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Avelox Side Effects

Generic name: moxifloxacin

Medically reviewed by Last updated on Nov 30, 2022.

Note: This document contains side effect information about moxifloxacin. Some dosage forms listed on this page may not apply to the brand name Avelox.

Applies to moxifloxacin: oral tablet. Other dosage forms:


Oral route (Tablet)

Fluoroquinolones, including moxifloxacin, are associated with disabling and potentially irreversible serious adverse reactions that have occurred together, including tendinitis and tendon rupture, peripheral neuropathy, and CNS effects. Discontinue moxifloxacin and avoid use of fluoroquinolones in patients with these serious adverse reactions. Reserve use of moxifloxacin for patients with no alternative treatment options for acute bacterial sinusitis or acute bacterial exacerbation of chronic bronchitis. Fluoroquinolones, including moxifloxacin, may exacerbate muscle weakness in persons with myasthenia gravis. Avoid in patients with known history of myasthenia gravis.

Serious side effects of Avelox

Along with its needed effects, moxifloxacin (the active ingredient contained in Avelox) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking moxifloxacin:


  • Black, tarry stools
  • bleeding gums
  • blisters
  • bloating or swelling of the face, arms, hands, lower legs, or feet
  • blood in the urine or stools
  • blurred vision
  • bone pain
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • chest pain or tightness
  • chills
  • clay-colored stools
  • cough
  • crying
  • dark urine
  • deep or fast breathing with dizziness
  • diarrhea, watery and severe, which may also be bloody
  • difficult or labored breathing
  • difficulty with moving
  • difficulty with swallowing
  • discouragement
  • dizziness, fainting, or lightheadedness when getting up suddenly from a lying or sitting position
  • dry mouth
  • excessive muscle tone
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling of unreality
  • feeling of warmth or heat
  • feeling sad or empty
  • fever
  • fruit-like breath odor
  • headache
  • increased hunger
  • increased sensitivity of the skin to sunlight
  • increased thirst
  • increased urination
  • irregular heartbeat, recurrent
  • irritability
  • itching, skin rash
  • joint pain, stiffness, or swelling
  • lack of coordination
  • loss of appetite
  • loss of interest or pleasure
  • lower back, side, or stomach pain
  • mood or mental changes
  • muscle cramps, pains, stiffness, tension, or tightness
  • nausea
  • nervousness
  • noisy breathing
  • numbness of the feet, hands, and around the mouth
  • pain in the pelvis
  • pain, warmth, or burning in the fingers, toes, and legs
  • painful or difficult urination
  • pale skin
  • pinpoint red spots on the skin
  • pounding in the ears
  • problems with speech or speaking
  • problems with vision or hearing
  • quick to react or overreact emotionally
  • rapid weight gain
  • rapidly changing moods
  • redness or other discoloration of the skin
  • restlessness
  • seeing, hearing, or feeling things that are not there
  • seizures
  • sensation of the skin burning
  • sense of detachment from self or body
  • severe sunburn
  • shakiness in the legs, arms, hands, or feet
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • stomach cramps or tenderness
  • sweating
  • swelling of the feet or lower legs
  • swelling or puffiness of the face
  • swollen glands
  • thick, white vaginal discharge with no odor or with a mild odor
  • tingling of the hands or feet
  • trouble concentrating
  • trouble sleeping
  • unexplained weight loss
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • vomiting
  • vomiting of blood
  • white patches in the mouth or on the tongue
  • yellow eyes or skin

Incidence not known

  • Blistering, peeling, or loosening of the skin
  • burning, numbness, tingling, or painful sensations
  • change in the ability to see colors, especially blue or yellow
  • difficulty with chewing or talking
  • double vision
  • drooping eyelids
  • eye pain
  • general feeling of tiredness or weakness
  • hives
  • hoarseness
  • irregular or slow heart rate
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or genitals
  • light-colored stools
  • loss of consciousness
  • muscle weakness
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • severe headache
  • severe tiredness
  • stomach pain, continuing
  • unsteadiness or awkwardness
  • unusual behavior, including disorientation to time or place, failure to recognize people, hyperactivity, or restlessness

