Sulfacytine is a short-acting sulfonamide, which was used for the treatment uncomplicated urinary tract infections, but was discontinued. This drug is a is a competitive inhibitor of the dihydropteroate synthetase, that inhibits bacterial synthesis of dihydrofolic acid by preventing the condensation of the peridine with para-aminobenzoic acid (PABA), a substrate of the enzyme dihydropteroate synthetase.

Sulfametoxydiazine (INN) or sulfamethoxydiazine (USAN: sulfameter) is a long-acting sulfonamide antibacterial, shows bacteriostatic effects against Gram positive and Gram negative bacteria in vivo. It is used as a leprostatic agent and in the treatment of urinary tract infections. Orally active. Sulfonamides block the synthesis of dihydrofolic acid by inhibiting the enzyme dihydropteroate synthase. Sulfonamides are competitive inhibitors of bacterial para-aminobenzoic acid (PABA), which is required for bacterial synthesis of folic acid. Sulfameter is a dihydrofolate reductase (DHFR) inhibitor. Mode of resistance is via the alteration of dihydropteroate synthase or alternative pathway for folic acid synthesis.

Sulfaphenazole is an oral antibiotic, which was used for the treatment of bacterial infections under the name Sulfabid. The drug was found to block folate synthesis in bacterias by inhibiting the enzyme dihydropteroate synthase. Sulfaphenazole is also known to inhibit CYP2C9 with high potency and specificity. Sulfabid is no longer marketed in the USA.

Sulfachlorpyridazine is a broad spectrum antibacterial compound which is effective in the treatment of infections caused by gram-positive and gram-negative organisms that are commonly susceptible to sulfonamide therapy and which has been proven by laboratory and field experiments to be highly effective against diseases caused by Escherichia coli. Sulfachlorpyridazine has a rapid onset of action in several species of animals following both oral and parenteral administration. Sulfachlorpyridazine (brand name Vetisulid) is especially indicated for the treatment of diarrhea caused or complicated by E. coli (colibacillosis) in calves under 1 month of age: Vetisulid powder is also indicated for the treatment of colibacillosis in swine. Sulfachlorpyridazine is a dihydropteroate synthase inhibitor.

Sulfadimethoxine is a sulfonamide antibacterial used to treat many infections including treatment of respiratory, urinary tract, enteric, and soft tissue infections. It is most frequently used in veterinary medicine, although it is approved in some countries for use in humans. Sulfadimethoxine inhibits bacterial synthesis of folic acid (pteroylglutamic acid) from para-aminobenzoic acid. Sulfadimethoxine is approved in Russia for use in humans, including children, and has been successfully used there for more than 35 years and is available as an over-the-counter drug manufactured by a number of Russian pharmaceutical companies. In USA and Europe sulfadimethoxine is approved in a veterinary medicinal products. ANADA was approved by FDA in US in 1997 as an Over the Counter medicine for treatment of bovine respiratory disease complex (shipping fever complex) and bacterial pneumonia associated with Pasteurella Spp. Sensitive to sulfadimethoxine; necrotic pododermatitis (foot rot) and calf diphtheria caused by Fusobacterium necrophorum (Sphaerophorus necrophorus) sensitive to sulfadimethoxine. Bioequivalence for this generic animal drug, Sulfadimethoxine Injection 40%, was established by demonstration of chemical equivalence to the pioneer product, Hoffmann-La Roche's Albon® Injection 40% (NADA 041-245).