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What is azithromycin?

Azithromycin is a type of antibiotic medication classified as a macrolide.¹

It works by binding to a key part of the bacteria’s genetic material, preventing it from making important proteins.

Your doctor may prescribe azithromycin to treat mild to moderate infections caused by certain susceptible bacteria.

What is azithromycin used to treat?

Azithromycin is classified as a broad-spectrum antibiotic, meaning it can effectively treat a wide range of bacterial infections.²

Your doctor may determine that azithromycin is the best antibiotic to treat your illness if you’re diagnosed with one of the following conditions:³

  • Chronic bronchitis caused by Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae

  • Bacterial sinusitis caused by Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae

  • Community-acquired pneumonia caused by Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, or Streptococcus pneumoniae

  • Pharyngitis/tonsillitis caused by Streptococcus pyogenes — azithromycin may be prescribed if you cannot use first-line therapy

  • Uncomplicated infections of the skin and skin structure caused by Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae

  • Urethritis and cervicitis caused by Chlamydia trachomatis or Neisseria gonorrhoeae

  • Genital ulcer disease in men caused by Haemophilus ducreyi (chancroid)

In children, azithromycin is approved for treating the following indications:

  • Ear infections (otitis media) in children aged six months and over that are caused by Moraxella catarrhalis, Haemophilus influenzae, or Streptococcus pneumoniae

  • Community-acquired pneumonia in children aged six months and over that has been caused by Chlamydophila pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, or Streptococcus pneumoniae

  • Pharyngitis/tonsillitis in children aged two years and over that has been caused by Streptococcus pyogenes

Azithromycin 600mg oral tablets are approved for the treatment and prevention of disseminated Mycobacterium avium complex disease in people with advanced HIV infection.⁴

Azithromycin for intravenous use is only given to treat community-acquired pneumonia in adults and pelvic inflammatory disease.⁵

AzaSite ophthalmic drops are approved to treat bacterial conjunctivitis caused by Corynebacterium CDC group G, Haemophilus influenzae, Staphylococcus aureus, Streptococcus mitis group, or Streptococcus pneumoniae.⁶

Dosage forms and strengths

Azithromycin is a generic medication that is also available as brand-name products.

The following are the available dosage forms and strengths:

  • Tablet for oral use:

    • 250mg and 500mg (also available under the brand name Zithromax)³ ⁷

    • 600mg⁴

  • Packet: 1g per packet⁸

  • Powder for suspension, for oral use: 100mg/5mL and 200mg/5mL (also available under the brand name Zithromax)⁹

  • Solution for intravenous use: 500mg and 2.5g¹⁰

  • Solution for ophthalmic use (AzaSite): 1%⁶

How do you take azithromycin?

You should take azithromycin exactly as your doctor prescribes. It is critical to take the full course of your antibiotic, even if you’re feeling better, to reduce the risk of developing an antibiotic-resistant infection.

Do not take this medication in larger or smaller amounts than recommended.

You can take most forms of oral azithromycin with or without food.

For instructions on how to take the oral suspension, follow the usage instructions given on the bottle.

Seeing results

Azithromycin typically begins working rather quickly, but it can take a few hours to reach peak concentrations in your body.

Many people find their symptoms start to resolve within a few days of beginning treatment. However, everyone is different. How fast the antibiotic works for you depends on several factors, including the cause, type, and severity of your infection.

For example, a single oral dose of azithromycin might clear genital chlamydia within a week or so, but it could take longer for the symptoms of pneumonia to resolve, even with consistent dosing over multiple days.

Although treatment with azithromycin is typically shorter in duration compared to other types of antibiotics, current investigations suggest the drug could remain in your system for more than two weeks after taking your final dose.¹¹

Who should not take azithromycin?

Although azithromycin is considered safe and effective for most people, it’s not suitable for everyone. The antibiotic can cause potentially serious complications for those diagnosed with the following conditions:¹²

  • Previous history of allergic reaction to azithromycin (or an antibiotic from the same class)

  • Liver or kidney disease

  • Cardiovascular disease or an irregular heartbeat (arrhythmia)

  • Myasthenia gravis

Azithromycin is also known to interact with several medications, including other antibiotics, antipsychotics, antacids, and more (please see the section on drug interactions below). If you have a medical condition or take medication, your prescriber will need a complete understanding of your medical history and the medications you take.

