Levofloxacin
Broad-spectrum respiratory fluoroquinolone active against gram-negative, atypical, and some gram-positive (including S. pneumoniae) pathogens. Near-complete oral bioavailability (~99%) allows IV-to-PO transition without dose change. Typical 500-750 mg once daily. FDA black-box warnings for tendinopathy/rupture, peripheral neuropathy, CNS effects, and exacerbation of myasthenia gravis.
Projected serum levels — 500 mg, once daily
Maintenance schedule: 500 mg once daily (oral).
Modeled steady state after ~1 days: peak ≈ 331 mg, trough ≈ 0.82 mg body load. Population-based estimate over 15 days for a 500 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- Antibiotic
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 6.9 h
- Common dose
- 500 mg
- Suggested maximum
- 750 mg/day
- Reference dose range
- 250–750 mg (single dose)
- Suggested cadence
- once daily
- Validated against
- 500 mg oral — Cmax 5.7 mg/L at 1.3 h
Documented interactions
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warning
Diltiazem + Levofloxacin
Diltiazem and Levofloxacin both prolong cardiac repolarisation (l type calcium channel and herg). Combined risk of QTc prolongation and torsades de pointes.
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warning
Felodipine (Plendil) + Levofloxacin
Felodipine (Plendil) and Levofloxacin both prolong cardiac repolarisation (l type calcium channel and herg). Combined risk of QTc prolongation and torsades de pointes.
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warning
Kava (Kavalactones) + Levofloxacin
Kava (Kavalactones) and Levofloxacin both prolong cardiac repolarisation (l type calcium channel and herg). Combined risk of QTc prolongation and torsades de pointes.
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warning
Nifedipine (Procardia / Adalat) + Levofloxacin
Levofloxacin and Nifedipine (Procardia / Adalat) both prolong cardiac repolarisation (l type calcium channel and herg). Combined risk of QTc prolongation and torsades de pointes.
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warning
Oxcarbazepine (Trileptal) + Levofloxacin
Levofloxacin and Oxcarbazepine (Trileptal) both prolong cardiac repolarisation (l type calcium channel and herg). Combined risk of QTc prolongation and torsades de pointes.
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caution
Azithromycin (Z-Pack / Zithromax) + Levofloxacin
Azithromycin (Z-Pack / Zithromax) and Levofloxacin both prolong cardiac repolarisation (herg). Combined risk of QTc prolongation and torsades de pointes.
Serum checks 41 modeled interaction pairings for levofloxacin across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.
Research behind this entry
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The pharmacokinetics of levofloxacin in healthy volunteers and patients
Foundational PK review establishing levofloxacin's 99% oral bioavailability, 6-8 hour half-life, predominantly renal elimination, and linear kinetics supporting once-daily dosing up to 750 mg.
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Fluoroquinolones and the risk for ruptures of the Achilles tendon in elderly patients
Population case-control study of 1841 Achilles tendon ruptures showing fluoroquinolone exposure conferred a 3-fold increased risk, particularly in elderly and corticosteroid users, evidence underlying the FDA black-box…
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A Double-Blind, Randomized Comparison of Levofloxacin 750 mg Once-Daily for Five Days with Ciprofloxacin 400/500 mg Twice-Daily for 10 Days for the Treatment of Complicated Urinary Tract Infections and Acute Pyelonephritis
RCT of 1109 patients with cUTI/pyelonephritis demonstrated levofloxacin 750 mg x 5 days was non-inferior to ciprofloxacin 400/500 mg BID x 10 days, supporting high-dose short-course strategy.
3 published studies referenced in the app, each with a plain-language summary.