Does Avelox (moxifloxacin) cause side effects?

Avelox (moxifloxacin) is a fluoroquinolone antibiotic used to treat infections caused by gram-positive and gram-negative bacteria like Streptococcus anginosus, Streptococcus constellatus, Streptococcus pneumonia, Enterobacter cloacae, Escherichia coli, Haemophilus influenza, Klebsiella pneumonia, Moraxella catarrhalis, Clostridium perfringens, Chlamydophila pneumonia, and Mycoplasma pneumonia.

Avelox works by blocking DNA gyrase enzyme, which is responsible for production and repair of bacterial DNA. Blocking of DNA gyrase leads to bacteria death and prevents worsening of infection. 

Common side effects of Avelox include

Serious side effects of Avelox include

Drug interactions of Avelox include aluminum and magnesium containing antacids, sucralfate, and multivitamins, because they can lower absorption of Avelox and reduce its effectiveness. They should be administered 4 hours before or 8 hours after Avelox.

Avelox should be used with caution with warfarin because Avelox can increase the effect of warfarin and risks of bleeding and bruising.

Avelox should be used with caution with sotalol because it can contribute to abnormal heart rhythm.

There are no adequate studies done on Avelox to determine safe and effective use in pregnant women. Avelox should only be used during pregnancy if clearly needed.

Avelox enters breast milk. Mothers should decide whether to stop breastfeeding or discontinue Avelox.

What are the important side effects of Avelox (moxifloxacin)?

Side effects of moxifloxacin are

Rare allergic reactions have been described, such as hives and anaphylaxis (shock). Moxifloxacin should be used with caution in patients with central nervous system diseases such as seizures, because rare seizures have been reported in patients receiving moxifloxacin.

Moxifloxacin should be avoided in children and adolescents less than 18 years of age, as safe use in these patients has not been established.

Moxifloxacin as well as other antibiotics in the fluoroquinolone class of antibiotics, has been associated with tendinitis and even rupture of tendons, particularly the Achilles tendon. This risk is especially increased in patients over 60 or patients taking corticosteroids ( for example prednisone).

Many antibiotics, including moxifloxacin, can alter the normal bacteria in the colon and encourage overgrowth of a bacterium responsible for the development of inflammation of the colon, (C. difficile or pseudomembranous colitis).

Patients who develop signs of pseudomembranous colitis after starting moxifloxacin (diarrhea, fever, abdominal pain, and possibly shock) should contact their physician immediately.

Fluoroquinolones have neuromuscular blocking activity and can worsen muscles weakness in individuals with myasthenia gravis. They also worsen low blood glucose levels when combined with sulfonylureas (for example, glyburide [Micronase, Diabeta, Glynase, Prestab]).

Avelox (moxifloxacin) side effects list for healthcare professionals

The following serious and otherwise important adverse reactions are discussed in greater detail in the product labeling:

  • Disabling and Potentially Irreversible Serious Adverse Reactions Including Tendinitis and Tendon Rupture, Peripheral Neuropathy, and Central Nervous System Effects
  • Tendinitis and Tendon Rupture
  • Peripheral Neuropathy
  • Central Nervous System Effects
  • Exacerbation of Myasthenia Gravis
  • QT Prolongation
  • Other Serious and Sometimes Fatal Adverse Reactions
  • Hypersensitivity Reactions
  • Clostridium difficile-Associated Diarrhea
  • Blood Glucose Disturbances
  • Photosensitivity/Phototoxicity
  • Development of Drug Resistant Bacteria

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The data described below reflect exposure to Avelox in 14981 patients in 71 active controlled Phase II-IV clinical trials in different indications.

