Quick answer: Azithromycin (Zithromax, “Z-Pak”) interacts with fewer drugs than older macrolide antibiotics like erythromycin and clarithromycin, but it is not interaction-free. The most important concern is heart rhythm: azithromycin can prolong the QT interval, so combining it with other QT-prolonging medicines (certain antiarrhythmics, antipsychotics, some antidepressants, methadone, other antibiotics and more) deserves a pharmacist’s review. Other pairings to check include warfarin, digoxin, colchicine, cyclosporine and tacrolimus, ergot medicines, and aluminum or magnesium antacids, which should be spaced apart from the dose. Food, dairy and most supplements are minor issues, though a few details are worth knowing.
How to use this guide
Most interaction articles are long lists that leave you guessing which items matter. This one is organized by how much each interaction should concern you. We sort them into three tiers, explain the reasoning behind each, then give you a step-by-step way to check your own medicine list and a script for talking to your pharmacist. Medicines mentioned here are examples, not complete lists, so always run your full list past a professional.
Azithromycin is a macrolide antibiotic prescribed for certain respiratory infections, ear infections, skin infections, some sexually transmitted infections and other bacterial illnesses. If you are comparing it with another common antibiotic, see amoxicillin vs azithromycin. For the other antibiotic’s interaction profile, see amoxicillin drug interactions.
Why azithromycin interacts less than other macrolides
Many drug interactions happen in the liver, where enzymes such as CYP3A4 break medicines down. Erythromycin and clarithromycin strongly block CYP3A4, which can cause other drugs to build up to dangerous levels. Azithromycin has a different chemical structure and is a much weaker inhibitor of these enzymes. That is why it is often chosen when a patient takes many medicines.
But “fewer” does not mean “none.” Azithromycin can affect drug transporters such as P-glycoprotein, it can alter heart rhythm directly, and it can interact physically with certain products in the gut. Those are the mechanisms behind the interactions below.
The three-tier map
| Tier | What it means | Examples in this guide |
|---|---|---|
| Tier 1: Needs professional review before combining | Potentially serious outcomes. Often avoided, or used only with monitoring | QT-prolonging drugs, warfarin, ergot derivatives |
| Tier 2: Use caution, monitoring or timing changes | Interaction is plausible or documented, and usually manageable | Digoxin, colchicine, cyclosporine, tacrolimus, some statins, aluminum or magnesium antacids |
| Tier 3: Usually minor or no meaningful interaction | Worth knowing so you do not worry or change habits unnecessarily | Most foods, grapefruit, most vitamins, birth control pills |
Tier 1: needs review before combining
1. Medicines that also prolong the QT interval
The QT interval is the part of the heartbeat tracing that reflects how long the heart muscle takes to reset between beats. When it stretches too far, a dangerous rhythm called torsades de pointes can occur. In March 2013 the FDA issued a drug safety communication warning that azithromycin can cause abnormal electrical activity of the heart, and it updated labeling accordingly. You can read the agency’s summary by searching the FDA drug safety communications for azithromycin. A 2012 study in the New England Journal of Medicine found a small increase in cardiovascular deaths during a five-day azithromycin course compared with amoxicillin, concentrated among people who already had high cardiovascular risk. Later studies produced mixed results, so the true size of the risk is debated. The consensus is that for most healthy people the absolute risk is very low, while for people with heart disease or other risk factors it deserves attention.
Adding a second QT-prolonging drug can stack the effect. Categories that regularly appear on QT lists include:
| Category | Examples |
|---|---|
| Antiarrhythmics | Amiodarone, sotalol, dofetilide, quinidine, procainamide |
| Antipsychotics | Haloperidol, ziprasidone, quetiapine, chlorpromazine, pimozide |
| Antidepressants | Citalopram, escitalopram (dose-related), some tricyclics. See Celexa vs Lexapro |
| Other antibiotics and anti-infectives | Fluoroquinolones (levofloxacin, moxifloxacin), clarithromycin, erythromycin, some antifungals such as fluconazole, chloroquine and hydroxychloroquine |
| Opioid treatment | Methadone. See methadone vs Subutex |
| Anti-nausea drugs | Ondansetron, domperidone (where available) |
| Antihistamines | Hydroxyzine. See Ativan vs hydroxyzine |
| Cancer and other specialty drugs | Several kinase inhibitors, arsenic trioxide and others |
A free-to-search reference for QT risk is CredibleMeds, which classifies drugs by the strength of evidence for QT effects. Pharmacists often check this when a patient has a risky combination.
