What to Know About Azithromycin

A Common Antibiotic for Treating Bacterial Infections

Azithromycin is a versatile antibiotic used to treat a wide variety of bacterial infections, including those affecting the lungs, skin, and gastrointestinal system, as well as a number of sexually transmitted infections (STIs). It belongs to a class of medications called macrolide antibiotics and is derived from a similarly named antibiotic, erythromycin. It works by interfering with a bacterium's ability to produce proteins, thus inhibiting growth. Azithromycin is available as a tablet or liquid to be taken orally, an injectable solution, and eye drops.

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Brand Names of Azithromycin

  • Zithromax
  • Zithromax Single Dose Packets
  • Zithromax Tri-Paks
  • Zithromax Z-Paks
  • Zmax (an extended-release formulation)


Azithromycin is used to treat and prevent many different types of infections. They include:

Azithromycin also is used prophylactically to prevent heart infection in people having dental or other procedures and to prevent STIs in victims of sexual assault.

Azithromycin is often prescribed as an alternative to penicillin for people who are allergic to it.

Off-Label Uses

Azithromycin sometimes is prescribed to treat moderate to severe acne. It also may be administered to children in intensive care. Azithromycin also has been investigated in combination with hydroxychloroquine to treat COVID-19, however it has not been shown to be effective.

Before Taking

A healthcare provider may prescribe azithromycin if you're showing signs of an infection such as fever, chills, and fatigue or pain at the infection site. They also may wait until after you've been tested for and diagnosed with a specific infection. In many cases, azithromycin will be the first antibiotic prescribed for an infection.

Be aware before you take azithromycin that it is the generic name of the drug and so you may be prescribed a brand-name version of this drug, depending on your doctor's preference and your specific infection.

It's also important for your practitioner to know certain details about your medical history that may affect whether azithromycin is the best antibiotic for you. Tell them if you have ever had an allergic reaction to azithromycin. Also share the names of all medications, vitamins, and supplements you currently take, if any. While some drugs pose minor interaction risks, others may contraindicate use.

Precautions and Contraindications

Precautions should be taken for people who have:

  • Hepatic impairment
  • Arrythmia
  • Bradycardia (low heart rate)
  • Recent heart attack
  • Older age

Azithromycin is strongly contraindicated in certain circumstances. If any apply to you and a healthcare provider who isn't familiar with your medical history wants to prescribe azithromycin for you, tell them so they can give you a safer alternative. The contraindications for azithromycin include:

Azithromycin is commonly used during pregnancy, however it is always a idea to inform your doctor if you are pregnancy.

Because azithromycin is so widely used, it is one of many antibiotics for which antibiotic resistance may be an issue, meaning it may not be fully effective against certain infections, including community-acquired pneumonia, ear infections, acute sinusitis, and methicillin-resistant Staphylococcus aureus (MRSA), a superbug with broad antibacterial resistance.


A typical course of azithromycin runs for three to 10 days, depending on the type of infection being treated. The most common dosage on day one is 500 milligrams (mg) in a single dose, which might come as a pill, a liquid, or a dry powder to which water must be added, followed by 250 mg orally once a day on days 2 to 5.

Zmax, an extended release suspension, is taken one time, within 12 hours of the prescription being filled.

All listed dosages are according to the drug manufacturer. Check your prescription and talk to your healthcare provider to make sure you are taking the right dose for you.

How to Take and Store

With the exception of Zmax, which is best taken on an empty stomach (at least one hour before or two hours after a meal), azithromycin can be taken with or without food. Follow your doctor's instructions as well as those on the label. Do not take more or less than what has been prescribed.

Take azithromycin until you finish the prescription, even if you feel better. If you stop taking azithromycin too soon or skip doses, your infection may return, allowing the bacteria to become resistant to antibiotics.

As with all medications, store in a cool, dry place, out of sight and out of reach of children.

Side Effects

As with any medication, azithromycin can cause side effects.


Many common side effects are related to the digestive system, but most are mild and should pass after your course of treatment is finished.

  • Nausea
  • Diarrhea
  • Vomiting
  • Stomach pain
  • Headache


Immediately stop taking azithromycin and seek medical attention if you experience the following:

  • Fast, pounding, or irregular heartbeat
  • Faintness or dizziness
  • Itching, hives, rash, or peeling
  • Pus-filled sores
  • Yellow eyes or pink and swollen eyes
  • Wheezing or difficulty breathing or swallowing
  • Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, lower legs, or skin
  • Severe diarrhea (watery or bloody stools) and stomach cramps occurring up to two months or more after treatment
  • Extreme fatigue or lack of energy
  • Unusual bleeding or bruising
  • Loss of appetite
  • Pain in the upper right part of the abdomen
  • Flu-like symptoms
  • Dark urine
  • Unusual muscle weakness or difficulty with muscle control

Warnings and Interactions

Azithromycin is widely used and is a common substitute for people who are allergic to other antibiotics. It's largely regarded as safe but there are some can interact with certain medications and other substances.

  • Antacids: Do not take azithromycin simultaneously with those containing aluminum hydroxide or magnesium hydroxide such as Maalox, Mylanta, or Tums. Ask your healthcare provide or pharmacist how many hours before or after you take azithromycin you may take these medications. The extended-release suspension may be taken at any time with antacids.
  • Certain blood thinners and drugs taken for irregular heartbeat: Your practitioner may need to change the doses of your medications or monitor you carefully for side effects if you take: Coumadin, Jantoven (warfarin); Colcrys, Gloperba (colchicine); Neoral, Sandimmune (cyclosporine); Lanoxin (digoxin); D.H.E. 45, Migranal (dihydroergotamine); Ergomar (ergotamine); Cordarone, Pacerone (amiodarone); Tikosyn (dofetilide): Procanbid (procainamide); Betapace, Sorine, (quinidine, and sotalol); Viracept (nelfinavir); Dilantin (phenytoin); or terfenadine (not available in the U.S.).
  • Alcohol: Drinking while on azithromycin may increase side effects.

Frequently Asked Questions

  • What is a Z-Pak?

    A Z-Pak is a five-day course of the antibiotic Zithromax (azithromycin) distributed in a blister pack. A Z-Pak contains six 250 mg tablets. Take two tablets the first day and one tablet a day for the next four days. 

  • What does azithromycin treat?

    Azithromycin is an antibiotic used to treat bacterial infections such as respiratory tract infections, Lyme disease, ear infections, conjunctivitis, and skin infections. It is also sometimes prescribed as a preventive measure prior to dental procedures. 

  • Can you take azithromycin if you are allergic to penicillin?

    Yes. Azithromycin is a macrolide antibiotic that treats a wide spectrum of bacteria. It is commonly prescribed in place of penicillin for people with a penicillin allergy.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. MedlinePlus. Azithromycin. Apr 15, 2020.

  2. Oshikoya KA, Wharton GT, Avant D, et al. Serious adverse events associated with off-label use of azithromycin or fentanyl in children in intensive care units: A retrospective chart review. Paediatr Drugs. 2019;21(1):47-58. doi:10.1007/s40272-018-0318-9

  3. Gbinigie K, Frie K. Should azithromycin be used to treat COVID-19? A rapid review. BJGP Open. 2020;4(2). doi:10.3399/bjgpopen20X101094

  4. Rao GA, Mann JR, Shoaibi A, et al. Azithromycin and levofloxacin use and increased risk of cardiac arrhythmia and deathAnn Family Med. 2014;12(2):121-127. doi:10.1370/afm.1601

Additional Reading

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.