azithromycin

Azithromycin is a macrolide antibiotic used to treat bacterial infections. It works by binding to the 50S subunit of the bacterial ribosome, inhibiting protein synthesis. It is generally bacteriostatic but can be bactericidal at high concentrations for some organisms.

Common indications include respiratory infections, skin and soft tissue infections, acute otitis media, and some sexually transmitted infections (notably Chlamydia trachomatis). It is also used for certain traveler’s diarrhea. For gonorrhea, it is used in combination with ceftriaxone due to resistance patterns.

Administration and pharmacokinetics: Available orally as tablets or suspension, and by intravenous infusion in hospital. It has a long elimination half-life (~40-68 hours) and extensive tissue distribution, allowing once-daily dosing. Metabolism occurs in the liver; most of the drug is excreted in bile; renal excretion is limited.

Safety: Common adverse effects include nausea, diarrhea, and abdominal pain. More serious risks include QT interval prolongation and rare arrhythmias, particularly with other QT-prolonging drugs or electrolyte abnormalities. It may cause C. difficile-associated diarrhea. Azithromycin is generally considered safe in pregnancy (category B). Caution in patients with liver disease; breastfeeding generally allowed with caution.

Resistance and stewardship: Resistance has emerged in some pathogens; guidelines emphasize appropriate use and stewardship to preserve efficacy.