Other side effects of Avelox

Some side effects of moxifloxacin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:


  • Bad, unusual, or unpleasant (after) taste
  • belching
  • burning feeling in the chest or stomach
  • change in sense of smell
  • change in taste
  • changes in vision
  • continuing ringing or buzzing or other unexplained noise in the ears
  • difficulty having a bowel movement
  • excess air or gas in the stomach or bowels
  • fear or nervousness
  • feeling of constant movement of self or surroundings
  • full feeling
  • general feeling of discomfort or illness
  • hearing loss
  • heartburn
  • impaired vision
  • indigestion
  • itching of the vagina or genital area
  • lack or loss of strength
  • loss of memory
  • pain during sexual intercourse
  • passing of gas
  • problems with memory
  • redness, swelling, or soreness of the tongue
  • sensation of spinning
  • sleepiness or unusual drowsiness
  • sore mouth or tongue
  • stomach discomfort, upset, or pain

For Healthcare Professionals

Applies to moxifloxacin: injectable solution, intravenous solution, oral tablet.


The most common side effects were nausea, diarrhea, headache, and dizziness. This drug was discontinued due to side effects in 5% of patients overall, 4% of patients using 400 mg orally, 4% using 400 mg IV, and 8% using 400 mg IV/oral sequential therapy. The most common side effects leading to discontinuation with the oral dose were nausea, diarrhea, dizziness, and vomiting. The most common side effect leading to discontinuation with the IV dose was rash. The most common side effects leading to discontinuation with the IV/oral sequential dose were diarrhea and pyrexia.[Ref]


Decreased amylase has been reported in at least 2% of patients; however, it has not been determined if this laboratory abnormality was due to the drug or the underlying condition being treated.

Antibiotic-associated colitis (including pseudomembranous colitis; associated with life-threatening complications in very rare cases) was reported more often with IV therapy (with or without subsequent oral therapy).

The onset of pseudomembranous colitis symptoms has been reported during or after antimicrobial treatment.[Ref]

Common (1% to 10%): Nausea, diarrhea, vomiting, constipation, gastrointestinal pain, abdominal pain, dyspepsia, decreased amylase

Uncommon (0.1% to 1%): Dry mouth, abdominal discomfort, abdominal distention, gastritis, gastroesophageal reflux disease, gastroenteritis, flatulence, increased blood amylase, increased lipase, antibiotic-associated colitis (including pseudomembranous colitis, life-threatening complications)

Rare (0.01% to 0.1%): Dysphagia, stomatitis

Frequency not reported: Clostridium difficile-associated diarrhea, gastrointestinal disorder, pseudomembranous colitis, glossitis, tongue discoloration, upper abdominal pain, oral candidiasis, oral fungal infection[Ref]

Nervous system

Seizures (including grand mal convulsions) were reported more often with IV therapy (with or without subsequent oral therapy).

Cases of sensory or sensorimotor axonal polyneuropathy (affecting small and/or large axons) resulting in paresthesias, hypoesthesias, dysesthesias, and weakness have been reported.

Disturbed coordination leading to fall with injuries was reported, particularly in elderly patients.

