Zithromax (Azithromycin) - Oral

What Is Zithromax?

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.

Drug Facts

Generic Name: Azithromycin

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

Drug Availability: Prescription

Administration Route: Oral

Therapeutic Classification: Antibiotic

Available Generically: Yes

Controlled Substance: N/A

Active Ingredient: Azithromycin

Dosage Form(s): Tablet, suspension

What Is Zithromax Used For?

Zithromax treats certain bacterial infections, such as:

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

How to Take Zithromax

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.

Off-Label Use

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

Off-label uses of azithromycin can include:

  • Acute salmonellosis (food poisoning caused by the bacteria Salmonella)
  • Babesiosis (a parasitic infection)
  • Campylobacteriosis (bacterial diarrhea illness)
  • Cervicitis (irritation or infection of the cervix)
  • Early Lyme disease
  • Pertussis (whooping cough)
  • Prevention of certain heart infections during dental treatment
  • Prevention of chronic obstructive pulmonary disease (COPD) exacerbation
  • Severe shigellosis (a bacterial infection that causes severe diarrhea)
  • Typhoid fever (a bacterial disease that may be spread through contaminated food or water and causes a high fever and other symptoms) in combination with other medications

How Long Does Zithromax Take to Work?

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.

What Are the Side Effects of Zithromax?

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.

Common Side Effects

The most common side effects of Zithromax are:

  • Gastrointestinal issues, such as nausea and vomiting, diarrhea, indigestion, flatulence (gas), or stomach pain
  • Dizziness 
  • Skin rash and itching 
  • Headache 
  • Appetite loss
  • Vaginal infection
  • Hearing loss (with high doses)

Severe Side Effects

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:

  • Hypersensitivity reaction/anaphylaxis: Symptoms may include rash, hives, difficulty breathing, and swelling around the face, lips, tongue, and throat.
  • Angioedema: Swelling under the skin
  • Acute generalized exanthematous pustulosis: Characterized by a high fever, rash, and pus-filled bumps on the skin.
  • Drug reaction with eosinophilia and systemic symptoms (DRESS): A severe, life-threatening reaction with fever, extensive rash, and organ involvement.
  • Stevens-Johnson syndrome: A medical emergency with flu-like symptoms, red or purple rash, and blisters.
  • Toxic epidermal necrolysis: A life-threatening skin disorder with peeling and blistering of the skin.
  • Antibiotic-associated diarrhea, which can be severe or life-threatening
  • Long QT syndrome (heart rhythm disorder)
  • Worsening of myasthenia gravis: An autoimmune disease with symptoms of weak muscles and vision problems.
  • Liver problems and jaundice: Yellowing of the skin and whites of the eyes.
  • Inflammation of the pancreas 

Call your healthcare provider immediately if you have:

  • Severe stomach pain
  • Watery or bloody diarrhea (this can occur up to several months after you stop taking azithromycin)
  • Sudden dizziness or fainting
  • Fast or pounding heartbeat

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

  • Nausea or vomiting
  • Appetite loss
  • Stomach pain
  • Fatigue
  • Itching
  • Dark urine
  • Clay-colored stools
  • Yellowing of the skin or whites of the eyes

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

Long-Term Side Effects

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:

  • Liver problems: In rare cases, azithromycin can cause liver problems or liver failure. People who take azithromycin long-term will have regular blood work to check liver function.
  • Diarrhea: Like any antibiotic, azithromycin can cause diarrhea, which can be serious or life-threatening. Diarrhea can occur right away, or even months after stopping the antibiotic. Report diarrhea to your healthcare provider immediately. Get emergency medical attention for severe diarrhea, especially if it is watery or bloody.
  • Hearing loss: A review of studies concluded that when Zithromax is used long-term for chronic lung disease, hearing loss can occur.
  • Antibiotic resistance: This means that the germs that cause infection no longer respond to the antibiotic. 

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.

Report Side Effects

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).

Dosage: How Much Zithromax Should I Take?

Drug Content Provided and Reviewed by IBM Micromedex®

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.

