Avelox (Moxifloxacin) 400mg: Dosing, Duration, Contraindications, and Adverse Effects
Adult Dosing Regimen
The standard adult dose of Avelox is 400 mg once daily, administered either orally or intravenously, with no dosage adjustment required for renal or hepatic impairment. 1
- Oral formulation: 400 mg tablets 1
- Intravenous formulation: 400 mg/250 mL solution for infusion 1
- Timing: Must be separated from multivalent cation-containing products (antacids, iron, zinc, magnesium, aluminum) by at least 4 hours before or 8 hours after to avoid absorption interference 2
- Important: Doses above 400 mg/day have limited long-term safety data and are not recommended 2
Treatment Duration by Indication
Treatment duration varies by infection type 1:
- Community-acquired pneumonia: 7-10 days 1
- Acute bacterial sinusitis: 7-10 days 1
- Acute bacterial exacerbation of chronic bronchitis: 5-7 days 1
- Complicated skin and skin structure infections: 7-14 days 1
- Plague: 10-14 days, starting as soon as possible after suspected exposure 2
- Non-tuberculous mycobacterial pulmonary disease: Extended therapy as part of combination regimen 1
Major Contraindications
Absolute Contraindications
Moxifloxacin is absolutely contraindicated in patients with hypersensitivity to moxifloxacin or other quinolones, and in those with significant cardiac conduction abnormalities. 1
Hypersensitivity: Known allergy to moxifloxacin or any quinolone antibiotic 1
Cardiovascular conditions 1:
- Congenital or documented acquired QT prolongation
- Clinically relevant bradycardia
- Clinically relevant heart failure with reduced left ventricular ejection fraction
- History of symptomatic arrhythmias
- Electrolyte disturbances, particularly uncorrected hypokalemia
Concurrent QT-prolonging medications: Should not be used with class IA and III antiarrhythmics 1
Special Population Contraindications
- Pregnancy: Avoid—animal studies show quinolones cause arthropathy 1
- Breastfeeding: Avoid—present in milk in animal studies 1
- Children and adolescents: Contraindicated in the UK for children or growing adolescents; arthropathy develops in weight-bearing joints in young animals 1
Relative Contraindications
- Severe liver disease: Particularly Child-Pugh severity score C and transaminase levels >5× upper limit of normal; consider levofloxacin as alternative 1
- History of tendon disorders: Especially quinolone-related tendon damage, age >60 years, or concomitant corticosteroid use 1
Major Adverse Effects
Common Adverse Effects
The most frequently reported adverse effects are generally mild to moderate 1, 3, 4, 5:
- Gastrointestinal: Nausea, vomiting, diarrhea 1, 5
- Hepatic: Transient increases in liver function tests 1
- Neurological: Dizziness, headache 1
- Cardiovascular: QTc prolongation (more common with hypokalemia, proarrhythmic conditions, or combination with other QT-prolonging drugs like ondansetron) 1, 6
Serious Adverse Effects (Rare but Life-Threatening)
The most critical serious adverse effects include QT prolongation with risk of arrhythmias, tendon rupture, and severe hypersensitivity reactions. 1
Cardiovascular
- QTc prolongation: Mean prolongation of 6 ± 26 milliseconds; risk increases with hypokalemia and predisposing cardiac conditions 1, 6
Musculoskeletal
- Tendon inflammation and rupture: Can occur within 48 hours of treatment or several months after stopping; increased risk in patients >60 years, history of tendon disorders, or concurrent corticosteroid use; cease all quinolone treatment immediately if tendinitis suspected 1
Dermatological
- Stevens-Johnson syndrome or toxic epidermal necrolysis (rare) 1
Hematological (Uncommon)
- Agranulocytosis, aplastic anemia, hemolytic anemia, thrombocytopenia 1
Hepatic
- Acute hepatitis (rare); fulminant hepatitis potentially leading to liver failure including fatal cases 1
Immunological
- Anaphylaxis, immune hypersensitivity (uncommon) 1
Metabolic
- Hypoglycemia (uncommon, particularly in patients on hypoglycemic drugs) 1
Neurological
- Seizures: Use caution in patients with CNS disorders 1
- Peripheral neuropathy: Sensorimotor polyneuropathy with paresthesias, hypoesthesias, dysesthesias, or weakness 1
Renal
- Renal impairment (rare) 1
Respiratory
- Extrinsic allergic alveolitis (rare) 1
Other
- Serum sickness (rare) 1
Required Monitoring
Baseline and ongoing monitoring is essential to detect serious adverse effects early. 1
- ECG monitoring: Baseline, at 2 weeks, and after addition of any new QT-prolonging medication 1
- Blood glucose: Regular monitoring in diabetic patients (risk of hypoglycemia) 1
- Routine toxicity monitoring: FBC (complete blood count), U&Es (electrolytes), LFTs (liver function tests) performed intermittently throughout treatment 1
- Drug level monitoring (when indicated): Target peak level 2.5-4 mg/L at 2 hours post-dose; repeat at 6 hours if delayed absorption suspected; indicated for known/suspected malabsorption or poor treatment response 1
Critical Drug Interactions
Moxifloxacin has several clinically significant drug interactions that require careful management. 1
- Antacids, iron, zinc: Reduced absorption of moxifloxacin—separate by 4-8 hours 1, 2
- Class IA and III antiarrhythmics, tricyclic antidepressants, macrolides, antipsychotics: Increased risk of QT prolongation—use with extreme caution 1
- NSAIDs: Increased risk of convulsions 1
- Pentamidine: Increased risk of ventricular arrhythmias 1
- Theophylline: Increased risk of convulsions; reduce theophylline dose and monitor levels 1