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Do NOT stop taking this or any drug without the advice of your physician. Some drugs can cause severe adverse effects when they are stopped suddenly.

Do Not Use [what does this mean?]
Generic drug name: moxifloxacin (mox ee FLOKS a sin)
Brand name(s): AVELOX
GENERIC: not available FAMILY: Fluoroquinolones
Find the drug label by searching at DailyMed.

Alternative Treatment [top]

Numerous other, safer antibiotics are approved to treat the same infections as this drug (see Fluoroquinolones).

Safety Warnings For This Drug [top]

FDA-Required Black-Box Warnings


  • Fluoroquinolones, including AVELOX, have been associated with disabling and potentially irreversible serious adverse reactions that have occurred together, including:
    • Tendinitis and tendon rupture
    • Peripheral neuropathy (nerve damage)
    • Central nervous system effects

Discontinue AVELOX immediately and avoid the use of fluoroquinolones, including AVELOX, in patients who experience any of these serious adverse reactions.

  • Fluoroquinolones, including AVELOX, may exacerbate muscle weakness in patients with myasthenia gravis. Avoid AVELOX in patients with known history of myasthenia gravis.
  • Because fluoroquinolones, including AVELOX, have been associated with serious adverse reactions, reserve AVELOX for use in patients who have no alternative treatment options for the following indications:
    • Acute bacterial sinusitis
    • Acute bacterial exacerbation of chronic bronchitis

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]

Moxifloxacin (AVELOX), part of the family of antibiotics known as fluoroquinolone antibiotics, was approved by the Food and Drug Administration (FDA) on Dec. 10, 1999.

Public Citizen lists moxifloxacin as a Do Not Use drug because it can cause 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. Patients who already have some degree of QT prolongation or who have...

Moxifloxacin (AVELOX), part of the family of antibiotics known as fluoroquinolone antibiotics, was approved by the Food and Drug Administration (FDA) on Dec. 10, 1999.

Public Citizen lists moxifloxacin as a Do Not Use drug because it can cause 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. Patients who already have some degree of QT prolongation or who have hypokalemia (low blood potassium levels) are at the greatest risk of sudden death when taking moxifloxacin.

The FDA’s Anti-Infective Drugs Advisory Committee voted 7-3 to recommend approval of the drug as long as its product label warned of heart problems. One concerned committee member who voted against the drug’s approval said: “I think there are enough things that really haven’t been answered [about moxifloxacin]... and I’m not sure I see what this drug adds to drugs we already have that’s so unique that we need this drug, that we absolutely need it, and we need it now for some indication [use].”[4]

Public Citizen agrees with this committee member’s assessment of moxifloxacin. There are numerous antibiotics available that treat the same infections moxifloxacin does but do not dangerously alter the heart’s electrical activity. We do not need more new drugs; we need better new drugs that are safer and more effective than those we already have. Unfortunately, there is nothing in U.S. drug law that requires a new drug to be either safer or more effective than drugs already on the market.

The FDA did heed the advisory committee’s advice and required a boldface warning notifying doctors and pharmacists of moxifloxacin’s heart effects and potentially life-threatening drug interactions.

Adverse effects

A January 2011 article in Prescrire International examined the formulation of intravenous (IV) moxifloxacin versus oral moxifloxacin. The article stated that, of all the fluoroquinolone antibiotics, moxifloxacin has been shown to have more adverse effects and has not been shown to be more effective. The article also stated that, in clinical trials, some of the adverse effects of moxifloxacin occurred more frequently with the IV formulation than with the oral formulation.[5]

In 2009, Prescrire International published an article on the use of moxifloxacin for pelvic inflammatory disease that listed this indication as “not acceptable.” As in the 2011 study, the authors of the article stated that moxifloxacin has a high incidence of adverse effects to which patients should not be exposed. Currently, the use of moxifloxacin is restricted and the precautions are strengthened based on these adverse effects.[6]

Prescrire International published another article in 2009 highlighting moxifloxacin’s increased risk of adverse effects — including cardiac disorders, liver disorders and cutaneous (skin) reactions — and stating that it offers no proven advantage over the other fluoroquinolones. The authors of the article concluded that:

Moxifloxacin carries an increased risk of fatal adverse effects and yet is no more effective than other fluoroquinolones. ...The best way to protect patients is to simply take moxifloxacin off the market.[7]


Irregular heartbeat

The FDA’s adverse drug reaction database contains multiple reports of heart rhythm disturbances, QT prolongation and torsades de pointes with use of moxifloxacin. Some patients experienced more than one of these problems.