Warnings and precautions

The US Food and Drug Administration (FDA) released public statements cautioning patients and their physicians that azithromycin can cause abnormal electrical activity of the heart, including potentially fatal heart rhythm irregularities. You may be at risk of these effects if you have been diagnosed with prolonged QT interval or a slow heart rate, or if you have low levels of potassium or magnesium in your blood. Taking certain drugs that are used to treat arrhythmias could also increase your risk.¹³

Azithromycin drug labels also carry warnings for the following adverse effects:³

  • Potentially fatal allergic reactions, including angioedema, anaphylaxis, and dermatologic reactions

  • Toxic liver disease (hepatotoxicity)

  • Infantile hypertrophic pyloric stenosis (IHPS)

  • Cardiovascular death

  • Clostridioides difficile-associated diarrhea (CDAD)

  • Exacerbated muscle weakness in people with myasthenia gravis

Potential side effects of azithromycin

Like any medication, azithromycin can cause side effects. Most are generally mild and resolve on their own. Ask your clinician for advice if you experience any of the following: 

  • Headache

  • Nausea or vomiting

  • Loose stools or diarrhea

  • Loss of appetite

  • Abdominal discomfort

  • Rash, itching, or dizziness

Severe side effects

While less common, some people taking azithromycin develop adverse effects that require immediate medical attention, including potentially serious heart rhythm disorders and liver dysfunction.¹⁴

Contact your prescriber or seek immediate care if you develop any of the following symptoms during (or after) azithromycin treatment:³

  • Chest pain or palpitations

  • Sudden dizziness or fainting

  • Muscle weakness

  • Visual disturbances

  • Tinnitus (ringing in the ears)

  • Yellowing skin

  • Clay-colored stools or dark urine

  • Skin rash, hives, or itching

  • Severe diarrhea with fever

  • Severe abdominal pain, back pain, or blood in your stool

Rare side effects

In rare cases, some people taking azithromycin can develop the following complications:

  • Prolonged QT interval (heart rhythm disorder)

  • Rapid ventricular heartbeat or slow heart rate (bradycardia)¹⁵

  • Liver damage¹⁶

  • Hearing loss¹⁷

  • Decreased blood platelet counts¹⁸

When to seek medical attention for side effects

When taken according to directions, azithromycin is safe and effective. However, you should inform your prescriber of any adverse effects you experience, especially any symptoms that are particularly bothersome or persistent.


It is possible to overdose on azithromycin. Contact the Poison Control helpline and seek emergency medical attention. Your symptoms could include (but are not limited to) the following:³ ¹⁹

  • Vomiting

  • Diarrhea

  • Palpitations or chest pain

  • Fainting or loss of consciousness

  • Seizures

  • Hearing loss (reversible)

  • Severe abdominal pain

Allergic reactions

Severe allergic reactions to azithromycin are uncommon but can occur. Call 911 or visit your nearest emergency department if you experience the following signs of a severe allergic reaction:²⁰

  • Hives or itching

  • Swelling of the throat or tongue

  • Difficulty breathing

  • Facial swelling

  • A red or purple rash

  • Blistered or peeling skin

Long-term use of azithromycin

Azithromycin is usually prescribed as a short course of treatment for most infections. However, your prescriber might suggest long-term therapy for conditions like severe chronic obstructive pulmonary disease or cystic fibrosis.²¹ ²²

If your doctor prescribes low-dose azithromycin for long-term use, they may recommend an ECG, complete blood count, and liver function tests to establish a baseline before your treatment begins. This way, they can monitor the impact of taking azithromycin over time to ensure the benefits continue to outweigh any risk to your health.²³

Pregnancy category

Azithromycin is designated as a pregnancy category B drug, a determination made by the FDA. This means animal studies have not revealed evidence of risk when the drug is given during pregnancy, but no sufficient studies have been carried out in human pregnancy.²⁴ ²⁵

Azithromycin and pregnancy

While there are no adequate studies detailing human risk, animal studies have not demonstrated an increased risk of congenital malformations. This means that the risk to the human fetus is unknown at this time.

