KE is a 72-year-old female residing in a long-term care facility. She was recently started on ciprofloxacin 500 mg PO BID for a complicated urinary tract infection caused by E. coli. Over the past week, nursing staff noticed she continued to spike fevers, complain of dysuria, and her urine cultures remained positive despite being on ciprofloxacin. In this case, we will describe how ciprofloxacin with iron can lead to treatment failure. This is also a great nugget that may show up on your boards!
Full Medication List
- Ciprofloxacin 500 mg PO BID (new, for UTI)
- Ferrous sulfate 325 mg PO BID (iron-deficiency anemia)
- Lisinopril 20 mg PO daily (hypertension)
- Metoprolol succinate 50 mg PO daily (hypertension, rate control)
- Atorvastatin 40 mg PO nightly (hyperlipidemia)
- Furosemide 20 mg PO daily (CHF)
- Aspirin 81 mg PO daily (CAD prevention)
- Omeprazole 20 mg PO daily (GERD)
- Levothyroxine 75 mcg PO daily (hypothyroidism)
- Sertraline 50 mg PO daily (depression)
- Acetaminophen 650 mg PO q6h PRN pain
- Calcium carbonate/Vitamin D 500 mg/200 IU PO BID (osteoporosis prevention)
A medication review revealed that she takes ferrous sulfate 325 mg PO BID for iron-deficiency anemia. The iron is scheduled at 0800 and 2000, exactly the same times ciprofloxacin is given. In addition, this patient is also taking calcium carbonate. With both of these medications on board and likely being given at the same time as ciprofloxacin, this would drastically reduce the absorption of the antibiotic. I would anticipate that with two medications on board that could both bind ciprofloxacin, concentrations would be reduced at least 50% or more.
Ciprofloxacin should be given at least 2 hours before or 6 hours after iron and calcium. Oral absorption is fairly rapid so 2 hours should be an adequate amount of time to get full absorption of the ciprofloxacin. The other option would be to hold the iron and calcium for the course of treatment. Holding these medications for 5-7 days likely wouldn’t be catastrophic for the patient in most situations.
This also presents a unique excuse to review the continued need for iron and calcium supplements. Most patients will continue to need these supplements, but as I’ve seen so many times in my career, supplements get continued indefinitely despite adequate levels and replacement.
Whenever you see an order for an oral quinolone, you must review the entire medication list and ensure that the patient is not taking supplements that will interfere with absorption. This case presents a perfect example of how ciprofloxacin with iron can cause treatment failure.
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