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.

Sulfamazone is a long-acting sulfonamide antibiotic with antipyretic properties. It is not approved by the FDA, but is marketed in Italy under tradename Marespin for the treatment of acute respiratory diseases; primary bacterial pharyngotonsillitis and tracheobronchitis or complications of the flu or other viral diseases of the upper respiratory tract.

Sulfametrole is a sulfonamide antibiotic used typically in combination with trimethoprim. Sulfametrole combined with trimethoprim could provide a choice for difficult-to-treat infections, particularly when administered intravenously. Sulfametrole/trimethoprim is an alternative sulphonamide/trimethoprim combination available in several EU countries, including Austria and the Netherlands. Sulphonamide/trimethoprim combination is the most active antibacterial but sulfametrole and sulfametrole/trimethoprim did not overcome resistance to sulfamethoxazole and sulfamethoxazole/trimethoprim in Enterobacteriaceae.

Sulphathiourea (Badional) is short acting sulfonamide, belongs to antibacterial drugs

Sulfamonomethoxine is a long-acting sulfonamide antibiotic. It is active against Streptococcus spp. (Including Streptococcus pneumoniae, Enterococcus spp.), Staphylococcus spp., Escherichia coli, Shigella spp., some strains of Proteus spp., Neisseria gonorrhoeae, Neisseria meningitides. Sulfamonomethoxine also active against Chlamydia spp., Toxoplasma gondii, Plasmodium. Rapidly absorbed from the gastrointestinal tract, it penetrates the BBB. The relatively low toxicity. Sulfamonomethoxine is a competitive inhibitor of dihydropteroate synthetase used to block the synthesis of folic acid. By preventing the production of folate in bacteria, the sulfonamide antibiotics ultimately suppress bacterial DNA replication.

Tetroxoprim is an inhibitor of bacterial dihydrofolate reductase. In combination with sulfadiazine (co-tetroxazine) it has been used for the treatment of susceptible bacterial infections.

Sulfamoxole is a sulfonamide antibacterial compound. Sulfamoxole is a competitive inhibitor of the bacterial enzyme dihydropteroate synthetase. Sulfamoxole alone or in combination with trimethoprim is used for the treatment of susceptible infections.