Calcium and Ofloxacin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ofloxacin
Calcium
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Decreased oral ofloxacin effectiveness
Interaction Deep Dive
Concurrent use of oral ofloxacin and an aluminum, calcium or magnesium containing product may result in decreased serum concentrations of the antibiotic leading to loss of therapeutic efficacy21. If the doses of ofloxacin and aluminum, calcium or magnesium containing products are separated by two hours, the oral bioavailability of ofloxacin is not decreased to a clinically significant extent.
Why it happens (mechanism)
Decreased ofloxacin absorption due to chelation
Literature reports
1 report — tap to read
a) One study reports that magnesium/aluminum hydroxide and calcium carbonate antacids in doses of 5 mL and 15 mL do not interfere in a clinically significant manner with the bioavailability of ofloxacin, provided that an interval of at least two hours separates the administration of these products 2.
Common questions
Can I take Calcium and Ofloxacin together?
Decreased oral ofloxacin effectiveness Always confirm with your pharmacist or prescriber before making any change.
How serious is the Calcium and Ofloxacin interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Calcium or Ofloxacin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there anything you'd monitor while I'm on both?
References (2)
- Monk JP & Campoli-Richards DM: Ofloxacin: a review of its antibacterial activity, pharmacokinetic properties and therapeutic use. Drugs 1987; 33:346-391.
- Flor S, Guay DRP, Opsahl JA, et al: Effects of magnesium-aluminum hydroxide and calcium carbonate antacids on bioavailability of ofloxacin. Antimicrob Agents Chemother 1990; 34:2436-2438. PubMed
Keep reading about Ofloxacin
Keep reading about Calcium
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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