Karen Berger, PharmD, is a community pharmacist and medical writer/reviewer.

Mary Choy, PharmD, is board-certified in geriatric pharmacotherapy and is an active leader in professional pharmacy associations.

Zithromax (azithromycin ) is a prescription medication used to treat various bacterial infections, such as bronchitis, sinusitis, skin infections, and more. It works by stopping the growth of bacteria. Zithromax is in a drug class known as macrolide antibiotics.

It is available in oral form as a tablet, commonly under the brand name of Zithromax Z-Pack (a five-day regimen) or Zithromax Tri-Pak (a three-day regimen). It also comes in an oral suspension and injection form. The active ingredient in Zithromax, azithromycin, is also available as an eye drop under the brand name Azasite. However, this article will focus on the oral versions of azithromycin.

Brand Name(s): Zithromax, Zithromax Tri-Pak, Zithromax Z-Pak

Controlled Substance: N/A

Dosage Form(s): Tablet, suspension

Zithromax treats certain bacterial infections, such as:

Zithromax does not treat viral infections, such as the common cold, flu, or COVID-19.

Read the information guide that comes with your Zithromax prescription, and discuss any questions or concerns with your healthcare provider or pharmacist.

Take Zithromax exactly as prescribed by your healthcare provider. Do not skip doses or discontinue the medicine, unless your healthcare provider tells you to do so. Taking the medication for the full-time prescribed ensures the bacteria do not come back and helps prevent antibiotic resistance.

Oral Zithromax is taken by mouth. It can be taken with or without food. If you have stomach problems while taking Zithromax, try taking it with food.

Zithromax oral suspension, for children, is available as 100 or 200 milligrams (mg) per 5 milliliters (mL). It should be measured with a medication measuring device. Do not measure Zithromax with kitchen utensils because they are not accurate for measuring medicine. Shake the suspension before measuring it. Discard any remaining suspension after 10 days or as specified on the prescription label.

Zithromax in a single-dose, 1-gram packet, is not for children. It is for adults with certain sexually transmitted infections. The entire contents of the packet should be mixed with 60 milliliters of water. Drink the entire mixture right away, then add another 60 milliliters of water, mix, and drink. This ensures the entire dosage is taken. The single dose packet is only to give doses of 1 gram (1000 milligrams).

When taking Zithromax, avoid grapefruit and grapefruit juice. Grapefruit can increase the levels of azithromycin in your body. This can cause a dangerous heart rhythm.

Store Zithromax at room temperature (between 68 F and 77 F), away from heat, direct light, and moisture. Do not store it in the bathroom. Keep it in its original labeled container and out of the reach of children and pets to prevent accidental ingestion.

Sometimes Zithromax is used off-label for indications not Food and Drug Administration (FDA)-approved.

Off-label uses of azithromycin can include:

An oral dose of Zithromax reaches the highest level in the body in about two hours. When taking Zithromax, you may begin to feel better within a few days, but do not stop taking the medicine. Taking it for the prescribed length of time ensures you recover fully and the bacteria do not come back.

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your healthcare provider. You may report side effects to the FDA at fda.gov/medwatch or 1-800-FDA-1088.

The most common side effects of Zithromax are:

Call your healthcare provider immediately if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

Call your healthcare provider immediately if you have:

Notify your healthcare provider if you experience symptoms of potential liver problems, such as:

Call your infant's pediatrician if they experience vomiting or irritability when feeding while taking Zithromax.

Azithromycin is typically only taken short term. However, people who take azithromycin for a more extended period may be at risk of additional side effects, such as:

Some of the severe side effects listed above can also persist for a while. Be alert to any serious symptoms and call your healthcare provider or get emergency medical help if needed.

Zithromax may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

Due to the possible effects of this medication, there may be changes to how it is used. Therefore, Zithromax may require modifications for the following users:

If you miss a dose of Zithromax, take it as soon as you can. If it is almost time for the next dose, skip the missed dose. Do not take two doses together.

Taking more azithromycin than prescribed can cause side effects such as nausea, vomiting, and diarrhea.

If you think you or someone else may have overdosed on Zithromax, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Zithromax, call 911 immediately.

It is very important that your doctor check the progress of you or your child at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

If you or your child's symptoms do not improve within a few days, or if they become worse, check with your doctor.

This medicine may cause serious allergic reactions, including anaphylaxis and angioedema, which can be life-threatening and require immediate medical attention. Call your doctor right away if you or your child have a rash, itching, hives, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth after you take this medicine.

Serious skin reactions, including Stevens-Johnson syndrome, acute generalized exanthematous pustulosis, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS) can occur with this medicine. Check with your doctor right away if you or your child have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, swollen glands, unusual bleeding or bruising or unusual tiredness or weakness while you are using this medicine.

Check with your doctor right away if you or your child have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, unusual tiredness or weakness, or yellow eyes or skin. These could be symptoms of a serious liver problem.

Call your child's doctor right away if your child feels irritable or vomits after feeding. These may be symptoms of a condition called infantile hypertrophic pyloric stenosis.

Azithromycin may cause diarrhea, and in some cases it can be severe. It may occur 2 months or more after you stop using this medicine. Do not take any medicine to treat diarrhea without first checking with your doctor. Diarrhea medicines may make the diarrhea worse or make it last longer. If you or your child have any questions about this or if mild diarrhea continues or gets worse, check with your doctor.