Who is more vulnerable to QT problems?
- People with a known long QT syndrome or a family history of sudden unexplained death at a young age
- Slow heart rate (bradycardia), heart failure, a recent heart attack or other structural heart disease
- Low blood potassium or magnesium, which can result from vomiting, diarrhea, some diuretics, heavy sweating or poor intake
- Older adults, and women, who on average have slightly longer QT intervals
- Anyone taking two or more QT-prolonging drugs, or taking a drug that raises the level of another
Warning signs to act on include fainting, a pounding or irregular heartbeat, new dizziness or seizures while on the medicine. Call emergency services for fainting or a racing heartbeat with chest discomfort or shortness of breath.
2. Warfarin and other blood thinners
There have been post-marketing reports of increased anticoagulant effect when azithromycin is given with warfarin, and the labeling advises monitoring prothrombin time. Infection itself, poor appetite and changes in gut bacteria can also shift INR values, which makes it hard to attribute any change to the antibiotic alone. If you take warfarin, tell the clinic managing your INR that you are starting an antibiotic, and ask whether an earlier blood test is needed. Newer anticoagulants such as apixaban and rivaroxaban have different interaction profiles, so ask your pharmacist about whichever you take. For a broader look at drugs and clotting, see does oxycodone thin your blood.
3. Ergot derivatives
Ergotamine and dihydroergotamine, used for migraine, can cause severe narrowing of blood vessels (ergotism). Interactions with macrolides, particularly the stronger enzyme inhibitors, led to warnings, and azithromycin labeling advises against combining with ergot derivatives because of that theoretical risk. If you use these migraine products, say so before starting any macrolide.
Tier 2: use caution, monitoring or timing changes
4. Digoxin
Azithromycin may raise digoxin levels, probably by affecting the transporter P-glycoprotein, and cases of digoxin toxicity have been reported. Signs of too much digoxin include nausea, vomiting, vision changes such as yellow-green halos, confusion and a slow or irregular heartbeat. If you take digoxin, your prescriber may check a blood level or watch for symptoms during the antibiotic course.
5. Colchicine
Colchicine, used for gout and familial Mediterranean fever, is a P-glycoprotein substrate. Macrolide antibiotics have been linked to colchicine toxicity, mainly the stronger inhibitors, with some reports for azithromycin as well. The danger is higher in people with kidney or liver impairment. Ask your prescriber whether a dose change or alternate antibiotic is sensible.
6. Cyclosporine, tacrolimus and other transplant drugs
Immunosuppressants have narrow safe ranges. Azithromycin has less effect on their levels than clarithromycin, but labeling and clinical practice advise monitoring of blood levels when combined. Transplant patients should not start an antibiotic without their transplant team knowing.
7. Statins
Statins such as simvastatin and lovastatin rely on CYP3A4, and the strong macrolide inhibitors can raise their levels and the risk of muscle injury (rhabdomyolysis). Azithromycin is much less likely to do this, but isolated case reports exist, so prescribers sometimes pause a statin or advise watching for unexplained muscle pain, weakness or dark urine. Report those symptoms promptly.
8. Aluminum- and magnesium-containing antacids
This is the one interaction most people can manage with timing alone. Studies found that aluminum and magnesium antacids reduce peak blood levels of azithromycin, although total absorption was not changed much. The prescribing information advises not taking them at the same time. A common practical approach is to separate doses by at least two hours, taking azithromycin first. Check the label for your specific product on DailyMed and ask your pharmacist about timing if you rely on antacids.
Because other products also contain these minerals, apply the same caution to magnesium supplements and to laxatives or “milk of magnesia,” as a general precaution. Studies on those specific items are limited, so the advice is to space them out rather than to assume they are harmless.
