Pheneticillin (phenoxyethylpenicillin) is an oral penicillin used for the treatment of upper respiratory tract infections; lower respiratory tract infections; skin and soft tissue infections. Pheneticillin inhibits the synthesis of the cell wall by inhibiting the penicillin binding proteins (PBPs) function. It is well absorbed from the gastrointestinal tract. It reaches the pleural and peritoneal cavities but doesn’t cross the blood-brain barrier. Diarrhea has sometimes occurred with therapeutic doses in man.

Rolitetracycline, launched in the late 1950s, was the first of the semi -synthetic tetracyclines. Rolitetracycline is formed by a Mannich condensation of formaldehyde and pyrrolidine with tetracycline. Rolitetracycline is a pro -drug of tetracycline, in which the pyrrolidine moiety improves bioavailability compared with tetracycline. Rolitetracycline has broad spectrum Gram positive activity in vivo, but pH instability limits use to parenteral administration. Rolitetracycline passively diffuses through porin channels in the bacterial membrane and reversibly binds to the 30S ribosomal subunit, preventing binding of tRNA to the mRNA-ribosome complex, and thus interfering with protein synthesis.

Troleandomycin (also known Triacetyl-oleandomycin and having brand name Tao) is a macrolide antibiotic which used to for the treat of infections of the upper and lower respiratory tract: such as tonsillitis, bronchitis, sinusitis, and pneumonia. However, the brand name Tao was discontinued. Troleandomycin acts by penetrating the bacterial cell membrane and reversibly binding to the 50 S subunit of bacterial ribosomes or near the "P" or donor site so that binding of tRNA (transfer RNA) to the donor site is blocked. Translocation of peptides from the "A" or acceptor site to the "P" or donor site is prevented, and subsequent protein synthesis is inhibited.

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).

Oleandomycin is a macrolide antibiotic, which was first described under the designation P.A.105 by Sobin, English, and Celmer (1954-5). Later it appeared on the market under three names and in two forms: as pure oleandomycin ("matromycin," Pfizer; "romicil," Hoffmann-La Roche) and as a mixture with twice its weight of tetracycline ("sigmamycin," Pfizer). Oleandomycin can be employed to inhibit the activities of bacteria responsible for causing infections in the upper respiratory tract much like Erythromycin can. Both can affect staphylococcus and enterococcus genera. Oleoandomycin is reported to inhibit most gram-positive bacteria, but has only a slight inhibiting effect on gram-negative bacteria, rickettsiae, and larger viruses. The spectrum of activity on micro-organisms is therefore wider than that of penicillin and streptomycin, but narrower than that of chloramphenicol and the tetracyclines. Oleandomycin is approved as a veterinary antibiotic in some countries. It has been approved as a swine and poultry antibiotic in the United States. However, it is currently only approved in the United States for production uses. Oleandomycin is a bacteriostatic agent. Like erythromycin, oleandomycin binds to the 50s subunit of bacterial ribosomes, inhibiting the completion of proteins vital to survival and replication. It interferes with translational activity but also with 50s subunit formation. However, unlike erythromycin and its effective synthetic derivatives, it lacks a 12-hydroxyl group and a 3-methoxy group. This change in structure may adversely affect its interactions with 50S structures and explain why it is a less powerful antibiotic.

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.

Chloramphenicol is a broad-spectrum antibiotic that was first isolated from Streptomyces venezuelae in 1947. The drug was subsequently chemically synthesized. It has both a bacteriostatic and bactericidal effect; in the usual therapeutic concentrations it is bacteriostatic. Chloramphenicol is used for the treatment of serious gram-negative, gram-positive, and anaerobic infections. It is especially useful in the treatment of meningitis, typhoid fever, and cystic fibrosis. It should be reserved for infections for which other drugs are ineffective or contraindicated. Chloramphenicol, a small inhibitor of bacterial protein synthesis, is active against a variety of bacteria and readily enters the CSF. It has been used extensively in the last decades for the treatment of bacterial meningitis. In industrialized countries, chloramphenicol is restricted mostly to topical uses because of the risk of induction of aplastic anemia. However, it remains a valuable reserve antibiotic for patients with allergy to β-lactam antibiotics or with CNS infections caused by multiresistant pathogens.

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.