Tell your doctor if you are pregnant before taking azithromycin. If you discover you are pregnant during treatment, inform your doctor as soon as possible.

Azithromycin and breastfeeding

Azithromycin is detectable in human milk. In fact, research has demonstrated the presence of azithromycin in breast milk for up to four weeks.

Non-serious adverse effects have been reported in breastfed infants whose mothers have taken the drug (up to 48 hours). It is therefore recommended that breastfed infants be closely monitored for vomiting, diarrhea, and rash.³

Missed doses

Ideally, you should take azithromycin at the same time each day. If you forget a dose, take it as soon as you can. However, if it’s nearly time for your next dose, do not double your medication. Instead, skip that pill (or liquid dose) and take your next dose as scheduled. Then continue your treatment until you have taken every dose prescribed. If you have questions or concerns, consult your prescriber or local pharmacist.

Drug interactions

Azithromycin can interact with several medications. Inform your doctor of any prescription or over-the-counter medications you’re currently taking or begin taking, including any herbs or supplements. Just a few of the many medications and supplements the antibiotic could interact with include the following:²⁶

  • Albuterol sulfate (Accuneb, Proair Respiclick)

  • Antacids made with aluminum or magnesium

  • Black cohosh

  • Cannabidiol (CBD)

  • Colchicine (Colcrys, Gloperba)

  • Digoxin (Cardoxin, Digitek, Lanoxicaps, Lanoxin) and other heart medications

  • Fluticasone propionate-salmeterol (Advair)

  • Nelfinavir (Viracept)

  • Phenytoin (Dilantin, Phenytek) and other seizure medications

  • Statins

  • Warfarin (Coumadin, Jantoven)

Can you drink alcohol while taking azithromycin?

There is no known contraindication for drinking alcohol while taking azithromycin and no warning on the package insert to suggest the need to avoid alcohol. However, the combination could make any side effects, like headaches, nausea, or digestive distress, feel worse.²⁷

It is important to keep in mind that alcohol can irritate your stomach, interrupt your sleep, and cause dehydration, making it more difficult for your body to fight the infection being treated by azithromycin.

What should you tell your doctor before starting this medication?

Doctors typically prescribe antibiotics to treat bacterial infections. But not all antibiotics are the same. It’s a good idea to discuss the following topics with your doctor before taking azithromycin, including:

  • Previous allergic reactions to similar medications (including erythromycin or clarithromycin)

  • Your current use of all prescription and over-the-counter medications, whether daily or occasional

  • Any vitamins, herbs, or supplements you take

  • Whether you are pregnant, breastfeeding, or planning a pregnancy within the next few months

  • Your health history, including any heart rate irregularities or low potassium levels

  • Any previous history of liver disease, kidney disease, or myasthenia gravis

  • Any family history of long QT syndrome or other heart rhythm disturbances

  • Any questions or concerns you may have about taking this medication

How to stop taking azithromycin

You should continue taking azithromycin as directed by your prescriber. Do not stop taking the antibiotic unless instructed to do so, even if you’re feeling better. Stopping mid-treatment increases the risk of developing a recurrence of your infection or an antibiotic-resistant infection.

Drug approval history

Azithromycin was initially discovered by the Croatian pharmaceutical company Pliva during the late 1970s. During their initial trials, the antibiotic proved itself efficacious and capable of remaining in the body longer than other antibiotics. But it took years for the company to benefit from that discovery.²⁸

In 1981, Pliva filed a patent in the country once known as Yugoslavia, then worldwide. Those initial patents proved to be the key to the antibiotic’s success. Pfizer scientists searching the US Patent and Trade Office recognized its enormous potential. By 1986, Pliva and Pfizer reached a mutually beneficial licensing agreement. Azithromycin achieved FDA approval in 1991 to be sold under the brand name Zithromax.²⁹

Tips for taking azithromycin

Most people start feeling better within a few days of beginning treatment. If your symptoms do not improve after taking azithromycin for 3–5 days or if you start feeling worse at any time, contact your doctor.

