Macrolides: Antibiotic List, Uses, Side Effects & Safety
Updated: 6 days ago
Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review
Quick Answer: What are macrolides?
Macrolides are a class of antibiotics that stop bacteria from growing and treat bacterial infections such as walking pneumonia, whooping cough, strep throat and H. pylori. Common examples are azithromycin, clarithromycin, erythromycin and fidaxomicin. Nausea and diarrhea are the usual mild side effects. Take them only when prescribed, and seek emergency care for breathing trouble. [1]
What the research says
Macrolides raise the chance of stomach side effects. A review of 183 randomized trials with 252,886 participants found macrolides caused more diarrhea than placebo (odds ratio 1.70) — about 72 extra cases per 1,000 people treated, plus 62 extra cases of belly pain and 47 of nausea per 1,000. (Hansen et al., Cochrane Database of Systematic Reviews, 2019) [2]
Azithromycin and clarithromycin are linked to dangerous heart rhythms. A meta-analysis of 80 studies covering 39,374,874 patients found roughly 1.5 times the risk of ventricular arrhythmia or sudden cardiac death with azithromycin (RR 1.53) and clarithromycin (RR 1.52), mainly during recent or current use. (Wu et al., Frontiers in Cardiovascular Medicine, 2023) [3]
Overall deaths did not increase. Across placebo-controlled trials, people taking macrolides did not die more often than those taking placebo (odds ratio 0.96), even though stomach side effects were more common. (Hansen et al., Cochrane Database of Systematic Reviews, 2019) [2]
Key takeaways
Macrolides treat bacterial infections only — they do not work on colds or flu. [1]
The four most commonly prescribed macrolides are azithromycin, clarithromycin, erythromycin and fidaxomicin. [1]
Upset stomach is the most common side effect; serious reactions are rare. [1]
Macrolides can lengthen the heart's QT interval, so tell your provider about any heart rhythm condition. [1]
Always finish the full course, even when you feel better. [1]
What are macrolides?
Macrolides are a group (class) of antibiotics that treat bacterial infections by preventing bacteria from growing. Like all antibiotics, they won't treat viral infections such as the common cold or flu. [1]
A healthcare provider prescribes a macrolide when it's the best medicine for your specific infection. Macrolides are also a useful alternative if you're allergic to other antibiotics, such as penicillin. [1]
Which antibiotics are macrolides?
Azithromycin, clarithromycin, erythromycin and fidaxomicin are the macrolides most commonly prescribed in the United States. [1]
Macrolide | What to know |
Azithromycin | One of the most commonly prescribed macrolides |
Clarithromycin | Combined with another antibiotic and a proton pump inhibitor to treat ulcers caused by H. pylori |
Erythromycin | Also available as a skin gel used to help control acne |
Fidaxomicin | Used to treat C. diff infection |
Clindamycin is not a macrolide. It belongs to a different class called lincosamides, although it stops bacterial growth in a similar way. [1]
What infections do macrolides treat?
Macrolides treat a wide range of bacterial infections affecting the lungs, gut, throat, skin, eyes and urinary or genital tract. [1]
Body area | Infections |
Lungs and airways | Atypical ("walking") pneumonia, whooping cough, Legionnaires' disease, diphtheria, nontuberculous mycobacteria (NTM) infections |
Gut | C. diff infection, H. pylori infection, Campylobacter infection, severe traveler's diarrhea |
Throat, skin and eyes | Strep throat (usually in people with a penicillin allergy), bacterial eye infections, cat scratch fever |
Sexual and urinary | Chlamydia and other sexually transmitted infections, urethritis |
Erythromycin gel treats acne because bacteria on the skin can clog pores and contribute to breakouts. Applying the gel helps control those surface bacteria. [1]
Providers sometimes pair a macrolide with other medicines. For peptic ulcers caused by H. pylori, clarithromycin is combined with another antibiotic and a proton pump inhibitor. [1]
How do you take a macrolide?
Macrolides are taken in the form your provider prescribes, which can be a pill, a liquid, a skin gel or solution, an eye ointment or an injection. [1]
Form | How it's used |
Pills | Swallowed |
Liquids | Swallowed, measured with the device that comes with the medicine |
Gels or solutions | Applied to the skin |
Ointments | Applied along the inner eyelid |
Injections | Given by a healthcare provider |
Follow the directions on the prescription label and ask your provider if anything is unclear. For liquids, always use the measuring device supplied with the medicine — a household spoon isn't an accurate way to measure a dose. [1]
How long does a course of macrolides last?
The length of a macrolide course depends on the type of infection and your overall health, and your provider will tell you the exact number of days. [1]
Take the medicine for exactly as long as prescribed. If you stop too soon — even when you feel better — the antibiotic may not clear all the bacteria, and the infection can come back stronger. [1]
What are the benefits of macrolides?
Macrolides successfully treat many different bacterial infections and are safe and effective for most people. [1]
They also give providers an option for certain conditions when you're allergic to other antibiotics, such as penicillin. [1]
What side effects can macrolides cause?
An upset stomach is the most common side effect of macrolides, and it's usually mild. [1]
Side effect | How common | What to do |
Nausea, vomiting, belly pain or cramping, diarrhea | Common, usually mild | Tell your provider if it stops you taking the medicine |
Rash or other allergic reaction | Rare | Call your provider |
Stevens-Johnson syndrome or toxic epidermal necrolysis | Rare, serious | Get urgent medical care |
Abnormal heart rhythm | Not common | Tell your provider about heart conditions before starting |
The chance of stomach upset varies by macrolide — some are more likely to cause it than others — and your provider will tell you what to expect. [1]
Allergic reactions are rare, and a rash is the most common sign. [1][4] Serious skin reactions are rare but include Stevens-Johnson syndrome and its most severe form, toxic epidermal necrolysis. [1]
Do macrolides interact with other medicines or alcohol?
