Examples include: As a sulfonamide antibiotic, sulfanilamide functions by competitively inhibiting (that is, by acting as a substrate analogue of) enzymatic reactions involving para-aminobenzoic acid (PABA).

[5][10] PABA is needed in enzymatic reactions that produce folic acid, which acts as a coenzyme in the synthesis of purines and pyrimidines.

[11] However, this effect can be reversed by adding the end products of one-carbon transfer reactions, such as thymidine, purines, methionine, and serine.

[5][12][11] Sulfanilamide was first prepared in 1908 by the Austrian chemist Paul Josef Jakob Gelmo (1879–1961)[13][14] as part of his dissertation for a doctoral degree from the Technische Hochschule of Vienna.

[16] Gerhard Domagk, who directed the testing of the prodrug Prontosil in 1935,[17] and Jacques Tréfouël and Thérèse Tréfouël, who along with Federico Nitti and Daniel Bovet in the laboratory of Ernest Fourneau at the Pasteur Institute, determined sulfanilamide as the active form,[18] are generally credited with the discovery of sulfanilamide as a chemotherapeutic agent.

[5] Since sulfanilamide is used almost exclusively in topical vaginal preparations these days, adverse effects are typically limited to hypersensitivity or local skin reactions.