The drug's labeling states that the effect of moxifloxacin in patients with inherited QT prolongation has not been studied; however, it is expected that these individuals may be more susceptible to drug-induced QT prolongation. The only way to know if you have inherited QT prolongation is for a doctor to perform an EKG. Moxifloxacin’s labeling also says that, because of limited clinical experience, the drug should be used with caution in patients with conditions that increase the risk of heart rhythm disturbances, such as a clinically significant slow heart rate (bradycardia) and acute blockage or narrowing of the blood vessels in the heart, known as myocardial ischemia.

Antibiotic-associated diarrhea (AAD)

AAD is a common adverse effect of antibiotic treatment. A report appearing in the Oct. 25, 2005, Canadian Medical Association Journal estimated that since 2003, as many as 2,000 patients may have died from AAD in Quebec hospitals.[8] Many different types of antibiotics can cause AAD, but reports have recently implicated the use of drugs in the fluoroquinolone family of antibiotics as an important risk factor in the development of a potentially life-threatening form of AAD called pseudomembranous colitis, which is caused by a type of bacteria called Clostridium difficile.

Convulsions and central nervous system (CNS) effects

Moxifloxacin shares the potential for many other serious adverse effects with the other members of the fluoroquinolone family of antibiotics. Convulsions have been reported in patients receiving fluoroquinolones. These drugs also can cause CNS adverse effects, including dizziness, confusion, tremors, hallucinations, depression and suicidal thoughts or acts. These adverse reactions may occur after the first dose. The use of nonsteroidal anti-inflammatory drugs — such as ibuprofen (MOTRIN), celecoxib (CELEBREX) and rofecoxib (VIOXX) — with a fluoroquinolone antibiotic may increase the risk of CNS stimulation and convulsions.

Nerve damage and tendon rupture

Peripheral neuropathy (nerve damage) and tendon ruptures have been reported in patients receiving fluoroquinolones. The FDA now requires that the product labels for all fluoroquinolone antibiotics must warn about the possibility of peripheral neuropathy and tendon rupture. See the boxed warnings under “Safety Warnings for These Drugs” (at the top of this page) for more information.[9]

Retinal detachment

A study published in the Journal of the American Medical Association (JAMA) found that patients taking oral fluoroquinolones appear to have an increased risk of developing retinal detachment, a medical emergency that can result in permanent vision loss unless promptly treated by an ophthalmologist. The authors of this study estimated that as many as 1,400 cases of retinal detachment each year in the U.S. may be due to the use of these drugs.[10]

Effects on blood sugar levels

In 2013, a study conducted in diabetic patients found an increased risk of abnormal blood sugar levels in diabetic patients using oral fluoroquinolones.[11]

In 2014, the FDA issued an advisory stating that the agency had received reports of irregularities in blood sugar, including hyperglycemia (high blood sugar levels) and hypoglycemia (low blood sugar levels), associated with moxifloxacin.[12]

Aortic aneurysm or dissection

An article published in JAMA Internal Medicine in 2015 warned that oral fluoroquinolone use was associated with an increased risk of aortic aneurysm or dissection. An aneurysm (bulge) or dissection (tear) in the wall of the aorta (blood vessel) can grow and burst, causing bleeding and even death.[13]

In March 2018, the BMJ published a study on the increased risk of aortic aneurysm or aortic dissection with fluoroquinolone use.[14]

Interactions with other drugs

Moxifloxacin should not be prescribed along with certain drugs used to treat heart rhythm disturbances, including amiodarone (CORDARONE), bretylium, disopyramide (NORPACE), moricizine (ETHMOZINE), procainamide (PROCANBID), quinidine (DURAQUIN, QUINAGLUTE DURA-TABS, QUINIDEX) and sotalol (BETAPACE).

