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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Limited Use [what does this mean?]
Generic drug name: azithromycin (a zyth row MY sin)
Brand name(s): ZITHROMAX, ZMAX
GENERIC: available FAMILY: Macrolides
Find the drug label by searching at DailyMed.

Limited Use [what does this mean?]
Generic drug name: clarithromycin (cla rith roe MY sin)
GENERIC: available FAMILY: Macrolides
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Clarithromycin caused fetal harm in animal studies, including heart and blood vessel defects, growth retardation, and cleft palate. Azithromycin was not tested properly. Because of the potential for serious adverse effects to the fetus, these drugs should not be used by pregnant women.

Breast-feeding Warning

Other drugs in this class are excreted in human milk. It is likely that these drugs are also excreted in human milk. Because of the potential for serious adverse effects in nursing infants, you should not take these drugs while nursing.

Safety Warnings For This Drug [top]

Antibiotic-Associated Diarrhea

Antibiotic-associated diarrhea (AAD) is quite common and its incidence varies from 5% to 20% of patients depending on which antibiotic they are taking, although practically all antibiotics have been associated with AAD. Fortunately, most cases are mild and self-limited, ending with the cessation of use of the offending antibiotic. The antibiotics most commonly associated with this mild form of AAD include ampicillin, amoxicillin, cephalosporins and clindamycin.[1] There have been studies in children or adults in which the use of prophylactic yogurt in people using antibiotics has significantly reduced the occurrence or severity of AAD.[2],[3] However, 10% to 20% of all patients who get AAD (0.5% to 4% of patients using antibiotics) will get the more severe form of AAD known as pseudomembranous colitis (see below). If you are taking any antibiotic and develop diarrhea after starting to use the drug, call your physician to discuss whether another antibiotic should be used and to discuss the need for rehydration due to the fluid loss from the diarrhea.

Pseudomembranous colitis has been reported with nearly all antibacterial agents and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.

Because antibiotic therapy has been associated with severe colitis, which may end fatally, it should be reserved for serious infections where less toxic antimicrobial agents are inappropriate, as described in the INDICATIONS AND USAGE section. It should not be used in patients with nonbacterial infections such as most upper respiratory tract infections. Treatment with antibacterial agents alters the normal flora of the colon and may permit over-growth of clostridia. Studies indicate that a toxin produced by Clostridium difficile is one primary cause of "antibiotic-associated colitis."

After the diagnosis of pseudomembranous colitis has been established, therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to drug discontinuation alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation, and treatment with an antibacterial drug that is clinically effective against C. difficile colitis.

Diarrhea, colitis, and pseudomembranous colitis have been observed to begin up to several weeks following cessation of therapy.

Facts About This Drug [top]

Azithromycin (ZITHROMAX, ZMAX) and clarithromycin (BIAXIN, BIAXIN-XL) are approved by the Food and Drug Administration (FDA) to treat bacterial infections in many parts of the body.[4],[5] These drugs will not help a cold but may be effective in the treatment of some cases of bronchitis and sinusitis.[6]

Clarithromycin is sometimes used in combination with other drugs to treat ulcers caused by Helicobacter pylori (see Combination Treatments for Helicobacter Pylori Infection).

Azithromycin ...

Azithromycin (ZITHROMAX, ZMAX) and clarithromycin (BIAXIN, BIAXIN-XL) are approved by the Food and Drug Administration (FDA) to treat bacterial infections in many parts of the body.[4],[5] These drugs will not help a cold but may be effective in the treatment of some cases of bronchitis and sinusitis.[6]

Clarithromycin is sometimes used in combination with other drugs to treat ulcers caused by Helicobacter pylori (see Combination Treatments for Helicobacter Pylori Infection).

Azithromycin and clarithromycin belong to the same family of antibiotics as erythromycin (E.E.S., E.E.S. 200, E.E.S. 400, ERYC, ERYPED, ERY-TAB, ERYTHROCIN, PCE, PEDIAMYCIN, PEDIAMYCIN 400). For many infections, azithromycin and clarithromycin are similar in effectiveness to amoxicillin (AMOXIL) and erythromycin. However, azithromycin and clarithromycin cost much more than these alternative antibiotics.