Use the following tips to help ensure favorable results:

  • Take your medication exactly as instructed.

  • Set a timer to reduce the risk of forgetting a dose.

  • Avoid driving or operating heavy equipment if the medication makes you feel dizzy.

  • Ask your doctor or pharmacist before starting any new medications or using over-the-counter medications or supplements.

  • Azithromycin tablets can be taken with or without food.

  • Azithromycin extended-release suspension should be taken one hour before or two hours after eating.

  • Contact your prescriber if you experience troubling side effects.

  • Side effects causing severe (24-hour) vomiting or diarrhea can interfere with some oral contraceptives.

  • Keep your medication out of reach of children and away from pets.

Frequently asked questions

When is azithromycin best taken?

Follow your doctor’s or pharmacist’s instructions carefully when taking this medication. You can take most forms of oral azithromycin with or without food.

Is azithromycin used to treat coughs and colds?

Azithromycin is an antibiotic, so it is ineffective against viruses such as those that cause the flu or common cold. The drug may be prescribed when a bacterial infection is thought to be the cause of a cough or other respiratory tract infections.

What should I avoid when taking azithromycin?

Azithromycin interacts with some drugs, including CBD, colchicine, digoxin, and warfarin. This may cause harmful effects. Ensure your doctor knows which other medications, herbal remedies, and supplements you are taking to prevent potential interactions.

  1. Azithromycin (1992)

  2. Prescribing azithromycin (2015)

  3. Label: Azithromycin tablet, film coated | NIH: DailyMed

  4. Label: Azithromycin- azithromycin tablet, film coated | NIH: DailyMed

  5. Label: Azithromycin- azithromycin dihydrate injection, powder, iyophilized, for solution | NIH: DailyMed

  6. Label: Azasite- azithromycin monohydrate solution/ drops | NIH: DailyMed

  7. Label: Zithromax- azithromycin dihydrate tablet, film coated ; Zithromax- azithromycin dihydrate powder, for suspension | NIH: DailyMed

  8. Label: Azithromycin tablet, film coated ; Azithromycin powder, for suspension | NIH: DailyMed

  9. Label: Azithromycin powder, for suspension | NIH: DailyMed

  10. Label: Azithromycin- azithromycin dihydrate injection, powder, lyophilized, for solution | NIH: DailyMed

  11. Pharmacokinetic considerations regarding the treatment of bacterial sexually transmitted infections with azithromycin: a review (2019)

  12. Azithromycin dihydrate tablet | NIH: DailyMed

  13. FDA drug safety communication: Azithromycin (Zithromax or Zmax) and the risk of potentially fatal heart rhythms | U.S. Food & Drug Administration

  14. Azithromycin (2022)

  15. Azithromycin-induced bradycardia | Cureus

  16. Clinical and histological features of azithromycin-induced liver injury (2016)

  17. Prescribing azithromycin (2015)

  18. Azithromycin-induced thrombocytopenia: A rare etiology of drug-induced immune thrombocytopenia (2019)

  19. Get poison control help | Poison Control Helpline

  20. Macrolide allergic reactions (2019)

  21. Long-term azithromycin therapy to reduce acute exacerbations in patients with severe chronic obstructive pulmonary disease (2018)

  22. Long term azithromycin therapy in patients with cystic fibrosis (2016)

  23. Long term azithromycin (adults) – prescribing and monitoring responsibilities (2019)

  24. Use of azithromycin in pregnancy: More doubts than certainties (2022)

  25. Pregnancy medications (2022)

  26. Taking azithromycin with other medicines and herbal supplements | NHS

  27. Fact versus fiction: a review of the evidence behind alcohol and antibiotic interactions (2020)

  28. Azithromycin: A world best-selling Antibiotic | World Intellectual Property Organization (WIPO)

  29. Drugs@FDA: FDA-approved drugs | U.S. Food & Drug Administration

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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.