9. Nelfinavir and certain HIV medicines
Nelfinavir can raise azithromycin levels. The labeling suggests monitoring for side effects such as liver or hearing effects, rather than avoiding the combination. People living with HIV should have antibiotic choices reviewed against their regimen.
10. Other drugs that depend on P-glycoprotein or cause liver stress
The list of sensitive drugs is long, and new ones are added as evidence accumulates. Rather than memorizing it, treat any medicine with a narrow safety margin (a drug where a small change in level matters) as a reason to ask. For similar-style reference guides on other drugs people often take together, see our articles on Luvox drug interactions, Prozac drug interactions, Dexedrine drug interactions and Adderall drug interactions. Many of those drugs affect heart rhythm, blood pressure or serotonin, so they deserve a pharmacist’s review alongside azithromycin.
Tier 3: foods, drinks and everyday items
Food and meals
Azithromycin tablets and standard liquid forms can generally be taken with or without food, according to the usual labeling. Taking a dose with a light meal can ease nausea or stomach upset for some people. Extended-release forms have different instructions, so follow the label on your product. For how food affects other antibiotics, our article on how long amoxicillin takes to work discusses timing, and the side-effect page amoxicillin and diarrhea is relevant because azithromycin shares that gut effect.
Dairy and calcium
Unlike tetracyclines and fluoroquinolones, azithromycin is not known to bind strongly to calcium in milk or yogurt. You do not usually need to avoid dairy. If you take calcium-based antacids or supplements, a few hours of separation is a reasonable, low-cost precaution.
Grapefruit
Grapefruit juice affects CYP3A4, but azithromycin is not mainly cleared by that enzyme, and grapefruit is not generally listed as a significant problem for it. If you take other medicines that do interact with grapefruit, such as certain statins, keep avoiding it.
Alcohol
There is no well-established direct chemical interaction between azithromycin and alcohol. But alcohol can worsen nausea, dizziness and dehydration, and may make it harder for the body to fight infection. For a closely related question about another antibiotic, see can you drink alcohol on amoxicillin. Many clinicians suggest avoiding alcohol until you feel better, and you should always follow the advice of your prescriber.
Caffeine and energy drinks
No established direct interaction. However, caffeine and some energy products can raise heart rate or cause palpitations, which can be confusing if you are watching for rhythm symptoms. Keep intake modest during an illness.
Birth control pills
Most antibiotics, apart from rifamycins such as rifampin, have not been shown to reduce the effectiveness of hormonal contraception, and azithromycin is not known to do so. But vomiting or severe diarrhea can interfere with absorption of any pill. If you have either, check your contraceptive’s instructions and use backup protection if advised.
Vitamins and mineral supplements
Vitamin C, vitamin D, zinc and iron are not known to bind azithromycin the way they bind some other antibiotics, but studies on specific combinations are limited. A simple approach is to take supplements a couple of hours apart from the antibiotic dose, particularly magnesium- or aluminum-containing products.
Probiotics
Antibiotics can disturb gut bacteria, and many people take probiotics to reduce diarrhea. If you do, taking the probiotic a couple of hours after the antibiotic is a common approach. Evidence for specific strains varies. Speak to your pharmacist if you are immunocompromised, because probiotics are not risk-free in that setting.
Herbal products
Herbals are less studied, but a few points are worth knowing:
- Licorice root in large amounts can lower potassium, which raises the risk of QT problems when paired with a QT-prolonging drug.
- St. John’s wort can induce drug-metabolizing enzymes and transporters. Its effect on azithromycin is not well characterized, but it interacts with many other medicines, so mention it to your pharmacist.
- Laxative teas and diuretic herbs can contribute to electrolyte loss.
Vaccines
Antibiotics can reduce the effectiveness of the oral live typhoid vaccine, which relies on living bacteria. If you are traveling and planning vaccines, tell the clinic about the antibiotic. Most other vaccines are not affected.
