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Overview: Azithromycin is an antibiotic that is used to treat certain bacterial infections. It works by stopping certain types of bacteria from making proteins they need to grow and multiply. Common side effects include nausea and vomiting, diarrhea, and stomach pain. Call your health care provider right away if you have diarrhea that does not go away or is bloody, if you have changes in your heart rate or rhythm or you faint, or if you have light-colored poop or dark-colored pee. Azithromycin comes in several forms, including a tablet or liquid that is taken by mouth and an injection that is given by a health care provider.

Uses

What is azithromycin used for?

Azithromycin is an antibiotic that is commonly used for the following infections caused by certain bacteria.

Azithromycin may not be the right medicine for some of the infections listed above, depending on which germs are causing the infection. Bacteria in some locations may have developed resistance to azithromycin, which will make  it not work as well.

Azithromycin may also be used for other conditions as determined by your health care provider.

Other forms of azithromycin are available for use in the eyes. See AzaSite (azithromycin) for more information.

How does azithromycin work (mechanism of action)?

Azithromycin stops certain types of bacteria from making proteins they need to grow and multiply.

How is azithromycin supplied (dosage forms)?

Brands and other names

  • Zithromax
  • Zithromax Tri-Pak
  • Zithromax Z-Pak
  • Zmax

Dosage forms and strengths

  • 250 mg oral tablets
  • 500 mg oral tablets
  • 600 mg oral tablets
  • 100 mg/5 mL for oral suspension
  • 200 mg/5 mL for oral suspension
  • 1 g/5 mL for oral suspension

Azithromycin is also available in injectable forms that are given by a health care provider.

How should I store azithromycin?

Oral Tablet. Most azithromycin oral tablets should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). They can be exposed to temperatures between 59 F and 86 F (15 C and 30 C), for shorter periods of time, such as when transporting them. Store in a cool, dry place, in a tightly closed container.

Oral Liquid. Azithromycin oral liquid should be stored at room temperature or in the refrigerator, between 41 F and 86 F (5 C and 30 C), and used within 10 days. You should not freeze it. Safely throw away any unused portion after the full treatment is finished.

Side Effects

What are the most common side effects of azithromycin?

The most common side effects of azithromycin are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea and vomiting
  • Diarrhea
  • Stomach pain

There may be other side effects of azithromycin that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of azithromycin?

While less common, the most serious side effects of azithromycin are described below, along with what to do if they happen.

Severe Allergic Reactions. Azithromycin can cause allergic reactions, which can be serious. Stop using azithromycin and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Angioedema. Azithromycin may cause a rare reaction called angioedema. The usual symptoms of this reaction include swelling of the lips, face, tongue, or throat. Stop using the medicine and call your health care provider right away if you have this type of swelling. If you are having trouble breathing, get medical attention right away.

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking azithromycin. Call your health care provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Heart Rhythm Changes. Azithromycin may cause a rare, dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk of this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium, or who take some medicines for other heart rhythm problems. Tell your health care provider right away if you faint or have changes in your heart rate or rhythm, such as fast or skipping heartbeat.

Antibiotic-Associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or C. diff, can happen in your gut with many types of antibiotics, including azithromycin. This can cause a condition known as antibiotic-associated diarrhea and can happen even up to 2 months after stopping the antibiotic. Call your health care provider right away if you have any of the following symptoms of this condition.

  • Watery diarrhea
  • Diarrhea that does not go away
  • Blood in your stool (poop)
  • Severe stomach cramps
  • Fever that starts after you start or finish the medicine

Infantile Hypertrophic Pyloric Stenosis. A condition called infantile hypertrophic pyloric stenosis can happen in babies who are less than 6 weeks old after being given azithromycin. This condition makes it harder for food to move from the baby’s stomach into their intestines, causing vomiting and trouble keeping food down. Call your health care provider right away if your baby throws up or is irritable after feeding.

Warnings & Precautions

Who should not use azithromycin?

Allergies to Ingredients. People who are allergic to any of the following should not use azithromycin.

  • Azithromycin
  • Erythromycin
  • Zithromax, Zithromax Tri-Pak, or Zithromax Z-pak
  • Zmax
  • Any other medicine known as a macrolide
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific azithromycin products they stock.

Liver Problems. Azithromycin should not be used if you have had problems with your liver when taking azithromycin in the past. If there is a concern about the health of your liver, your health care provider may do tests to see if it is working well enough to take this medicine.

What should I know about azithromycin before using it?

Do not use azithromycin unless it has been prescribed to you by a health care provider. Use it as prescribed.

Do not share azithromycin with other people, even if they have the same condition as you. It may harm them.

Keep azithromycin out of the reach of children. Since the oral liquid may be kept in a refrigerator, take special precautions to keep it away from children who also use the refrigerator.

People who are over 60 years old can be at greater risk for some side effects from azithromycin. Talk to your health care provider about your risks if you are in this age group.

Azithromycin only treats certain infections caused by bacteria. It will not work for infections caused by viruses, such as the common cold, the flu, or coronavirus. It also will not work for any other infections that are not caused by certain bacteria. Taking azithromycin or any other antibiotic when it is not needed may cause the antibiotic to not work for bacterial infections in the future.

If you are taking azithromycin oral liquid, use the measuring device that comes with your prescription to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist if you are not sure what measuring device to use. Shake the liquid well before drawing up each dose.

What should I tell my health care provider before using azithromycin?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if azithromycin is right for you.

In particular, make sure that you discuss any of the following.

Heart Problems. Tell your health care provider if you or anyone in your family has a history of heart attack or an irregular heartbeat (arrhythmia), especially a condition called “QT prolongation” or “long QT syndrome.”

Myasthenia Gravis. Tell your health care provider if you have a condition called myasthenia gravis (MG). Azithromycin can make your symptoms, like muscle weakness and breathing problems, worse. 

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Pregnancy. It is not known if or how azithromycin could affect pregnancy or harm a fetus. Tell your health care provider if you are or plan to become pregnant.

Breastfeeding. Azithromycin passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should use azithromycin while breastfeeding. Monitor your baby for diarrhea, vomiting, or rash if you are breastfeeding while taking azithromycin.

Interactions

Does azithromycin interact with foods or drinks (drug interactions)?

There are no known interactions between azithromycin and foods or drinks.

It is unknown if drinking alcohol will affect azithromycin.

Does azithromycin interact with other medicines?

Always tell your health care provider about any prescription or OTC medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using azithromycin.

  • Nelfinavir, which is a medicine used for HIV
  • Warfarin, which is a blood thinner
  • Digoxin, which is a medicine used for heart problems
  • Colchicine, which is a medicine commonly used for gout
  • Phenytoin (Dilantin, Phenytek, and others), which is a medicine to control seizures
  • An antacid that contains aluminum or magnesium

Azithromycin may alter the blood levels of some other medicines. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with azithromycin. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much azithromycin?

If you or someone else has used too much azithromycin, get medical help right away, call 911, or call a Poison Control center at 800-222-1222. 

What should I do if I miss a dose of azithromycin?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.

It is important to complete your prescribed course of azithromycin, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to azithromycin or other similar medicines.