Because azithromycin is principally eliminated via the liver, you should ask your doctor whether this drug is right for you if your liver does not function normally.

Adverse effects

Macrolide antibiotics have been linked to an increased risk of QT prolongation, a change in the electrical activity of the heart that can lead to a fatal heart rhythm disturbance called torsades de pointes, resulting in sudden death.

Certain medications for treating abnormal heart rhythms, Alzheimer’s disease, bacterial infections, depression, fungal infections, HIV infection and overactive bladder can increase the risk of QT prolongation when taken together with clarithromycin.[7]


There have been post-marketing reports of colchicine (COLCRYS, a drug for treatment of gout) toxicity with the simultaneous use of clarithromycin and colchicine, especially in the elderly. Some of these events occurred in patients with renal (kidney) insufficiency. Deaths have been reported in some of these patients.[8]

In October 2014, JAMA Internal Medicine published a study showing that older patients taking one of two commonly used oral sulfonylurea diabetes drugs — glipizide (GLUCOTROL, GLUCOTROL XL) or glyburide (DIABETA, GLUCOVANCE, GLYNASE) — in combination with clarithromycin had an increased risk of developing dangerously low blood sugar levels, a condition known as hypoglycemia.[9]

Studies say...

Numerous studies have examined the effects of clarithromycin or azithromycin on heart disease, but so far the results have been mixed: Some studies find that these drugs increase deaths related to heart attacks, while others do not show a significant difference in deaths.[10],[11],[12] Because the studies are inconclusive, we recommend that individuals with heart disease use a different antibiotic whenever possible.

The New England Journal of Medicine (NEJM) published a study indicating that azithromycin (ZITHROMAX, ZMAX) may increase the risk of cardiovascular death, particularly sudden death from heart rhythm disturbances.[13] Based on this research and previous studies, azithromycin is thought to cause torsades de pointes, which can lead to sudden cardiac death, the most common cause of death in azithromycin users in the NEJM study. (See the "Adverse Effects" section for information on torsades de pointes.) The FDA-approved product labeling for azithromycin was updated in 2021 to include a warning that observational studies have shown an approximately twofold increased short-term potential risk of acute cardiovascular death in adults exposed to azithromycin compared with those treated without antibiotics, including amoxicillin (AMOXIL, LAROTID).[14]

In January 2016, an article published in the BMJ showed that clarithromycin use was associated with an increased risk of heart attack, abnormal heart rhythms and cardiac death.[15]

In 2010, Prescrire International published an article stating that neuropsychological disorders (hallucination, delirium, manic episodes and sometimes depression) have been associated with macrolide antibiotic use in both adults and children. The data were collected from several European countries, and the effects appeared to be rare and reversible upon drug withdrawal.[16]

In 2016, JAMA Internal Medicine published a study showing that clarithromycin use was associated with an increased risk of neuropsychiatric disorders. These risks include psychosis, delirium, mood disorders, sleep disturbances and cognitive impairment (such as problems with thinking, remembering information or making decisions). The risk was small and disappeared once the drug was stopped.[17]

In 2011, the Canadian Medical Association Journal published results from a Canadian study on the use of macrolide antibiotics and calcium channel blocker drugs in elderly patients. The study found that patients using this drug combination therapy experienced an increased risk of being hospitalized for hypotension (low blood pressure). According to the article, the risk of hypotension occurred with both erythromycin and clarithromycin.[18]

In 2013, the Journal of the American Medical Association published data from another Canadian study on the use of macrolide antibiotics and calcium channel blocker drugs. This study looked at the use of clarithromycin compared with azithromycin in elderly patients taking calcium channel blockers. The purpose of the study was to evaluate patients for the risk of hospitalization for acute kidney injury or hypotension, as well as all-cause mortality. The study showed that there were small but statistically significant greater risks of hospitalization for acute kidney injury or hypotension and of death in patients taking clarithromycin with a calcium channel blocker drug compared with those taking azithromycin with a calcium channel blocker.[19]

In 2013, the Annals of Internal Medicine published a study suggesting that patients older than 65 who take atorvastatin, lovastatin or simvastatin have a greater risk of statin-induced muscle damage if they take clarithromycin or erythromycin.[20]

