SeriousTiming Sensitive
Calcium
Calcium can reduce oral Moxifloxacin absorption when taken together.
Recommendation: Take moxifloxacin at least 4 hours before or 8 hours after calcium-containing supplements or mineral products.
Moxifloxacin
Prescription ·Strong evidence ·Reviewed May 2026
Moxifloxacin is a fourth-generation fluoroquinolone antibiotic used to treat respiratory tract infections such as community-acquired pneumonia, acute bacterial sinusitis, and acute bacterial exacerbations of chronic bronchitis, as well as certain skin and intra-abdominal infections. It has enhanced activity against Gram-positive organisms and atypical respiratory pathogens compared with earlier fluoroquinolones. Because of serious safety concerns, fluoroquinolones including moxifloxacin are generally reserved for infections without alternative treatment options.
What it's good for
The bottom line
Evidence rating strong. Most-documented uses: community-acquired pneumonia, acute bacterial sinusitis, acute bacterial exacerbation of chronic bronchitis. 3 sources indexed (1995–2016), with 5 interaction records on file.
The science
How it works, mechanistically.
Core mechanism
Moxifloxacin inhibits bacterial DNA replication by targeting two essential type II topoisomerase enzymes: DNA gyrase (topoisomerase II) and topoisomerase IV. By binding to and stabilizing the enzyme-DNA complex, it blocks the religation of cleaved DNA strands, preventing supercoiling regulation and chromosome segregation. This leads to lethal double-strand DNA breaks and is bactericidal. Its balanced dual-target activity against both enzymes reduces the likelihood of single-step resistance mutations relative to older fluoroquinolones.2,1
Class
Fluoroquinolone antibiotic
Dosing
Dosing & protocol.
Common range
400 mg orally or intravenously once daily; typical course 5 to 21 days depending on indication (for example 5 days for COPD exacerbation, 7 to 14 days for community-acquired pneumonia). Ophthalmic solution dosed as 1 drop in the affected eye 2 to 3 times daily.
Recommended form
Oral tablet (400 mg) once daily; intravenous infusion for hospitalized patients; ophthalmic solution for eye infections.
Oral bioavailability is approximately 90 percent and is not significantly affected by food, so it may be taken with or without meals. However, it must be separated from polyvalent cation products. Take moxifloxacin at least 4 hours before or 8 hours after antacids, sucralfate, multivitamins with minerals, and supplements containing magnesium, aluminum, calcium, iron, or zinc, which chelate the drug and markedly reduce absorption.1
Depletions
What it depletes.
Nutrients this medication can lower over time, and what to replace.
Magnesium
MildMoxifloxacin forms insoluble chelate complexes with divalent magnesium cations in the gastrointestinal tract. This is primarily a bidirectional absorption interaction: co-ingestion of magnesium-containing antacids or supplements markedly reduces fluoroquinolone bioavailability, and the chelation can correspondingly impair absorption of magnesium from the same dose. It is an interaction-driven reduction in absorption rather than true systemic depletion of body magnesium stores.
Replace Magnesium (separate administration by at least 2 hours before or 6 hours after moxifloxacin)Monitor Serum magnesium (routine monitoring not generally required for healthy patients on short courses)Onset Only relevant during concurrent dosing; effect is on absorption of the co-ingested dose, not cumulative over the typical 5 to 14 day antibiotic course.
Calcium
MildCalcium ions chelate moxifloxacin in the gut, forming poorly absorbed complexes. The primary clinical consequence is reduced antibiotic bioavailability when taken with calcium supplements, dairy, or calcium-fortified products; absorption of the co-ingested calcium dose may be modestly reduced. This is a co-administration absorption interaction, not a true depletion of body calcium stores.
Replace Calcium (separate administration by at least 2 hours before or 6 hours after moxifloxacin)Monitor Serum calcium (routine monitoring not generally required)Onset Limited to periods of concurrent dosing during the antibiotic course; not a cumulative depletion.
Iron
MildFerrous and ferric iron form stable chelate complexes with the 4-oxo and adjacent carboxyl groups of fluoroquinolones, including moxifloxacin. Co-administration with iron supplements substantially reduces fluoroquinolone absorption and can reduce absorption of the co-ingested iron. This reflects a bidirectional gut chelation interaction during simultaneous dosing rather than systemic iron depletion.
