Methacycline is a tetracycline antibiotic. Similar to other tetracyclines, it has a wide spectrum of antimicrobial action. It is active against most Gram-positive bacteria (pneumococci, streptococci, staphylococci) and Gram-negative bacteria (E. coli, salmonella, shigella, etc.), and towards agents causing onithosis, psittacosis, trachoma, and some Protozoa. Like other tetracyclines, the general usefulness of methacycline has been reduced with the onset of bacterial resistance. Methacycline inhibits the binding of aminoacyl-tRNA to the mRNA-ribosome complex. Methacycline inhibits cell growth by inhibiting translation. It binds to the 16S part of the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. Methacycline is mostly used for the treatment of acute bacterial exacerbations of chronic bronchitis.

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.

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.

Apicycline is a semisynthetic antibiotic. It belongs to the tetracyclines.

Clomocycline is the approved name of a methylol derivative of chlortetracycline. Clomocycline is a tetracycline antibiotic that is commonly prescribed by medical doctors for infections and to treat acne. It may also be used to treat urinary tract infections, gum disease, and other bacterial infections such as gonorrhea and chlamydia. Clomocycline is also used commonly as a prophylactic treatment for infection by Bacillus anthracis (anthrax). It is also effective against Yersinia pestis and malaria and is also prescribed for the treatment of Lyme disease. Clomocycline inhibits cell growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. The binding is reversible in nature. Clomocycline is lipophilic and can easily pass through the cell membrane or passively diffuses through porin channels in the bacterial membrane. This drug has been reported to be noticeably free of side-effects such as nausea, vomiting, and diarrhea.

Pipacycline is a semi-synthetic tetracycline formed by a Mannich condensation of formaldehyde and 4-hydroxyethyl piperazine with tetracycline. The introduction of the piperazine improves bioavailability, but Mannich bases are pro-drugs, converting back to the parent compound. Pipacycline is used commercially as a salt in combination with penicillin V for parenteral use (penimepicycline). Penimepicycline exerts a bactericidal action on the streptococci, and a bacteriostatic action on various gram-positive and gram-negative bacilli, as well as on the penicillin-resistant staphylococci.

Lymecycline is a tetracycline broad-spectrum antibiotic marketed by the pharmaceutical company Galderma. It is approximately 5,000 times more soluble than tetracycline base and is unique amongst tetracyclines in that it is absorbed by an active transport process across the intestinal wall, making use of the same fast and efficient mechanism by which carbohydrates are absorbed. Lymecycline's side effects can include rash, headache, diarrhoea, ulcerative colitis, nausea, vomiting, dermatitis, dysphasia, inflammation of the liver, hypersensitive reactions, and visual disturbances. When taken for a long period of time, it can cause reflux oesophagitis.

Rolitetracycline nitrate is an antibiotic formed by N-aminomethylation of the carboxamide group of tetracycline. 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. It is formulated for intravenous or intramuscular injections and is used in cases requiring high concentrations or when oral administration is impractical. In combinations with chloramphenicol and colistin, it is used as the eye drops for the treatment of external eye infections such as catarrhal conjunctivitis, purulent, trachoma, blepharitis, blepharoconjunctivitis, bacterial keratitis, septic corneal ulcers.

Neomycin is an aminoglycoside antibiotic found in many topical medications such as creams, ointments, and eye drops. In vitro tests have demonstrated that neomycin is bactericidal and acts by inhibiting the synthesis of protein in susceptible bacterial cells. It is effective primarily against gram-negative bacilli but does have some activity against gram-positive organisms. Neomycin is active in vitro against Escherichia coli and the Klebsiella-Entero. Topical uses include treatment for superficial eye infections caused by susceptible bacteria (used in combination with other anti-infective), treatment of otitis externa caused by susceptible bacteria, treatment or prevention of bacterial infections in skin lesions, and use as a continuous short-term irrigant or rinse to prevent bacteriuria and gram negative rod bacteremia in bacteriuria patients with indwelling catheters. May be used orally to treat hepatic encephalopathy, as a perioperative prophylactic agent, and as an adjunct to fluid and electrolyte replacement in the treatment of diarrhea caused to enter pathogenic E. coli (EPEC). Neomycin sulfate has been shown to be effective adjunctive therapy in hepatic coma by reduction of the ammonia forming bacteria in the intestinal tract. The subsequent reduction in blood ammonia has resulted in neurologic improvement. To reduce the development of drug-resistant bacteria and maintain the effectiveness of Neomycin Sulfate Oral Solution and other antibacterial drugs, susceptible bacteria should use Neomycin Sulfate Oral Solution only to treat or prevent infections that are proven or strongly suspected to be caused. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Neomycin binds to four nucleotides of 16S rRNA and a single amino acid of protein S12. This interferes with decoding site near nucleotide 1400 in 16S rRNA of 30S subunit. This region interacts with the wobble base in the anticodon of tRNA. This leads to interference with the initiation complex, misreading of mRNA so incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides and the breakup of polysomes into nonfunctional monosomes

Sarecycline (SC1401, WC3035) is a novel, once-daily, tetracycline-derived compound being developed by Paratek Pharmaceuticals and Allergan (previously Actavis) for use in the treatment of acne and rosacea. In preclinical studies, Sarecycline possesses favorable anti-inflammatory activity, plus narrow-spectrum antibacterial activity relative to other tetracycline-derived molecules. Sarecycline has been used in Phase III clinical trials studying the treatment of Acne Vulgaris. The primary objective was to evaluate the efficacy and safety of oral Sarecycline 1.5 mg/kg per day compared to placebo in treating inflammatory acne lesions in subjects with moderate to severe acne. Sarecycline was statistically significantly superior to placebo with respect to primary efficacy endpoints. The most common adverse events (>2%) reported in the sarecycline group were nausea (3.2%), nasopharyngitis (2.8%), and headache (2.8%). The rate of discontinuation due to adverse events among sarecycline-treated patients in the two studies combined was 1.4%.