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Lexithromycin is a semisynthetic antibiotic derived from erythromycin . Lexithromycin has improved absorption in vivo over erythromycin due to increased hydrophopicity and pH stability. As with other macrolides, lexithromycin prevents protein synthesis by binding the ribosome at the polypeptide exit tunnel. Formulations containing lexithromycin were tested in clinical trials as treatment for HIV but were discontinued.

Lexithromycin is an early semi-synthetic erythromycin, prepared by reaction of the 9-keto moiety to methyl oxime. The structural change improves the pH stability profile and hydrophobicity of lexithromycin for better in vivo absorption. This same rationale was used to greater effect with roxithromycin and, as a result, lexithromycin was quickly superseded and has not been not extensively studied. Like all tetracyclines, lexithromycin shows broad spectrum antibacterial and antiprotozoan activity and acts by binding to the 30S and 50S ribosomal sub-units, blocking protein synthesis.

[1] E HUNT. Erythromycin A 11,12-methylene acetal.[J]. Journal of Antibiotics, 1988, 41 11: 1644-1648. DOI: 10.7164/antibiotics.41.1644