Replace Iron (ferrous sulfate or similar; separate administration by at least 2 hours before or 6 hours after moxifloxacin)Monitor Serum ferritin and hemoglobin (only if pre-existing iron deficiency is being treated)Onset Relevant only when iron and moxifloxacin are taken together; no cumulative systemic depletion expected over a standard course.
Zinc
MildZinc, a divalent cation, chelates moxifloxacin in the gastrointestinal tract, forming poorly soluble complexes. As with other multivalent minerals, the dominant effect is reduced fluoroquinolone bioavailability on concurrent dosing, with possible modest reduction in absorption of the co-ingested zinc. This is a co-administration absorption interaction, not depletion of body zinc stores.
Replace Zinc (separate administration by at least 2 hours before or 6 hours after moxifloxacin)Monitor Plasma zinc (routine monitoring not generally required)Onset Limited to concurrent dosing periods; no meaningful cumulative depletion over a typical course.
Safety
Full safety detail.
Side effects
- Nausea, diarrhea, and dyspepsia
- Headache and dizziness
- QT interval prolongation (dose-dependent)
- Tendinitis and tendon rupture, including the Achilles tendon
- Peripheral neuropathy (may be irreversible)
- Central nervous system effects (confusion, insomnia, anxiety, seizures)
- Photosensitivity
- Clostridioides difficile-associated diarrhea
- Dysglycemia (hypoglycemia and hyperglycemia)
- Aortic aneurysm and dissection (rare)
Contraindications
- Known hypersensitivity to moxifloxacin or other fluoroquinolones1,2
- History of tendon disorders or tendon rupture associated with fluoroquinolone use2
- Myasthenia gravis (may exacerbate muscle weakness)
- Concurrent use with Class IA or Class III antiarrhythmics or other QT-prolonging drugs (caution)
- Known prolongation of the QT interval, uncorrected hypokalemia, or significant bradycardia
Interactions
Interaction records.
SeriousTiming Sensitive
Iron
Iron can reduce oral Moxifloxacin absorption when taken together.
Recommendation: Take moxifloxacin at least 4 hours before or 8 hours after iron supplements.
SeriousTiming Sensitive
Magnesium Glycinate
Magnesium Glycinate can reduce oral Moxifloxacin absorption when taken together.
Recommendation: Take moxifloxacin at least 4 hours before or 8 hours after magnesium-containing supplements, antacids, or mineral products.
SeriousTiming Sensitive
Zinc
Zinc can reduce oral Moxifloxacin absorption when taken together.
Recommendation: Take moxifloxacin at least 4 hours before or 8 hours after zinc supplements or multivitamins with zinc.
ModerateCaution
Berberine
Moxifloxacin prolongs the QT interval, and combining it with berberine adds theoretical additive risk. Berberine inhibits the hERG potassium channel and has been associated with QT prolongation, and it can also lower blood glucose, which is relevant because fluoroquinolones themselves can cause dysglycemia.
Recommendation: Use caution when combining berberine with moxifloxacin, particularly in patients with cardiac risk factors, electrolyte abnormalities, or other QT-prolonging agents. Consider pausing berberine during the antibiotic course and monitor glucose in diabetic patients.
Sources
Sources, by evidence tier.
Numbered references. Citations throughout the page link here.
Reviews & position papers
1- 1Pharmacokinetic drug interactions of fluoroquinolones with multivalent cation-containing productsNeeds reviewNo linkLomaestro BM, Bailie GR · Clinical Pharmacokinetics · 1995
Co-administration with magnesium, aluminum, calcium, iron, or zinc forms insoluble chelates that markedly decrease fluoroquinolone bioavailability, requiring dose separation.
Reference material
2- 2Avelox (moxifloxacin hydrochloride) Prescribing InformationNeeds reviewNo linkBayer HealthCare Pharmaceuticals; U.S. Food and Drug Administration · FDA Label · 2016
400 mg once-daily dosing is approved for community-acquired pneumonia, acute bacterial sinusitis, COPD exacerbations, and skin and intra-abdominal infections, with black box warnings for tendon, nerve, and CNS effects.
- 3FDA Drug Safety Communication: serious side effects with fluoroquinolone antibacterial drugsNeeds reviewNo linkU.S. Food and Drug Administration · FDA Drug Safety Communication · 2016
FDA advises that systemic fluoroquinolones be reserved for patients with no alternative treatment options for acute sinusitis, acute bronchitis, and uncomplicated UTI due to the risk of disabling and irreversible adverse events.
Keep exploring
Deep dives & adjacent profiles.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
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