The product label for moxifloxacin also warns that the drug has not been studied with other drugs that cause QT prolongation and should be used with caution when given together with erythromycin (E.E.S., ERYTHROCIN), antipsychotic drugs such as thioridazine (MELLARIL) and tricyclic antidepressants such as amitriptyline (ELAVIL) and imipramine (TOFRANIL). We do not think it is worth the risk of taking moxifloxacin together with these drugs when there are other antibiotics that can be used safely.

As of Jan. 15, 2004, Health Canada, an agency similar to the FDA, received 57 reports of suspected interactions between fluoroquinolones and the oral anticoagulant warfarin (COUMADIN, JANTOVEN). If you take warfarin and are prescribed a fluoroquinolone antibiotic, ask your doctor what tests should be performed to monitor your blood coagulation levels.[15]

Regulatory actions surrounding moxifloxacin

2006: We filed a petition with the FDA on Aug. 29, 2006, urging the agency to immediately warn consumers about the risks of tendinitis and tendon rupture associated with the use of fluoroquinolone antibiotics.

The petition called on the FDA to add a black-box warning, the strongest type of warning the FDA can require, to the product labels of all fluoroquinolone antibiotics, alerting health care professionals to the risks of using the drugs.

In addition, the petition asked that a “Dear Doctor" letter be sent to warn physicians about these potentially serious adverse drug reactions.

The petition also requested that the FDA require pharmacists to distribute FDA-approved Medication Guides informing consumers about the potential tendon damage that can result from use of these antibiotics and what steps to take if unexplained tendon pain should develop.[16]

2008: After being sued by Public Citizen because it did not respond to our 2006 petition, the FDA updated the product labels on fluoroquinolones to include a black-box warning with information about the increased risk of developing tendinitis and tendon rupture. The FDA also required manufacturers to develop a Medication Guide for patients.[17]

2011: The FDA added a black-box warning to the product labels for the fluoroquinolone group of drugs stating that when fluoroquinolones are used in patients with myasthenia gravis (a disease that causes muscle weakness), the drugs may exacerbate muscle weakness.[18]

The 2011 warning also required that information about this newer risk be provided in the above-mentioned FDA-approved Medication Guide that is issued when the prescription is filled.

2012: In August, the FDA updated the drug product information of AVELOX concerning the symptoms of polyneuropathy (nerve damage affecting several nerves). To prevent the development of irreversible conditions of neuropathy in patients using AVELOX, the drug should be discontinued if the patient experiences symptoms of neuropathy.[19]

2016: The FDA updated the drug product label for fluoroquinolones to warn that these drugs are associated with disabling and potentially permanent adverse effects of the tendons, muscles, joints, nerves and central nervous system.[20] The FDA also required that the new black-box warnings and other sections of the labeling for all oral and intravenous fluoroquinolones advise doctors not to prescribe the antibiotics to patients who have other treatment options for the following three common infections:

  • Acute bacterial exacerbation of chronic bronchitis (a type of chronic obstructive pulmonary disease, or COPD)
  • Acute uncomplicated bladder infection
  • Acute sinusitis

2018: The FDA strengthened the warning on the drug product labels of fluoroquinolones to warn that these drugs can cause low blood sugar (hypoglycemia) and psychiatric adverse effects.[21]

The FDA updated the product labels of fluoroquinolones to warn that fluoroquinolone use has been associated with an increased risk of aortic aneurysm or dissection, which can lead to bleeding and death.[22]

2020: In December, the Medicines and Healthcare products Regulatory Agency (MHRA, a regulatory agency in the U.K. similar to the FDA) issued an advisory that fluoroquinolones are associated with a small risk of a heart valve defect called heart valve regurgitation, which occurs when the heart valves do not close completely, allowing blood to flow in the wrong direction.[23] Such heart valve problems may lead to heart failure.

2023: The Medicines and Healthcare products Regulatory Agency (MHRA), agency in the U.K. similar to the FDA, issued an advisory reminder on the risk of psychiatric reactions associated with fluoroquinolones.[24]

last reviewed October 31, 2023