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).

Sulfamethizole is an oral antiobiotic, which was used against urinary tract infections under the name Thiosulfil. Sulfamethizole blocks bacterial growth by inhibiting folic acid synthesis via enzyme called dihydropteroate synthase. The drug is no longer marketed in the USA.

Sulfisomidine (INN), also known as sulphasomidine (BAN until 2003), is a sulfonamide antibacterial. It’s used in the treatment, control, prevention, and improvement of the following conditions and symptoms: Lower urinary tract infections; Meningococcal meningitis; Streptococcal pharyngitis; Gum infection; Bacillary dysentery.

Sulfisoxazole is a sulfonamide antibacterial antibiotic. The sulfonamides are synthetic bacteriostatic antibiotics with a wide spectrum against most gram-positive and many gram-negative organisms. However, many strains of an individual species may be resistant. Sulfisoxazole acetyl in combination with erythromycin ethylsuccinate is used for treatment of ACUTE OTITIS MEDIA in children that is caused by susceptible strains of Haemophilus influenzae. Sulfisoxazole acetyl is a prodrug of sulfisoxazole. Acetyl group is added to make the drug poorly water soluble, and is hydrolyzed in vivo to the active drug. Sulfisoxazole and its acetylated metabolites are excreted primarily by the kidneys through glomerular filtration. Sulfisoxazole is a competitive inhibitor of the enzyme dihydropteroate synthetase. It inhibits bacterial synthesis of dihydrofolic acid by preventing the condensation of the pteridine with para-aminobenzoic acid (PABA), a substrate of the enzyme dihydropteroate synthetase. The inhibited reaction is necessary in these organisms for the synthesis of folic acid

Sulfamerazine is a sulfonamide antibiotic, which acts by inhibiting folic acid synthesis in bacterias. The primary target of sulfamerazine is believed to be dihydropteroate synthetase. Sulfamerazine (in comination with Sulfadiazine and Sulfamethazine) was used in the US under different names, including the earliest brand of Neotrizine. Nowdays, the drugs containing sulfamerazine are no longer available for use in humans in the US, however, they may be prescribed for veterinary purposes.

Sulfathiazole is a short-acting sulfonamide with properties similar to those of sulfamethoxazole. It is now rarely used systemically due to its toxicity. Sulfathiazole is used with other sulfonamides, usually sulfabenzamide and sulfacetamide, in preparations for the topical treatment of vaginal infections and is also used with other drugs in the treatment of skin infections. Sulfathiazole sodium has been applied topically with other drugs in the treatment of eye infections. Sulfathiazole interferes with nucleic acid synthesis in microorganisms by blocking the conversion of p-aminobenzoic acid to the coenzyme dihydrofolic acid.It has properties similar to sulfamethoxazole.

Sulfapyridine is a competitive inhibitor of the bacterial enzyme dihydropteroate synthetase. It was used to treat of infections in humans in particular, dermatitis herpetiformis (Duhring's disease), a skin problem, but that usage was discontinued by manufacturer. It is also known, that sulfapyridine is one of the two primary metabolite of the anti-inflammatory drug salicylazosulfapyridine.

Sulfaquinoxaline is a veterinary drug, which can be given to animals to treat coccidiosis and Acute Fowl cholera. It has often used in combinations with others drugs. It had its origins in the chemical synthetic program that sprang from the introduction of sulfonamide drugs into human medicine in the 1930s. The program was sustained through the years of World War II despite declining clinical use of that chemical class. Several sulfa drugs were known to be active against the sporozoan parasite (Plasmodium spp.) that causes malaria, but were not satisfactory in clinical practice. A sulfonamide that had a long plasma half-life would ipso facto be considered promising as an antimalarial drug. Sulfaquinoxaline, synthesized during the war, was such a compound. It proved too toxic to be used in human malaria, but was found to be a superior agent against another sporozoan parasite, Eimeria spp., the causative agent of coccidiosis in domestic chickens. In 1948 sulfaquinoxaline was introduced commercially as a poultry coccidiostat. The action mechanism of sulfaquinoxaline is to inhibit the dihydrofolate synthetase to encumber the nucleate synthesis of bacterium and coccidian its active peak to coccidian is at the second schizont stage (the fourth day of coccidial life cycle), so it will not affect the anti-coccidial immunity in chicken.