Drug reference

Moxifloxacin

Fluoroquinolone · Antibiotic

Also known as Moxifloxacin Hydrochloride

START

Confirm indication and rule out safer alternatives. Baseline ECG (QTc), electrolytes (K+, Mg2+, Ca2+), LFTs. Check for QT-prolonging medications, tendon risk factors (age >60, corticosteroids). Reserve for situations where beta-lactams/macrolides are contraindicated or failed.

TYPICAL MAX

400 mg/day (all indications); no renal or hepatic dose adjustment

STOP IF

QTc >500 ms or increase >60 ms from baseline, tendon pain/swelling (discontinue immediately), signs of peripheral neuropathy (burning, numbness, tingling), severe hypersensitivity, jaundice/hepatotoxicity

WATCH

ECG (baseline and if cardiac risk), electrolytes (maintain K+ >4.0, Mg2+ >1.8), tendon pain (especially elderly + steroids), LFTs, glucose (diabetics), CNS effects (elderly)

CDSCO approvedSchedule HATC J01MA14

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 30min · absorption onset
PEAK: 2h · 1-3 h (oral); end of infusion (IV)
t½: 12h · 12 h (supports once-daily dosing)
DURATION: 1d · 24 h (once-daily dosing)

EXCRETION

~45% renal (20% unchanged); ~50% fecal; non-CYP metabolism

route + CYP

INTERACTIONS

12 major

incl. contraindicated

PREGNANCY

FDA PLLR: Avoid during pregnancy. Animal studies showed arthropathy in juvenile animals. Limited human data suggest potential risk. Use only for plague or life-threatening infections where benefit outweighs risk.

FDA category + note

Top interactionssee all 12 →

AmisulprideContraindicatedDatabaseDDInter
CisaprideContraindicatedDatabaseDDInter
Class IaContraindicatedDatabaseKimi deep-research + Cla
DiclofenacSevereTextbook-citedKDT 7e · p949

Available in India

487 branded formulations and 402 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Mechanism

Moxifloxacin is a synthetic fluoroquinolone antibacterial agent that exerts bactericidal activity by inhibiting two essential bacterial enzymes: DNA gyrase (topoisomerase II) and topoisomerase IV. DNA gyrase is responsible for introducing negative supercoils into bacterial DNA during replication and transcription, while topoisomerase IV is essential for partitioning daughter chromosomes during cell division. Inhibition of both enzymes prevents bacterial DNA replication, transcription, and repair, leading to rapid bacterial cell death. Moxifloxacin has enhanced activity against gram-positive organisms (including Streptococcus pneumoniae) compared to earlier fluoroquinolones due to its 8-methoxy substitution.

Indications

Community-acquired pneumonia (CAP) — including multidrug-resistant S. pneumoniaeAcute bacterial sinusitisAcute exacerbation of chronic bronchitisUncomplicated skin and skin structure infectionsComplicated skin and skin structure infectionsComplicated intra-abdominal infectionsPlague (Yersinia pestis) — including pneumonic and septicemic plagueAcute bacterial sinusitis (alternative to beta-lactams in penicillin-allergic patients)

Dosing

Adult: 400 mg PO/IV once daily for all indications. CAP: 7-14 days. Sinusitis: 10 days. Acute bacterial exacerbation of chronic bronchitis: 5 days. Uncomplicated SSSI: 7 days. Complicated SSSI: 7-21 days. Complicated intra-abdominal: 5-14 days. Plague: 10-14 days. IV infusion: over 60 minutes.
Pediatric: Not recommended <18 years (exception: plague — 400 mg PO/IV once daily).
Renal adjustment: No dosage adjustment necessary in any degree of renal impairment, including hemodialysis and CAPD (FDA Avelox label §8.6 — moxifloxacin PK not significantly altered in severe/ESRD).
Hepatic adjustment: No adjustment for mild-moderate hepatic impairment. Use with caution in severe hepatic impairment (Child-Pugh C) — metabolic disturbances may lead to QT prolongation.
Geriatric: No adjustment for age alone. Monitor QT interval, tendon integrity, and CNS effects. Increased risk of tendon rupture (especially with corticosteroids), QT prolongation, and CNS effects.
Max dose: 400 mg/day (no benefit from higher doses; increased toxicity)

Pharmacokinetics

Onset

Rapid bactericidal activity; clinical response typically within 48-72 hours for susceptible infections.