  • The population studied had a mean age of 50 years (approximately 73% of the population was less than 65 years of age), 50% were male, 63% were Caucasian, 12% were Asian and 9% were Black.
  • Patients received Avelox 400 mg once daily oral, intravenous, or sequentially (intravenous followed by oral).
  • Treatment duration was usually 6 to 10 days, and the mean number of days on therapy was 9 days.
  • Discontinuation of Avelox due to adverse reactions occurred in 5% of patients overall, 4% of patients treated with 400 mg PO, 4% with 400 mg intravenous and 8% with sequential therapy 400 mg oral/intravenous.
  • The most common adverse reactions ( > 0.3%) leading to discontinuation with the 400 mg oral doses were nausea, diarrhea, dizziness, and vomiting.
  • The most common adverse reaction leading to discontinuation with the 400 mg intravenous dose was rash. The most common adverse reactions leading to discontinuation with the 400 mg intravenous/oral sequential dose were diarrhea, pyrexia.
  • Adverse reactions occurring in 1% of Avelox-treated patients and less common adverse reactions, occurring in 0.1 to 1% of Avelox-treated patients, are shown in Tables 2 and Table 3, respectively.
  • The most common adverse drug reactions (3%) are nausea, diarrhea, headache, and dizziness.

Table 2: Common (1% or more) Adverse Reactions Reported in Active-Controlled Clinical Trials with Avelox

System Organ ClassAdverse Reactions% (N=14,981)
Blood and Lymphatic System DisordersAnemia1
Gastrointestinal DisordersNausea7
Abdominal pain2
General Disorders and Administration Site ConditionsPyrexia1
InvestigationsAlanine aminotransferase increased1
Metabolism and Nutritional DisorderHypokalemia1
Nervous System DisordersHeadache4
Psychiatric DisordersInsomnia2

Table 3: Less Common (0.1 to less than 1%) Adverse Reactions Reported in Active-Controlled Clinical Trials with AVELOX (N=14,981)

System Organ ClassAdverse Reactions
Blood and Lymphatic System DisordersThrombocythemia
Cardiac DisordersAtrial fibrillation
Angina pectoris
Cardiac failure
Cardiac arrest
Ear and Labyrinth DisordersVertigo Tinnitus
Eye DisordersVision blurred
Gastrointestinal DisordersDry mouth
Abdominal discomfort
Abdominal distention
Gastroesophageal reflux disease
General Disorders and Administration Site Conditions

Chest pain
Infusion site extravasation
Chest discomfort
Facial pain

Hepatobiliary disordersHepatic function abnormal
Infections and InfestationsCandidiasis
Vaginal infection
Fungal infection
InvestigationsAspartate aminotransferase increased
Gamma-glutamyltransferase increased
Blood alkaline phosphatase increased Electrocardiogram
QT prolonged
Blood lactate dehydrogenase increased
Blood amylase increased
Lipase increased
Blood creatinine increased
Blood urea increased
Hematocrit decreased
Prothrombin time prolonged
Eosinophil count increased
Activated partial thromboplastin time prolonged
Blood triglycerides increased
Blood uric acid increased
Metabolism and Nutrition DisordersHyperglycemia
Decreased appetite
Musculoskeletal and Connective Tissue DisordersBack pain
Pain in extremity
Muscle spasms
Musculoskeletal pain
Nervous System DisordersDysgeusia
Psychiatric DisordersAnxiety
Confusional state
Renal and Urinary DisordersRenal failure
Reproductive System and Breast DisordersVulvovaginal pruritus
Respiratory, Thoracic, and Mediastinal DisordersDyspnea
Skin and Subcutaneous TissueRash
Dermatitis allergic
Night sweats
Vascular DisordersHypertension

Laboratory Changes

Changes in laboratory parameters, which are not listed above and which occurred in 2% or more of patients and at an incidence greater than in controls included: increases in mean corpuscular hemoglobin (MCH), neutrophils, white blood cells (WBCs), prothrombin time (PT) ratio, ionized calcium, chloride, albumin, globulin, bilirubin; decreases in hemoglobin, red blood cells (RBCs), neutrophils, eosinophils, basophils, glucose, oxygen partial pressure (Po2), bilirubin, and amylase.

