give covalent binding. The above explanation is a hypothesis. It is still not known (after 15 years) if the reactive intermediate which inactivates the CYP2C9 is the thiophene sulfoxide or the thiophene epoxide. The target on the protein is also not known (could be multiple). However tienilic acid is a good mechanism based inhibitor of CYP2C9 and seems to inactivate it stoichiometrically. Progress in proteomics may one day give the answer. Recent studies indicate that in fact the primary metabolite of tienilic acid (5-OH tienilic acid) cannot be derived from a thiophene-S-oxide intermediate as was previously