Peripheral neuropathy (may be irreversible), polyneuropathy, hearing impairment (including deafness; reversible in most cases), and exacerbation of myasthenia gravis have also been reported during postmarketing experience.[Ref]

Common (1% to 10%): Headache, dizziness

Uncommon (0.1% to 1%): Somnolence, tremor, dysgeusia, lethargy, paresthesia, dysesthesia, hypoesthesia, syncope (i.e., acute and short-lasting loss of consciousness), tinnitus, vertigo, convulsions/seizures of various clinical manifestations (including grand mal convulsions), taste disorder, sleep disorders

Rare (0.01% to 0.1%): Smell disorders (including anosmia), disturbed coordination (including gait disturbances, especially due to dizziness or vertigo), disturbed attention, speech disorders, amnesia, peripheral neuropathy, polyneuropathy, hearing impairment (including deafness; usually reversible)

Very rare (less than 0.01%): Ageusia, hyperesthesia, exacerbation of myasthenia gravis

Frequency not reported: Aphasia, incoordination, parosmia, abnormal thinking, sensory axonal polyneuropathy, sensorimotor axonal polyneuropathy, orofacial dyskinesia, taste loss, taste perversion, tension headache

Postmarketing reports: Altered coordination, disturbed coordination (leading to fall with injuries), abnormal gait

Other fluoroquinolones:

-Very rare (less than 0.01%): Increased intracranial pressure (including pseudotumor cerebri)[Ref]


Common (1% to 10%): QT prolongation

Uncommon (0.1% to 1%): Atrial fibrillation, palpitations, tachycardia, angina pectoris, cardiac failure, cardiac arrest, bradycardia, hypertension, hypotension, phlebitis, increased blood pressure, prolonged ECG QT interval, ventricular tachyarrhythmias, vasodilation

Very rare (less than 0.01%): Unspecified arrhythmias, torsade de pointes, cardiac arrest, vasculitis

Frequency not reported: Abnormal ECG, arrhythmias, atrial flutter, ST-T wave changes, supraventricular tachycardia, ventricular extrasystoles, ventricular tachycardia, congestive cardiac failure[Ref]

QT prolongation was commonly reported in patients with hypokalemia, otherwise, it was uncommon.

Ventricular tachyarrhythmias and hypotension were reported more often with IV therapy (with or without subsequent oral therapy).

The mean QTc interval prolongation in a study of 787 patients using oral moxifloxacin was 6 msec versus 1 msec for a comparator group of patients using another antibiotic. There were 38 outliers in the moxifloxacin group (QTc interval greater than 450 msec for men or 470 msec for women) versus 28 outliers in the comparator group.

In another study (n=48), there were greater increases in the QT and QTc interval with 800 mg moxifloxacin than with 1000 mg levofloxacin or 1500 mg ciprofloxacin.

Elderly patients experienced more ECG abnormalities than younger patients.

Ventricular tachyarrhythmias (including very rare cases of cardiac arrest and torsade de pointes) have also been reported during postmarketing experience, usually in patients with concurrent severe underlying proarrhythmic conditions (e.g., clinically significant bradycardia, acute myocardial ischemia).[Ref]


Increased MCH, neutrophils, WBCs, albumin, and PT ratio, and decreased hemoglobin, RBCs, neutrophils, eosinophils, basophils, and PT ratio have been reported in at least 2% of patients; however, it has not been determined if these laboratory abnormalities were due to the drug or the underlying condition being treated.

Agranulocytosis has also been reported during postmarketing experience.[Ref]

Common (1% to 10%): Anemia, increased mean corpuscular hemoglobin (MCH), increased neutrophils, increased WBCs, increased albumin, increased prothrombin time (PT) ratio, decreased hemoglobin, decreased RBCs, decreased neutrophils, decreased eosinophils, decreased basophils

Uncommon (0.1% to 1%): Prolonged PT/INR increased, thrombocythemia, eosinophilia, neutropenia, thrombocytopenia, leukocytosis, leukopenia, decreased hematocrit, increased eosinophil count, prolonged activated partial thromboplastin time

Rare (0.01% to 0.1%): Abnormal thromboplastin level

Very rare (less than 0.01%): Increased prothrombin level/decreased INR, abnormal prothrombin level/INR, agranulocytosis

Frequency not reported: Decreased thromboplastin, decreased prothrombin/increased INR, increased platelet count, decreased hemoglobin, increased white blood cell count, decreased PT ratio