Conditions that change the interaction picture
| Condition | Why it matters with azithromycin |
|---|---|
| Long QT syndrome, heart failure, slow heart rate, recent heart attack | Higher baseline risk of dangerous rhythms |
| Low potassium or magnesium | Raises the risk of QT-related rhythm problems |
| Myasthenia gravis | Macrolides have been reported to worsen muscle weakness; labeling carries a warning |
| Liver disease | Azithromycin is cleared mainly through bile; caution is advised, and liver injury is a known rare effect |
| Kidney disease | Dose adjustments are not always needed, but interacting drugs like colchicine become riskier |
| History of C. difficile infection | All antibiotics raise the risk of this gut infection, so choice and duration deserve thought |
| Pregnancy and breastfeeding | Azithromycin is often used when a macrolide is needed, but decisions are individualized |
| Older age | More medicines, more QT-prone physiology, and more drug-level effects |
Step by step: how to check your own medicine list
- Write down everything you take. Include prescriptions, over-the-counter products, vitamins, herbals, patches, inhalers and occasional use items such as antacids, sleep aids and migraine remedies.
- Mark the “narrow margin” drugs: warfarin, digoxin, colchicine, cyclosporine, tacrolimus, lithium, anti-seizure drugs, heart rhythm medicines and chemotherapy drugs.
- Mark anything that affects the heart rhythm: antipsychotics, some antidepressants, methadone, ondansetron, other antibiotics, antimalarials and antiarrhythmics.
- Mark anything with magnesium, aluminum or calcium: antacids, laxatives, supplements.
- Note your health conditions, especially heart disease, electrolyte problems, liver or kidney disease and myasthenia gravis.
- Bring the list to the prescriber and pharmacist before the first dose, and use one pharmacy if possible so the record is complete.
- Ask about monitoring: whether you need an ECG, a blood test (INR, drug level, potassium or magnesium) or a symptom plan.
- Set a plan for timing of antacids, supplements and other medicines.
A short script for the pharmacy counter
If you are not sure what to say, you can adapt something like this:
“I’ve been prescribed azithromycin. I take [list]. I also have [heart condition, kidney problem, none]. Does anything on this list affect heart rhythm, blood thinning or drug levels? Do I need to separate any antacids or supplements, and is there anything I should watch for?”
Most pharmacists welcome this question, and it takes less than a minute.
Side effects that can look like an interaction
Common azithromycin side effects include nausea, diarrhea, stomach pain and vomiting. Less often, people notice headache, dizziness or taste changes. Rare but important effects include severe allergic reactions, serious skin reactions, liver injury, hearing changes and the heart rhythm effects described above. Persistent watery diarrhea during or after antibiotics, particularly with fever or abdominal pain, can signal C. difficile infection and needs medical attention.
It helps to separate “side effect of the antibiotic” from “problem with a combination.” If symptoms started after adding a new medicine or supplement, tell your pharmacist the timing. For general antibiotic side-effect patterns with a comparison drug, see amoxicillin side effects, and for how long a medicine lingers, see how long amoxicillin stays in your system. Azithromycin itself has a long half-life, roughly two to three days in tissues, so its effects and interaction potential can persist for days after the last tablet.
When to seek urgent care
- Fainting, near-fainting, a racing or irregular heartbeat, or chest discomfort
- Seizure
- Swelling of the face, lips or throat, trouble breathing, or a widespread rash, blistering or peeling skin
- Yellowing of the eyes or skin, dark urine, severe abdominal pain
- Severe or bloody diarrhea, especially with fever
- New muscle weakness, difficulty swallowing or breathing in someone with myasthenia gravis
- Signs of digoxin toxicity or bleeding if you take those drugs, such as black stools, blood in urine or unusual bruising
In the U.S., call your local emergency number. For questions about possible poisoning or overdose that are not emergencies, the Poison Help line is 1-800-222-1222, and you can find more at poison.org.
Using antibiotics wisely
Interactions are one reason to use antibiotics only when they are needed. The CDC’s page on antibiotic prescribing and use explains that antibiotics do not work against viruses such as colds and flu, and that unnecessary use drives resistance and side effects. If your prescription is for a condition such as a sore throat, ear infection or dental problem, it is fair to ask whether an antibiotic is required and whether alternatives exist. For examples of how choices differ, see amoxicillin for strep throat, amoxicillin for ear infections and amoxicillin for tooth infections. Take the full course as directed unless your prescriber tells you otherwise, and never share antibiotics.
