Clarithromycin is an antibacterial drug which is used either in combination with lansoprazole and amoxicillin (Prevpac), in combination with omeprazole and amoxicillin (Omeclamox) or alone (Biaxin) for the treatment of broad range of infections. The drug exerts its action by binding to 23s rRNA (with nucleotides in domains II and V). The binding leads to the protein synthesis inhibition and the cell death.

Erythromycin ethylsuccinate (E.E.S.®, ERY-PED®) is an ester of erythromycin base and succinic acid. It is suitable for oral administration. Erythromycin is a macrolide antibiotic, produced by Saccharopolyspora erythraea (formerly Streptomyces erythraeus). It acts primarily as a bacteriostatic agent. In sensitive organisms, it inhibits protein synthesis by binding to 50S ribosomal subunits. This binding process inhibits peptidyl transferase activity and interferes with translocation of amino acids during translation and assembly of proteins. Erythromycin does not affect nucleic acid synthesis.

Modithromycin (EDP-420, EP-013420, S-013420) is 6-11-bicyclic erythromycin derivative patented by Enanta Pharmaceuticals, Inc as an antibacterial agent. In preclinical studies, Modithromycin exhibited high levels of in vitro activities against N. gonorrhea, including isolates resistant to azithromycin, cefixime, ceftriaxone, spectinomycin, ampicillin, tetracycline, and ciprofloxacin. Modithromycin also has the good in vivo efficacy against S. pneumoniae and H. influenzae, which might be due to its lasting intracellular activity. In healthy adults, clinical trials Modithromycin shows long half-life and its high systemic exposure. Modithromycin was well tolerated, with no serious or severe adverse events reported, and no subject was discontinued from the study due to an adverse event. In 2005 Modithromycin was studied in phase II clinical trials but no further development reports were published.

Mitemcinal (GM-611), an erythromycin-derived prokinetic agent, was developed by Chuga as an agonist of the motilin receptor. Mitemcinal acts by a novel mechanism whereby it stimulates and promotes peristalsis in the stomach and other segments of the gastrointestinal tract. This drug was studied as a potential treatment for gastric motility disorder, as well as reflux esophagitis, non-ulcer dyspepsia, and diabetic gastroparesis. Mitemcinal was involved in phase II clinical trials in Patients with diabetic gastroparesis. Although gastroparetic symptoms improved with both mitemcinal and placebo, the prominent placebo effect was not statistically exceeded by mitemcinal. That is why the development of this drug has stalled. In addition, mitemcinal has been studied in phase II for the treatment of irritable bowel syndrome, but this study was also discontinued.

Lexithromycin is an early semi-synthetic erythromycin, prepared by reaction of the 9-keto moiety to methyl oxime. Lexithromycin has improved absorption in vivo over erythromycin due to increased hydrophopicity and pH stability. Like all erythromycins, lexithromycin shows broad spectrum antibacterial activity and acts by binding to the 30S and 50S ribosomal sub-units, blocking protein synthesis. Formulations containing lexithromycin were tested in clinical trials as treatment for HIV but were discontinued.

Berythromycin or erythromycin B (also known as 12-deoxyerythromycin A), an acid-stable co-metabolite of the antibiotic erythromycin A, exhibits broad-spectrum antibiotic activity. The antibacterial activity of erythromycin B is similar to that of erythromycin A, but after acid-treatment, resembling exposure to the stomach, erythromycin B substantially retains antibacterial activity, whereas erythromycin A does not. Erythromycin B played an integral part of the structure activity relationship studies of semi-synthetic erythromycins.