Postmarketing reports: Pancytopenia

Other fluoroquinolones:

-Very rare (less than 0.01%): Hemolytic anemia[Ref]


Common (1% to 10%): Increased ALT, increased bilirubin, decreased bilirubin, increased GGT, increased transaminases

Uncommon (0.1% to 1%): Abnormal hepatic function, increased aspartate aminotransferase, hepatic impairment (including increased lactate dehydrogenase)

Rare (0.01% to 0.1%): Jaundice, hepatitis (primarily cholestatic)

Very rare (less than 0.01%): Fulminant hepatitis (potentially leading to life-threatening liver failure [including fatal cases])

Frequency not reported: Acute fulminant hepatic failure, acute liver injury, abnormal liver function test, increased hepatic enzyme

Postmarketing reports: Hepatic failure (including fatal cases), acute hepatic necrosis[Ref]

Increased and decreased bilirubin levels have been reported in at least 2% of patients; however, it has not been determined if these laboratory abnormalities were due to the drug or the underlying condition being treated.

Increased GGT was reported more often with IV therapy (with or without subsequent oral therapy).

A 69-year-old male developed jaundice, pruritus, weight loss, dark urine, elevated lever function tests (total bilirubin: 28.45 mg/dL; conjugated bilirubin: 20.6 mg/dL; alkaline phosphatase: 249 units/L; ALT: 58 units/L) 3 weeks after a 5-day course of oral moxifloxacin. A liver biopsy showed portal inflammatory infiltrates with lymphocytes and eosinophils and predominantly casts in canaliculi. Liver function tests normalized over 2 months.

A 23-year-old female developed acute fulminant hepatitis (transaminases up to 8500 units/L) with hepatocellular necrosis, toxic epidermal necrolysis, and encephalopathy after 3 days of therapy. The condition culminated in multiple organ failure, acute respiratory distress syndrome, and death, despite a liver transplant.

Hepatitis (primarily cholestatic) and jaundice have also been reported during postmarketing experience.[Ref]


Common (1% to 10%): Hypokalemia, decreased glucose, decreased oxygen partial pressure (pO2)

Uncommon (0.1% to 1%): Hyperglycemia, anorexia, hyperlipidemia, decreased appetite, dehydration, increased blood uric acid, decreased food intake

Rare (0.01% to 0.1%): Hyperuricemia

Very rare (less than 0.01%): Hypoglycemia

Frequency not reported: Increased blood glucose

Postmarketing reports: Dehydration (secondary to diarrhea or reduced fluid intake)

Other fluoroquinolones:

-Very rare (less than 0.01%): Hypernatremia, hypercalcemia[Ref]

Increased ionized calcium, chloride, and globulin, and decreased glucose, and pO2 have been reported in at least 2% of patients; however, it has not been determined if these laboratory abnormalities were due to the drug or the underlying condition being treated.

Hypoglycemia has also been reported during postmarketing experience.[Ref]


Common (1% to 10%): Pyrexia, increased ionized calcium, increased chloride, increased globulin, superinfections (due to resistant bacteria or fungi [e.g., oral and vaginal candidiasis])

Uncommon (0.1% to 1%): Fatigue, chest pain, asthenia, unspecific pain, malaise, edema, chills, chest discomfort, increased blood alkaline phosphatase, increased blood LDH, increased blood triglycerides, candidiasis, fungal infection, facial pain, feeling unwell (primarily asthenia or fatigue), painful conditions (including pain in back, chest, pelvic, extremities)

Frequency not reported: Abnormal laboratory test (not specified), face edema, peripheral edema, weakness[Ref]

Edema was reported more often with IV therapy (with or without subsequent oral therapy).[Ref]


Hallucination was reported more often with IV therapy (with or without subsequent oral therapy).

