Amoxil vs Zithromax
Two of the most prescribed antibiotics, covering different bacteria over different course lengths — and why they are not interchangeable.
At a glance
Key differences
- Same class. Both Amoxil and Zithromax are antibiotics, so they work through the same broad mechanism. Differences between them tend to be about dosing, route, how selective they are, and side effects rather than what they target.
- Time on the market. Amoxil was first approved by the FDA in 1974, Zithromax in 1991. That gives Amoxil roughly 17 more years of real-world use and long-term safety data.
- Who markets them. Amoxil is marketed by GlaxoSmithKline; Zithromax by Pfizer.
What each one treats
To reduce the development of drug-resistant bacteria and maintain the effectiveness of Amoxicillin and other antibacterial drugs, Amoxicillin for Oral Suspension should be used only to treat infections that are proven or strongly suspected to be caused by bacteria. 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. Amoxicillin for Oral Suspension is indicated in the treatment of infections due to susceptible (ONLY β-lactamase–negative) isolates of the designated bacteria in the conditions listed below: 1.1 Infections of the ear, nose, and throat - due to Streptococcus species.(α- and β-hemolytic isolates only), Streptococcus pneumoniae, Staphylococcus spp., or Haemophilus influen…
ZITHROMAX is a macrolide antibacterial drug indicated for the treatment of the following infections caused by designated susceptible microorganisms: • Community-acquired pneumonia in adults ( 1.1 ) • Pelvic inflammatory disease in adults ( 1.2 ) To reduce the development of drug-resistant bacteria and maintain the effectiveness of ZITHROMAX and other antibacterial drugs, ZITHROMAX should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. ( 1.3 ) 1.1 Community-Acquired Pneumonia ZITHROMAX is indicated for the treatment of adult patients with community-acquired pneumonia due to the following susceptible microorganisms: Chlamydophila pneumoniae, Haemophilus influenzae, Legionella pneumophila, Moraxella catarrhalis, Mycoplasma pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae in patients who require initial in…
How each one works
A first-line antibiotic for many common bacterial infections.
12.1 Mechanism of Action Azithromycin is a macrolide antibacterial drug [see Microbiology (12.4) ]
Read more
Which medicine is right for a given person depends on their diagnosis, other conditions, other medicines, kidney and liver function, pregnancy, and cost or reimbursement — none of which this page knows. Two drugs in the same class are not automatically interchangeable. Never start, stop or switch a prescription medicine on the basis of a web page; that decision belongs to you and your clinician or pharmacist.
How this page is built
The facts on this page are pulled directly from official U.S. FDA datasets — they are not written from memory. Each field below names the dataset it came from, so you can check it yourself.
- FDA Drug Label (openFDA) ↗ Indications, mechanism of action and pharmacologic class
- Drugs@FDA ↗ First FDA approval date and the company holding the application
- FDA Drug Shortage Database ↗ Current US supply / shortage status
Plain-English summaries and drug-class explainers are written and reviewed by Sreepriya Prasannan (MSc Digital Transformation of Life Sciences (Innopharma Education / Griffith College); MSc & BSc Botany). Data is retrieved automatically from the sources above and cross-checked with AI-assisted verification (Anthropic's Claude) — brand and generic names are matched against the exact FDA product record so that a combination product or a different formulation cannot be mistaken for the drug on this page. An editor reviews the result before publication. We describe this in full in our editorial standards and corrections policy. The FDA data on this page was last retrieved on 11 Oct 2026. How every register is built: methodology · fixes we have made: corrections log.