  • For oral dosage form (extended-release suspension):
    • For treatment of pneumonia:
      • Adults—2 grams (g) once as a single dose.
      • Children weighing 34 kilograms (kg) or more—Dose is based on body weight and must be determined by your doctor. The dose is usually 2 grams once a day, taken as a single dose.
      • Children 6 months of age and older weighing less than 34 kg—Dose is based on body weight and must be determined by your doctor. The dose is usually 60 milligrams (mg) per kilogram (kg) of body weight once a day, taken as a single dose.
    • For treatment of sinusitis:
      • Adults—2 grams (g) once a day as a single dose.
      • Children—Use and dose must be determined by your doctor.
  • For oral dosage forms (suspension or tablets):
    • For treatment of infections:
      • Adults—500 to 2000 milligrams (mg) once a day, taken as a single dose. Depending on the type of infection, this may be followed with doses of 250 to 500 mg once a day for several days.
      • Children 6 months of age and older—Dose is based on body weight and must be determined by your doctor. The dose is usually 10 to 30 milligrams (mg) per kilogram (kg) of body weight once a day, taken as a single dose. Depending on the type of infection, this may be followed with doses of 5 to 10 mg per kg of body weight once a day for several days.
      • Children younger than 6 months of age—Use and dose must be determined by your doctor.
    • For treatment of pharyngitis or tonsillitis:
      • Adults—500 milligrams (mg) on Day 1 (the first day), taken as a single dose. Then, 250 mg on Day 2 through Day 5.
      • Children 2 years of age and older—Dose is based on body weight and must be determined by your doctor. The dose is usually 12 milligrams (mg) per kilogram (kg) of body weight once a day for 5 days.
      • Children younger than 2 years of age—Use and dose must be determined by your doctor.


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:

  • Children: Children can take azithromycin for various bacterial infections. Oral suspension is usually prescribed in this age group, as it is easier to take. Zithromax can be used in children 6 months and older. However, it cannot be used to treat a throat or tonsil infection in children under the age of 2. 
  • Pregnant or breastfeeding people: People who are pregnant, plan to become pregnant, or are breastfeeding should talk to their healthcare provider before taking Zithromax.
  • Older adults: The safety and efficacy of Zithromax are similar in younger and older adults. However, the prescribing information states that some older adults may have greater sensitivity to the drug. Older adults with no kidney or liver problems can take a regular dose of Zithromax; however, older adults are at higher risk of heart rhythm disorders and may need to be cautious. 
  • People with liver problems: People with a history of liver problems that occurred with azithromycin use should not take Zithromax. Healthcare providers may or may not prescribe Zithromax to people with liver problems unrelated to Zithromax. These people may be able to use Zithromax with caution.
  • People with kidney problems: People with a creatinine clearance of greater than 10 milliliters (mL) per minute can take Zithromax without dosage adjustment. Healthcare providers may or may not prescribe Zithromax to people with a creatinine clearance of less than 10 milliliters per minute.

Missed Dose

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.

Overdose: What Happens If I Take Too Much Zithromax?

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

What Happens If I Overdose on Zithromax?

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.


Drug Content Provided and Reviewed by IBM Micromedex®

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.

What Are Reasons I Shouldn’t Take Zithromax?

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:

  • Kidney or liver problems
  • QT prolongation (a heart rhythm disorder) or a history or family history of QT prolongation
  • Torsades de pointes (a type of irregular heart rhythm associated with QT prolongation)
  • Recent heart attack
  • Slow heart rate 
  • Ventricular arrhythmias
  • Congestive heart failure (CHF)
  • Electrolyte abnormalities
  • Recent antibiotic-associated colitis (severe diarrhea caused by antibiotics)
  • Myasthenia gravis

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

  • Cystic fibrosis
  • An infection in the blood
  • An infection after being in the hospital
  • A weakened immune system due to HIV/AIDS or cancer

What Other Medications Interact With Zithromax?

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:

  • Pacerone (amiodarone)
  • Colchrys, Gloperba, and Mitigare (colchicine)
  • Pimozide
  • Noxafil (posaconazole)
  • Quinidine 
  • Betapace, Betapace AF, Sorine, Sotylize (sotalol)
  • Thioridazine

Other drugs that interact with azithromycin include:

  • Antacids that contain aluminum or magnesium: Take antacids and azithromycin two hours apart.
  • Neoral, Gengraf, and Sandimmune (cyclosporine)
  • Lanoxin (digoxin)
  • Diflucan (fluconazole)
  • Viracept (nelfinavir)
  • Dilantin (phenytoin)  
  • Jantoven (warfarin)

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.

What Medications Are Similar?

Zithromax is a macrolide antibiotic. Other macrolide antibiotics include:

  • Biaxin XL (clarithromycin)
  • Dificid (fidaxomicin), which is only used to treat antibiotic-related diarrhea
  • Erythromycin

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.

Frequently Asked Questions

  • What is Zithromax used for?

    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.

  • How does Zithromax work?

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

  • What drugs should not be taken with Zithromax?

    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.

  • How long does it take for Zithromax to work?

    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.

  • What are the side effects of Zithromax?

    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:

    • Hives, difficulty breathing, or swelling around the face, lips, throat, or tongue
    • A severe skin reaction
    • Signs of liver problems
  • When can I stop taking Zithromax?

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

How Can I Stay Healthy While Taking Zithromax?

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.  

Medical Disclaimer

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.

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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.
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  5. 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

  6. 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.