Antibiotic Failure: Iron and Levaquin Drug Interaction – Case Study

44 year old male with a history of respiratory issues.  Recently diagnosed at the clinic with pneumonia.  Levaquin (oral) was initiated for a 10  day period.

Current medication list includes:

  • Advair 250/50 twice daily
  • Albuterol as needed
  • Hydrochlorothiazide 25 mg daily
  • Ferrous Sulfate 325 mg twice daily
  • Prilosec 20 mg daily

Day 7 of 10 for the Levaquin course and the patient is not improving.  He presents to the clinic for reassessment of pneumonia and requests a different medication.  A Zpak is prescribed and within 3-5 days the patient begins feeling much better with a full resolution of the pneumonia following treatment with azithromycin.

So, what happened?  We can only speculate, but I’ve got three major points that I think could’ve been the problem.

1.  Assessment of adherence is critical with antibiotics and any medication for that matter – that is where I would start.

2.  Resistance to antibiotics is a significant problem and could be at play here.

3.  I’ve seen this happen several times, and I think it might lead to failure more often then we realize especially with quinolone antibiotics.  The iron and Levaquin drug interaction is well known, but does slip through the cracks, especially with polypharmacy complicating things.  Iron can significantly block absorption of Levaquin leading to low concentrations in the blood and potentially low enough to cause failure of treatment.  Again only speculation, but this is an interaction you should be aware of and frequently assess for use of products with iron, calcium, and magnesium which can all bind up Quinolones.

Here’s another Levaquin interaction you should know!

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  1. Brian J. Catton, PharmD

    Good post about Levaquin and the fluoroquinolones. This is why I make a concerted effort to counsel patients to take the antibiotic 2 hours before or after their medications and/or when they have something to eat.

    In the words of Brian Regan, LAY OFF THE DAIRY!… GOODBYE HAPPINESS!

  2. Reki Baboo

    This is only a problem with PO levaquin. IV would not be a problem since bioavailability is 100%. Absorption is not an issue with IV meds.

  3. Lanye

    Yes, this is also a common issue I see in long-term care facilities during medication passes, fluoroquinolones being given with supplements – proper time of administration common recommendation regarding antibiotic therapy.

  4. Sheshagiri Gandasi

    You might be correct in the anlysis of the problem , but the information is incomplete in that it doesn’t inform about the dosage form or the route of administration. The accopanying Photo indicates an IV route, for Levofloxacin, but the Ferrous Sulphate appears to be oral. In that case the absorption of IV Levofloxacin is 100% with no chance of binding with Iron before it is available to exert its antibiotic actvity. Aclarification regarding this would dispel all doubts

    • chri1599

      Good point, thanks for the comment! I will clarify that. – Eric

      • Sheshagiri Gandasi

        Three weeks on, and I am still awaiting anxiously for the clarification you promised, Chris. May be you are too busy.

        • Eric Christianson

          I apologize, I should’ve have updated you. I did change it in the article, just forgot to send you a message. Take care, Eric

          • Sheshagiri Gandasi

            Thanks Chris, for the kind clarification. Now, I know.


  1. Doxycycline Pharmacology and Clinical Pearls - Med Ed 101 - […] Supplements like iron, calcium, and magnesium can impair absorption the absorption of doxycycline and other tetracycline antibiotics.  These interactions…
  2. Clopidogrel Failure: Why Did I Have Another Heart Attack? - Med Ed 101 - […] Here’s another case that might interest you of antibiotic failure due to a drug interaction. […]

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Written By Eric Christianson

December 14, 2014

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