Macrolides can interact with other medicines, which may stop some of your medicines from working as well as they should. [1]
Tell your provider about every medicine and supplement you take. Also tell them whether and how often you drink alcohol — you may need to avoid it, because alcohol can interact with medicines and make antibiotics less effective. [1]
Can macrolides cause heart rhythm problems?
Macrolides can, uncommonly, cause abnormal heart rhythms (arrhythmias) because they may prolong the heart's QT interval. [1]
The QT interval is the time the heart muscle takes to contract and then recover. When it's longer than normal, you're at risk of a dangerous arrhythmia called torsades de pointes. [1]
If you have long QT syndrome or another condition that raises your arrhythmia risk, your provider may choose a different antibiotic. [1]
How long does it take to feel better on a macrolide?
Recovery time on a macrolide depends on the type of infection you have, and your provider will tell you what to expect. [1]
Feeling better before the course ends doesn't mean the infection is gone. Finishing every dose is what clears it. [1]
When should you call a doctor about macrolides?
You should call your provider if you have questions about your medicine, side effects that make it hard to keep taking it, a rash or other allergy signs, or symptoms that remain after you finish the course. [1]
Call your provider | Go to the emergency room |
Questions about how to take your medicine | Watery diarrhea several times in one day |
Side effects (like nausea or vomiting) that make it hard to take your medicine | Signs of dehydration |
Symptoms that continue after finishing the course | Trouble breathing or other signs of anaphylaxis |
A rash or other signs of an allergic reaction |
Anaphylaxis is a severe allergic reaction that needs immediate medical attention. [1]
Conclusion
Macrolides are a well-established antibiotic class that treats many bacterial infections, from walking pneumonia and whooping cough to H. pylori and chlamydia. Most people tolerate them well, with a mild upset stomach being the main complaint. Take them only when prescribed, finish the full course, share your medicine list and heart history with your provider, and act fast on severe diarrhea or breathing trouble.
Want to understand the infection you're being treated for? Read our guides to pneumonia, H. pylori and antibiotic-associated diarrhea, or explore our clinical overview of macrolide pharmacology and the plain-language azithromycin drug information to prepare questions for your next appointment.
FAQ
Is clindamycin a macrolide?
Clindamycin is not a macrolide; it belongs to the lincosamide class of antibiotics. Clindamycin and macrolides do stop bacterial growth in similar ways. [1]
Do macrolides treat colds or flu?
Macrolides do not treat colds or flu, because those are viral infections. Macrolides only work against bacteria. [1]
Can I take a macrolide if I'm allergic to penicillin?
Macrolides are often an alternative for people allergic to penicillin. For strep throat, for example, they're typically used in people with a penicillin allergy. [1]
Can I drink alcohol while taking a macrolide?
Alcohol may need to be avoided while taking a macrolide, because it can interact with medicines and make antibiotics less effective. Tell your provider whether and how often you drink. [1]
Should I stop a macrolide when I feel better?
A macrolide course should be finished exactly as prescribed, even if you feel better. Stopping early can leave bacteria behind and let the infection come back stronger. [1]
What are the most common side effects of macrolides?
The most common side effects of macrolides are nausea, vomiting, belly pain or cramping, and diarrhea. These are usually mild. [1]
When is diarrhea on a macrolide an emergency?
Diarrhea on a macrolide is an emergency when it's watery and happens several times in one day, or when you show signs of dehydration. Go to the emergency room in either case. [1]
Are macrolides safe if I have long QT syndrome?
Macrolides may not be the right choice if you have long QT syndrome, because they can prolong the QT interval and trigger a dangerous arrhythmia. Your provider may recommend a different antibiotic. [1]
Which antibiotics are macrolides?
The most commonly prescribed macrolides are azithromycin, clarithromycin, erythromycin and fidaxomicin. Your provider chooses one based on the type of infection.
Do macrolides interact with other medicines?
Yes. Macrolides can interact with some other medicines and change how well they work. Tell your provider and pharmacist about every medicine and supplement you take.
Related Reading
Tetracyclines: Uses, Side Effects and Safety explains tetracycline antibiotics such as doxycycline.
Antibiotics: Types, Uses, Side Effects and Resistance explains how antibiotics work and how to use them safely.
References
Cleveland Clinic. Macrolide Antibiotic: Examples, Uses & Side Effects. Cleveland Clinic. Last updated February 19, 2025. https://my.clevelandclinic.org/health/treatments/macrolides
Hansen MP, Scott AM, McCullough A, et al. Adverse events in people taking macrolide antibiotics versus placebo for any indication. Cochrane Database of Systematic Reviews. 2019;1(1):CD011825. PMID 30656650. https://doi.org/10.1002/14651858.CD011825.pub2
Wu Y, Bi WT, Qu LP, et al. Administration of macrolide antibiotics increases cardiovascular risk. Frontiers in Cardiovascular Medicine. 2023;10:1117254. PMID 36910529. https://doi.org/10.3389/fcvm.2023.1117254
Shaeer KM, Chahine EB, Varghese Gupta S, et al. Macrolide Allergic Reactions. Pharmacy (Basel). 2019;7(3):135. PMID 31540456. https://doi.org/10.3390/pharmacy7030135
Disclaimer
This article is for general educational purposes and does not replace advice from a qualified healthcare professional. Take antibiotics only as prescribed, and contact your provider or emergency services if you have concerning symptoms.
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