Frequently asked questions
What medicines should not be taken with azithromycin?
There is no single “never” list for everyone, but the combinations that draw the most caution are other QT-prolonging drugs, ergot migraine medicines and drugs with narrow safety margins such as warfarin, digoxin, colchicine and transplant medicines. Aluminum and magnesium antacids should be spaced apart. Your pharmacist can check your list.
Can I take azithromycin with antacids like Tums or Maalox?
Aluminum- and magnesium-containing antacids (many Maalox- and Mylanta-type products) can reduce azithromycin’s peak levels, so they should not be taken at the same time. A common approach is to separate them by about two hours. Calcium carbonate products such as Tums are not specifically named in the usual labeling, but spacing them out is a reasonable precaution.
Can I drink alcohol while taking azithromycin?
There is no proven direct interaction, but alcohol can worsen nausea, dizziness and dehydration, and rest and hydration help recovery. Many clinicians advise skipping alcohol until you feel better. Follow your prescriber’s advice.
Do I need to avoid grapefruit or dairy?
Generally no. Azithromycin is not known to have a significant interaction with either. If you take other medicines that interact with grapefruit, keep avoiding it for those reasons.
Can I take azithromycin with ibuprofen or acetaminophen?
No significant interaction is commonly reported with either, and they are frequently used together for fever and aches. Check the labels for your own health conditions, such as kidney, stomach or liver problems.
Is azithromycin safe with antidepressants?
It depends on the antidepressant. Citalopram and escitalopram, some tricyclics and others can prolong QT, so a pharmacist should check the combination. Many others have little effect on heart rhythm. See Prozac drug interactions and Luvox drug interactions for more on antidepressants and combinations.
Does azithromycin interact with birth control?
Azithromycin is not known to reduce the effectiveness of hormonal contraception. Vomiting or severe diarrhea can reduce absorption of any pill, so follow your contraceptive’s instructions in those cases.
Can azithromycin cause a dangerous heart rhythm?
It can prolong the QT interval, and rare cases of dangerous rhythms have been reported. For most healthy people the risk is very low. It is higher with existing heart disease, low potassium or magnesium, or other QT-prolonging medicines, which is why those need review.
How long do interactions last after I finish the course?
Azithromycin has a long tissue half-life, so effects can persist for several days after the last dose. If you need to start a new medicine soon after finishing, mention the recent azithromycin to the prescriber.
What if I already took both and feel fine?
Most people who take a few interacting products do not have a problem, but do not assume you are in the clear. Call your pharmacist or prescriber, tell them what you took and when, and ask whether you need monitoring. If you develop palpitations, fainting, severe dizziness or other warning signs, seek urgent care.
The bottom line
Azithromycin is one of the more interaction-friendly antibiotics, which is part of why it is so widely used. The combinations that matter most involve heart rhythm, because of its effect on the QT interval, along with a short list of narrow-margin medicines such as warfarin, digoxin, colchicine and transplant drugs. Aluminum and magnesium antacids are best spaced apart. Most foods, dairy, grapefruit and common vitamins are minor issues.
The practical takeaway is simple: before the first dose, give your pharmacist your full medicine list, mention any heart condition or electrolyte problem, and ask what, if anything, needs monitoring or timing changes. A one-minute conversation covers the vast majority of the risk.
Medical disclaimer: This article is for general education and is not medical advice. It does not replace guidance from a doctor or pharmacist. Interaction information changes as new evidence emerges, so confirm details with a pharmacist and the current product label before starting, stopping or combining any medicine.
Sources and further reading
- DailyMed: current azithromycin (Zithromax) prescribing information
- FDA Drug Safety Communications: search “azithromycin” for the 2013 heart rhythm warning
- CredibleMeds: QT drug lists
- CDC: antibiotic prescribing and use
- Poison Help (America’s Poison Centers)
- Ray WA et al. Azithromycin and the risk of cardiovascular death. New England Journal of Medicine, 2012
