The short answer
Oral iron can substantially reduce absorption of moxifloxacin tablets. Use the current product instruction: moxifloxacin at least 4 hours before or 8 hours after the iron product. The direct study tested ferrous sulfate; it did not establish the exact effect of every iron preparation.
What this answer covers
Oral moxifloxacin hydrochloride tablets and oral iron products, with direct study evidence for ferrous sulfate. Intravenous iron and ophthalmic moxifloxacin are not assessed by this interaction.
- Supplement or preparation
- Iron
- Medication ingredient
- moxifloxacin
What did the ferrous sulfate study find?
In a randomized crossover study of 12 healthy men, ferrous sulfate providing 100 mg elemental iron was given with moxifloxacin 400 mg and again the next day. Relative antibiotic bioavailability fell to 61% and the peak concentration ratio to 41% of control. This demonstrates reduced exposure under that regimen, not the probability that any particular infection will fail to improve.
Which timing instruction should I follow?
Take moxifloxacin at least 4 hours before iron, or at least 8 hours after iron. The tablet’s current administration section provides that direction. If iron comes first, waiting only four hours would not meet it. The small original trial tested simultaneous dosing; it does not independently prove the best interval for each iron formulation.
Does iron in a prenatal or multivitamin count?
Iron can be present alongside zinc and other ingredients in combined supplements. The tablet label includes iron-containing products, so inspect the full panel even if the front of the bottle says multivitamin. The measured result for ferrous sulfate should not be transferred as an exact percentage to every newer iron complex or lower-dose blend.
What if iron was prescribed for a deficiency?
Ask the pharmacist to make a schedule that preserves both treatments. A spacing issue does not mean the reason for iron treatment has disappeared. If you already took the products close together, seek individual advice; neither the label nor the trial supplies a formula for taking extra moxifloxacin to replace the amount that might not have been absorbed.
Evidence and practical considerations
Absorption & effectiveness
Oral iron can substantially reduce absorption of moxifloxacin tablets. Use the current product instruction: moxifloxacin at least 4 hours before or 8 hours after the iron product. The direct study tested ferrous sulfate; it did not establish the exact effect of every iron preparation.
- Exact scope
- oral iron, with direct trial evidence for ferrous sulfate providing 100 mg elemental iron with oral moxifloxacin hydrochloride tablets with strengths expressed as moxifloxacin
- Medication form and route
- oral
- Timing or duration
- Single moxifloxacin dose with iron given concurrently and again after 24 hours.
What remains uncertain
- Twelve healthy men, single antibiotic dose and one iron preparation; the numeric interval comes from current labeling rather than a directly inspected spacing trial.
Factors that may matter: exact salt and dose; order and interval between doses; other mineral ingredients; oral tablet versus other routes.
Read the supporting source summaries
Source 1: regulatory product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: Patients prescribed oral moxifloxacin tablets.
Directs moxifloxacin at least 4 hours before or 8 hours after the listed products. Reports lower exposure with aluminum/magnesium antacid and ferrous sulfate. Tablet directions also explicitly name zinc.
How this applies: An explicit hydrochloride-to-active-moiety equivalence supports a bounded oral tablet article for parent RxCUI 139462, without merging salt identities or applying gut-absorption findings to injection or ophthalmic use. Article-specific counterparty: oral iron, with direct trial evidence for ferrous sulfate providing 100 mg elemental iron.
Does not provide a zinc-only clinical trial, or equivalent effect sizes for all magnesium or aluminum salts. Contains no proof that a generic four-hour interval works in both directions.
Source 2: human pharmacokinetic study
pubmed.ncbi.nlm.nih.gov · Source check Sep 10, 2026
Population: Twelve healthy men aged 19-41 years in a randomized, nonblinded two-period crossover study.
Relative antibiotic bioavailability was 61% (90% CI 54-69%); peak concentration ratio was 41% (90% CI 34-49%). Peak timing was delayed.
How this applies: Direct for oral ferrous sulfate and moxifloxacin; current regulatory-label interval supplies practical timing beyond the concurrent-dose trial. Article-specific counterparty: oral iron, with direct trial evidence for ferrous sulfate providing 100 mg elemental iron.
Single antibiotic dose in healthy men; did not test every iron salt, a spacing schedule, or infection outcomes. Study participants and authorship from sponsor research should be considered. Full clinical paper was not assessed; inspected source is the original author abstract.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Original product guidance and clinical studies checked; complete private article drafted with exact preparation limits and claim dispositions. | |
| Research summary published |
Article revision: 2a9a50fd5905cd98
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.