Peak effect

Oral: peak plasma at 1-3 hours (mean ~1.5-2 hours). IV: peak at end of 60-min infusion. Food does not significantly affect absorption.

Duration

24-hour duration supports once-daily dosing. Post-antibiotic effect (PAE) of 2-4 hours against most pathogens.

Half-life

12 ± 1.3 hours (mean elimination t½). Allows once-daily dosing.

Bioavailability

>90% (oral bioavailability approaches IV).

Protein binding

50% (primarily to albumin; concentration-independent).

Metabolism

Approximately 52% metabolized via hepatic glucuronide conjugation (14%) and sulfate conjugation (38%). CYP450 system is NOT involved in moxifloxacin metabolism. This is a key distinction from many other drugs.

Excretion

Fecal: ~25% unchanged + 38% as sulfate conjugate (M1). Renal: ~20% unchanged + 14% as glucuronide conjugate (M2). Overall: approximately 45% renal, 50% fecal.

Contraindications

Hypersensitivity to moxifloxacin or other fluoroquinolones
Known QT prolongation or congenital long QT syndrome
Uncorrected hypokalemia or hypomagnesemia
Concurrent use with other QT-prolonging drugs (Class IA and III antiarrhythmics, certain antipsychotics)
Concurrent use with Class IA antiarrhythmics (quinidine, procainamide) or Class III (amiodarone, sotalol)
History of tendon disorders related to fluoroquinolone use
Myasthenia gravis (may worsen muscle weakness)
Pregnancy and breastfeeding (avoid — cartilage damage in juvenile animals)
Children <18 years (avoid — risk of arthropathy; exception: plague)

Side effects

Common

Nausea, diarrhea, vomitingHeadache, dizzinessAbdominal painInsomniaLiver enzyme elevations (transient)Vaginitis (candida superinfection)

Serious

QT prolongation and torsades de pointes (dose-dependent; contraindicated with other QT drugs)
Tendinitis and tendon rupture (especially >60 years, corticosteroid use, renal transplant) — FDA black box warning for all fluoroquinolones
Peripheral neuropathy (potentially irreversible) — FDA black box warning
Central nervous system effects (seizure threshold lowered, psychosis, hallucinations)
Aortic aneurysm and dissection risk (FDA warning 2018)
Severe hypersensitivity (anaphylaxis, SJS/TEN, DRESS)
Clostridioides difficile-associated diarrhea (CDAD)
Hepatotoxicity (acute liver failure, hepatic necrosis — rare but fatal)
Dysglycemia (hyperglycemia or hypoglycemia, especially in diabetics on insulin/oral hypoglycemics)

Pregnancy & lactation

Pregnancy

Lactation

Excreted in breast milk (infant dose ~2-3% of maternal). Potential risk of arthropathy and QT effects in nursing infant. Avoid during breastfeeding. If necessary, monitor infant for GI upset, rash, and joint symptoms.

Drug interactions

Amisulpride

Contraindicated

Database

Increased risk of Torsades de Pointes (TdP) and other ventricular arrhythmias

Concomitant use is contraindicated. Avoid combination.

Source: DDInter

Cisapride

Contraindicated

Database

Severe QT prolongation and increased risk of Torsades de Pointes

Concomitant use is contraindicated due to high risk of life-threatening arrhythmias.

Source: DDInter

Class Ia

Contraindicated

Database

Additive QT prolongation via hERG potassium channel blockade. Combined use significantly increases risk of torsades de pointes and sudden cardiac death.

Absolute contraindication per FDA label. Choose alternative antibiotic (beta-lactam, azithromycin with caution) or alternative antiarrhythmic if moxifloxacin essential.

Source: Kimi deep-research + Cla

Diclofenac

Severe

Textbook-cited

Enhanced CNS toxicity, seizure risk.

Avoid concurrent use

Source: KDT 7e · p949

Ibuprofen

Severe

Textbook-cited

Enhanced CNS toxicity, seizure risk.

Avoid concurrent use