In 2020, the BMJ published a study suggesting that children born to mothers who used macrolide antibiotics during pregnancy have an increased risk of birth defects.[21]

In 2024, Scientific Reports published an article showing that macrolide antibiotics are associated with an increased risk of hearing loss.[22]

Regulatory action surrounding azithromycin

2011: In January, the FDA updated the drug product label to include the following information: “Abnormal liver function, hepatitis, cholestatic jaundice, hepatic necrosis, and hepatic failure have been reported, some of which have resulted in death. Discontinue azithromycin immediately if signs and symptoms of hepatitis occur.”[23]

2012: In May, the FDA announced its review of information from the NEJM study on the risks of cardiovascular death in patients treated with azithromycin. The agency stated that it would continue to review the study results and would communicate its findings to the public.[24]

2013: In March, the FDA issued a follow-up to its May 2012 advisory, stating that azithromycin can cause abnormal changes in the electrical activity of the heart that may lead to a potentially fatal irregular heart rhythm.[25]

In May, Health Canada, the Canadian regulatory agency, announced that in patients who were at a higher risk of cardiovascular events, there was a small absolute increase in the risk of cardiovascular death when these patients took azithromycin.[26]

2015: An FDA advisory stated that using clarithromycin and quetiapine (SEROQUEL) together can result in increased toxicity of quetiapine.[27]

2018: The FDA reported that clarithromycin use in patients with heart disease can increase the risk of heart problems or death, which can occur years after use.[28]

In August, the FDA warned that when azithromycin is used for a long time to treat a lung condition in patients with cancers of the blood or lymph nodes who had a donor stem cell transplant, the risk of cancer relapse and death is increased.[29]

Before You Use This Drug [top]

Do not use if you have or have had:

  • hypersensitivity to clarithromycin, azithromycin, or erythromycin

Tell your doctor if you have or have had:

  • kidney or liver problems
  • pregnancy or are breast-feeding

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products.

When You Use This Drug [top]

  • Check with your doctor if there is no improvement within a few days or if condition becomes worse.
  • If you plan to have any surgery, including dental, tell your doctor that you take this drug.
  • Do not take with pimozide.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Take this drug for the prescribed length of time. If you stop too soon, your symptoms could come back.
  • Azithromycin capsules: Take with water only. Do not eat for about an hour before or two hours after taking this medication.
  • Azithromycin tablets: Take with or without food.
  • Clarithromycin: Take with or without food.
  • Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

ALFENTA, alfentanil, alprazolam, bromocriptine, carbamazepine, cilostazol, COUMADIN, cyclosporine, delavirdine, DETROL, digoxin, disopyramide, efavirenz, ELIXOPHYLLIN, ERGOMAR, ERGOSTAT, ergotamine, FORTOVASE, HALCION, INVIRASE, LANOXICAPS, LANOXIN, lovastatin, MEDROL, methylprednisolone, MEVACOR, mizolastine, MYCOBUTIN, nelfinavir, NEORAL, NORPACE, NORVIR, ORAP, PARLODEL, pimozide, PLETAL, PRANDIN, PRIFTIN, quinidine, QUINIDEX, repaglinide, RESCRIPTOR, RETROVIR, rifabutin, rifapentine, ritonavir, SANDIMMUNE, saquinavir, sildenafil, simvastatin, SLO-BID, SUSTIVA, tacrolimus, TEGRETOL, THEO-24, theophylline, tolterodine, triazolam, VIAGRA, VIRACEPT, warfarin, XANAX, zidovudine, ZOCOR.

Adverse Effects [top]

Call your doctor immediately if you experience:

  • severe, watery diarrhea (may be bloody)
  • skin rash or itching
  • difficulty breathing
  • fever
  • nausea or vomiting
  • abdominal tenderness
  • abdominal or stomach cramps or pain
  • joint pain
  • swelling of face, mouth, neck, hands, or feet
  • yellow eyes or skin
  • unusual bleeding or bruising

Call your doctor if these symptoms continue:

  • abdominal or stomach pain
  • dizziness
  • mild diarrhea
  • headache
  • nausea or vomiting
  • abnormal sense of taste (clarithromycin)

last reviewed April 30, 2024