azithromycin
Azithromycin (Zithromax) is an oral macrolide antibiotic used for mild to moderate infections caused by susceptible bacteria, including prophylaxis and treatment of disseminated Mycobacterium avium complex (MAC) disease in persons with advanced HIV infection. It works by binding to bacterial ribosomes and stopping production of proteins the bacteria need to grow and spread. It is not effective against viral infections.
This page is based on FDA prescribing information for azithromycin tablets, cross-checked with MedlinePlus; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Bacteria are like tiny factories that build proteins to stay alive and multiply. Azithromycin jams the assembly line by sitting on one of the factory's machines (the 50S ribosome). With the machine blocked, the bacteria can no longer make the proteins they need, so they stop growing and the immune system can clear the infection.
In simple terms
Azithromycin is a macrolide antibiotic. It works by stopping bacteria from making the proteins they need to grow and multiply. It does this by attaching to a part of the bacteria's protein-making machinery called the 50S ribosome. When the ribosome is blocked, the bacteria cannot produce essential proteins and their growth slows or stops. Azithromycin is taken by mouth to treat mild to moderate bacterial infections and to prevent or treat disseminated MAC disease in people with advanced HIV infection. It does not work against colds, flu, or other viral infections.
In depth
Azithromycin is a 15-membered azalide macrolide antibiotic. It binds reversibly to the 23S rRNA component of the bacterial 50S ribosomal subunit, blocking the translocation step of peptide elongation. This inhibits bacterial protein synthesis and produces bacteriostatic activity against susceptible organisms. Azithromycin concentrates within phagocytes and macrophages, achieving high tissue levels that contribute to its prolonged post-antibiotic effect. It is indicated for mild to moderate infections caused by designated susceptible bacteria and for prophylaxis and treatment of disseminated Mycobacterium avium complex (MAC) disease in persons with advanced HIV infection.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How azithromycin blocks the factory's protein machines
- Bacteria are like tiny factories that build proteins to stay alive and multiply.
- Azithromycin is a macrolide antibiotic.
- Azithromycin jams the assembly line by sitting on one of the factory's machines (the 50S ribosome).
- When the ribosome is blocked, the bacteria cannot produce essential proteins and their growth slows or stops.
Target: Bacterial 50S ribosomal subunit
Azithromycin binds reversibly to the 23S rRNA of the bacterial 50S ribosomal subunit, blocking the translocation step of protein synthesis and thereby inhibiting bacterial growth.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Treatment of mild to moderate infections caused by susceptible bacteria
- Prophylaxis of disseminated Mycobacterium avium complex (MAC) disease in persons with advanced HIV infection
- Treatment of disseminated MAC infections in persons with advanced HIV infection (in combination with ethambutol)
Approved uses in United States
MedlinePlus- Treatment of infections caused by bacteria
- Treatment and prevention of disseminated Mycobacterium avium complex (MAC) infection
Official sources
The statements on this page trace back to these records.
- U.S. Food and Drug Administration: azithromycin prescribing information
U.S. Food and Drug Administration
- MedlinePlus: azithromycin
MedlinePlus, U.S. National Library of Medicine
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.