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.

Iclaprim is an investigational broad-spectrum diaminopyrimidine antibiotic in development for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). Iclaprim acts on bacterial cells by competitively inhibiting dihydrofolate reductase (DHFR), a key enzyme in the folate cycle; the same mode of inhibition is exerted by trimethoprim. Iclaprim resistance is mainly determined by point mutations in the dfr gene as studied in S. aureus and S. pneumoniae. Surveillance studies demonstrate that the spectrum of activity of iclaprim includes many organisms indicated in cSSSI including S. aureus and S. pyogenes. Iclaprim is bactericidal in vitro, generally at concentrations equal to the MIC that are maintained in human plasma for several hours after a therapeutic dose. Bactericidal activity is primarily time-dependent and concentration independent. Due to its structural similarity with trimethoprim, iclaprim is synergistic with sulfonamides against a broad spectrum of bacterial species. The antimicrobial mechanism of action of iclaprim is mediated by competitive inhibition of bacterial DHFR, the same mode of inhibition exerted by TMP. The activity of iclaprim against TMP-R mutants of S. aureus and S. pneumoniae is attributable to additional hydrophobic interaction between iclaprim and the enzyme. The same mechanism of action of iclaprim, competitive inhibition with the natural substrate DHF, is seen against both TMP-S and -R enzymes. Iclaprim is well suited for use as a first-line empiric monotherapy in patients with ABSSSI who are comorbid with renal impairment for the following reasons. n July 2015, the U.S. Food and Drug Administration, or FDA, designated the IV formulation of iclaprim as a Qualified Infectious Disease Product (QIDP) for ABSSSI and HABP. QIDP status grants iclaprim regulatory Fast Track designation, Priority Review and, if approved, a five-year extension to the statutory market exclusivity period in the United States, resulting in 10 years of market exclusivity from the date of approval.

Sulfaperine is a long-acting sulfonamide antibiotic.

Brodimoprim, is a new 2,4-diaminobenzylpyrimidine that , that selectively inhibits bacterial and resistance plasmid dihydrofolate reductases to a similar or greater extent than trimethoprim. Brodimoprim is two to three times more potent than trimethoprim and has more than 100-fold the affinity for dihydrofolate reductase with analogous enzymatic activity of eukaryotic cells. Brodimoprim’s in vitro activity is similar to that of trimethoprim. Brodimoprim is decidedly superior to trimethoprim in vivo in the mouse acute infection model, due to its much longer elimination half-life and better tissue diffusion. Acute and subacute toxicity tests in traditional laboratory animals show that there is little difference between brodimoprim and trimethoprim. Brodimoprim had no teratogenic or embryotoxic effects and mutagenic analysis was negative

Sulfametomidine (or sulfamethomidine) is a sulfonamide antibacterial with a broad spectrum of activity; it’s an inhibitor of dihydrofolate reductase.