It cannot be determined if any of the above laboratory abnormalities were caused by the drug or the underlying condition being treated.

Postmarketing Experience

Table 4 below lists adverse reactions that have been identified during post-approval use of Avelox. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Table 4: Postmarketing Reports of Adverse Drug Reactions

System Organ ClassAdverse Reactions
Blood and Lymphatic System DisordersAgranulocytosis Pancytopenia
Cardiac DisordersVentricular tachyarrhythmias (including in very rare cases cardiac arrest and torsade de pointes, and usually in patients with concurrent severe underlying proarrhythmic conditions)
Ear and Labyrinth DisordersHearing impairment, including deafness(reversible in majority of cases)
Eye DisordersVision loss (especially in the course of CNS reactions, transient in majority of cases)
Hepatobiliary DisordersHepatitis (predominantly cholestatic) Hepatic failure (including fatal cases) Jaundice Acute hepatic necrosis
Immune System DisordersAnaphylactic reaction Anaphylactic shock Angioedema (including laryngeal edema)
Musculoskeletal and Connective Tissue DisordersTendon rupture
Nervous System DisordersAltered coordination, abnormal gait, muscle weakness, peripheral neuropathy (that may be irreversible), polyneuropathy
Psychiatric DisordersPsychotic reaction (very rarely culminating in self-injurious behavior, such as suicidal ideation/thoughts or suicide attempts
Renal and Urinary DisordersInterstitial nephritis
Respiratory, Thoracic and Mediastinal DisordersAllergic pneumonitis
Skin and Subcutaneous Tissue DisordersPhotosensitivity/phototoxicity reaction Stevens-Johnson syndrome, toxic epidermal necrolysis

What drugs interact with Avelox (moxifloxacin)?

Antacids, Sucralfate, Multivitamins And Other Products Containing Multivalent Cations

  • Fluoroquinolones, including Avelox, form chelates with alkaline earth and transition metal cations.
  • Oral administration of Avelox with antacids containing aluminum or magnesium, with sucralfate, with metal cations such as iron, or with multivitamins containing iron or zinc, or with formulations containing divalent and trivalent cations such as didanosine buffered tablets for oral suspension or the pediatric powder for oral solution, may substantially interfere with the absorption of Avelox, resulting in systemic concentrations considerably lower than desired.
  • Therefore, Avelox should be taken at least 4 hours before or 8 hours after these agents.


  • Fluoroquinolones, including Avelox, have been reported to enhance the anticoagulant effects of warfarin or its derivatives in the patient population.
  • In addition, infectious disease and its accompanying inflammatory process, age, and general status of the patient are risk factors for increased anticoagulant activity.
  • Therefore the prothrombin time, International Normalized Ratio (INR), or other suitable anticoagulation tests should be closely monitored if Avelox is administered concomitantly with warfarin or its derivatives.

Antidiabetic Agents

  • Disturbances of blood glucose, including hyperglycemia and hypoglycemia, have been reported in patients treated concomitantly with fluoroquinolones, including Avelox, and an antidiabetic agent.
  • Therefore, careful monitoring of blood glucose is recommended when these agents are coadministered.
  • If a hypoglycemic reaction occurs, Avelox should be discontinued and appropriate therapy should be initiated immediately.

Nonsteroidal Anti-Inflammatory Drugs

Drugs That Prolong QT

  • There is limited information available on the potential for a pharmacodynamic interaction in humans between Avelox and other drugs that prolong the QTc interval of the electrocardiogram.
  • Sotalol, a Class III antiarrhythmic, has been shown to further increase the QTc interval when combined with high doses of intravenous Avelox in dogs.
  • Therefore, Avelox should be avoided with Class IA and Class III antiarrhythmics.

Treatment & Diagnosis

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Medically Reviewed on 8/27/2020
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Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.