This medicine can cause changes in heart rhythms, including QT prolongation. It may change the way your heart beats and cause fainting or serious side effects in some patients. Contact your doctor right away if you or your child have any symptoms of heart rhythm problems, including fast, pounding, or irregular heartbeats.

This medicine may increase the risk of serious heart or blood vessel problems. Call your doctor right away if you have blurred vision, chest pain, confusion, lightheadedness, dizziness, fainting, fast or irregular heartbeat, trouble breathing, or unusual tiredness or weakness.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Zithromax is not appropriate for everyone. You should not take Zithromax if allergic to azithromycin, inactive ingredients in Zithromax, or macrolide antibiotics such as Ery-Tab (erythromycin) or Biaxin XL (clarithromycin). People who have had liver problems or jaundice from previous Zithromax use should not take Zithromax.

Some people may use Zithromax with caution if the healthcare provider determines it is safe. This includes people who are 65 years and older and people with certain health conditions, such as:

Zithromax should not be used to treat pneumonia in people 65 years and older or who have:

Before taking Zithromax, tell your healthcare provider about all of the medicines you take, including prescription and over-the-counter (OTC) medicines, and vitamins or supplements. Your healthcare provider can advise you on any possible drug interactions.

The following drugs have major interactions with azithromycin. Avoid using these medications together if possible:

Other drugs that interact with azithromycin include:

In addition to these medications, grapefruit and grapefruit juice should be avoided when taking Zithromax. Other drugs interact with azithromycin, too. This is not a complete list of drug interactions.

Zithromax is a macrolide antibiotic. Other macrolide antibiotics include:

There are many other classes of antibiotics that can be used for various bacterial infections. These include:

You should consult a healthcare provider if you suspect an infection. Your healthcare provider will prescribe the right antibiotic that will be effective against the bacteria causing the infection.

This is a list of drugs also prescribed for bacterial infections. It is NOT a list of drugs recommended to take with Zithromax. Your healthcare provider will prescribe or recommend treatment based on the type of bacteria and infection you have.

Zithromax is an antibiotic. It contains the active ingredient azithromycin. Zithromax treats certain bacterial infections, such as bronchitis, pneumonia, ear, sinus, and skin infections, and sexually transmitted infections. Zithromax works on bacterial infections only, which means it won't help viral infections like the flu, cold, or COVID-19.

Zithromax is a macrolide antibiotic. It works by killing bacteria and preventing their growth.

There are many drugs that can possibly interact with Zithromax. Some of these drugs include warfarin (a blood thinner), fluconazole, and antacids that contain aluminum or magnesium. If you take an antacid, separate the dose from Zithromax by at least two hours. Avoid consuming grapefruit or grapefruit juice while taking Zithromax. Talk to your healthcare provider about all of the medications you take before taking Zithromax, so they can be sure there are no drug interactions.

A single dose of Zithromax reaches its highest levels in about two hours. You may start to feel better several days after you start taking Zithromax. Although you may feel better, do not stop taking Zithromax. Finishing the full course of antibiotics your healthcare provider prescribes ensures the infection clears up completely.

The most common side effects of Zithromax are stomach issues such as nausea, vomiting, diarrhea, and stomach pain.

In rare cases, a serious reaction may occur. Contact your healthcare provider right away if you have fatigue, stomach pain, fever, dark urine, or yellowing of the skin or whites of the eyes, which can indicate a liver problem. Another rare but serious reaction is a severe allergic reaction.

Seek emergency medical help if you have:

You will stop taking Zithromax once you've finished your last dose. Do not stop taking it earlier, even if your symptoms have resolved.

Before taking Zithromax, discuss all existing health conditions and your medical history with your healthcare provider. Tell them about all your medications, including prescription and OTC drugs and vitamins or herbal supplements. Zithromax interacts with various drugs, so providing this information helps ensure that it will be prescribed safely. Do not consume grapefruit or grapefruit juice when taking azithromycin.

Antibiotics like Zithromax must be taken for the full length of time prescribed. If you stop taking it too soon, the infection could return, or you may become resistant to the medicine. This means that the next time you need it, it might not work as well.

Talk to your healthcare provider or pharmacist about nonmedicinal measures you can take to help your symptoms get better, in addition to taking an antibiotic. For example, taking cough drops, using a vaporizer, and getting plenty of fluids can help ease the symptoms of a throat infection, while Zithromax takes care of the bacteria. Zithromax can make you more likely to burn in the sun, so avoid sunlight and tanning beds while on it. If you are outside, wear protective clothing and sunscreen.  

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

Prescribers' Digital Reference. Azithromycin - drug summary.

DailyMed. Label: Zithromax- azithromycin tablet, film coated.

Wildfeuer A, Laufen H, Leitold M, Zimmermann T. Comparison of the pharmacokinetics of three-day and five-day regimens of azithromycin in plasma and urine. J Antimicrob Chemother. 1993;31(Suppl E):51-56. doi:10.1093/jac/31.suppl_e.51

Li H, Liu DH, Chen LL, et al. Meta-analysis of the adverse effects of long-term azithromycin use in patients with chronic lung diseases. Antimicrob Agents Chemother. 2014;58(1):511-517. doi:10.1128/AAC.02067-13

By Karen Berger, PharmD Karen Berger, PharmD, is a community pharmacist and medical writer/reviewer.

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