Psychotic reactions and/or depression, very rarely culminating in self-injurious behavior (such as suicidal ideation/thoughts or suicide attempts), have been reported during postmarketing experience.[Ref]

Common (1% to 10%): Insomnia

Uncommon (0.1% to 1%): Nervousness, confusional state, psychomotor hyperactivity/agitation, depression, restlessness, disorientation, anxiety, hallucinations

Rare (0.01% to 0.1%): Abnormal dreams, emotional lability

Very rare (less than 0.01%): Depersonalization, psychotic reactions

Frequency not reported: Self-endangering behavior

Postmarketing reports: Self-injurious behavior (e.g., suicidal ideation/thoughts, suicide attempts)[Ref]


Common (1% to 10%): Injection site reactions, infusion site reactions

Uncommon (0.1% to 1%): Infusion site extravasation, infusion site thrombophlebitis/phlebitis[Ref]


Tendon rupture has also been reported during postmarketing experience.[Ref]

Uncommon (0.1% to 1%): Arthralgia, myalgia, muscle spasms, musculoskeletal pain

Rare (0.01% to 0.1%): Tendinitis, increased muscle tone and cramping, muscle weakness, muscle cramp, muscle twitching

Very rare (less than 0.01%): Arthritis, tendon rupture, muscle rigidity

Frequency not reported: Hypertonia, tendon disorder, musculoskeletal chest pain

Postmarketing reports: Gait disturbance (due to muscular, tendon, or joint symptoms)

Other fluoroquinolones:

-Very rare (less than 0.01%): Rhabdomyolysis[Ref]


Uncommon (0.1% to 1%): Allergic reaction

Rare (0.01% to 0.1%): Anaphylactic/anaphylactoid reaction, allergic edema/angioedema (including laryngeal edema; potentially life-threatening)

Very rare (less than 0.01%): Anaphylactic/anaphylactoid shock (potentially life-threatening)[Ref]

Anaphylactic reaction, anaphylactic shock, and angioedema (including laryngeal edema) have also been reported during postmarketing experience.[Ref]


Uncommon (0.1% to 1%): Rash, pruritus, hyperhidrosis, erythema, allergic dermatitis, night sweats, urticaria, dry skin

Very rare (less than 0.01%): Bullous skin reactions (like Stevens-Johnson syndrome or toxic epidermal necrolysis; potentially life-threatening)

Frequency not reported: Maculopapular rash, purpuric rash, pustular rash

Postmarketing reports: Toxic epidermal necrolysis, photosensitivity/phototoxicity reactions, Stevens-Johnson syndrome[Ref]


Uncommon (0.1% to 1%): Dysuria, vaginal infection, vulvovaginal pruritus

Frequency not reported: Vaginitis, vulvovaginal candidiasis, vulvovaginal mycotic infection[Ref]


Uncommon (0.1% to 1%): Visual disturbances (including blurred vision, diplopia; especially during central nervous system [CNS] reactions)

Rare (0.01% to 0.1%): Photophobia

Very rare (less than 0.01%): Transient vision loss (especially during CNS reactions), uveitis, bilateral acute iris transillumination

Frequency not reported: Amblyopia, abnormal vision (visual disturbances temporally associated with CNS symptoms)[Ref]

Vision loss (especially during CNS reactions) has also been reported during postmarketing experience; most cases were transient.[Ref]


Uncommon (0.1% to 1%): Increased blood creatinine, increased blood urea, renal failure, renal impairment (including increased BUN, increased creatinine)

Frequency not reported: Abnormal kidney function, acute renal failure

Postmarketing reports: Interstitial nephritis[Ref]

Renal impairment (including increased BUN and creatinine) and renal failure (due to dehydration, particularly in elderly patients with preexisting renal disorders) were reported more often with IV therapy (with or without subsequent oral therapy).[Ref]


Uncommon (0.1% to 1%): Dyspnea (including asthmatic conditions), wheezing, bronchospasm, asthma

Postmarketing reports: Allergic pneumonitis, laryngeal edema[Ref]


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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.