Quinolone interactions with divalent or trivalent cations: have you checked the medication administration report lately?

To the Editor: Because of the significant interaction between quinolone antimicrobial agents and several divalent or trivalent cations, (1-4) we recently changed our computer-generated nurses' medication administration report (MAR) to schedule quinolones automatically 2 hours before products with these cations. Although we had previously included a preprinted note to the nurses on the MAR that administration of quinolones should be spaced 2 hours before these cations, it was not effective in changing nurses' behavior. Consequently, after receiving Pharmacy & Therapeutics Committee approval to have appropriate scheduling automatically, we thought that the problem was solved. For example, once-daily levofloxacin was scheduled in the computer at 6 AM by default; therefore, the medication would be administered at the time printed on the MAR.

Much to our dismay, we recently noted that a night shift nurse withheld the 6:00 AM dose until 8:00 AM to avoid waking the patient (thus ensuring coadministration with a scheduled magnesium product and breakfast, which is usually high in calcium). We wonder how many other hospitals have developed similar solutions to this problem but forgot to look at the MAR. Upon this discovery, we conducted a nursing inservice program further explaining the highly significant nature of these interactions leg, 85% reduction in bioavailability of ciprofloxacin with 1he same administration time as 30-ml magnesium-aluminum antacid, (2) 90% reduction in bioavailability of ciprofloxacin with sucralfate (3)).

Our point obviously has much larger implications than this one drug interaction. Despite advancing technology that continually facilitates improved patient care, health care professionals still ultimately must scrutinize the MAR to determine exactly when and if medications have been administered. We hasten to add that we admire and respect our nurse colleagues. They are absolutely essential members of the health care team, mad most of our nurses are highly skilled and conscientious. We acknowledge that the worsening nurse shortage adds to this dilemma, so that doses are not always administered as scheduled. (5) If each member of the health care team continues to work with colleagues and shares clinically relevant information, patient care will improve, including optimal administration times to avoid potential sub-therapeutic response.

Amy M. Redmond, PharmD

Clinical Pharmacy Resident

John M. Norwood, MD

Division of Infectious Diseases

Department of Medicine

Naseem Amarshi, PharmD

Timothy Self, PharmD

College of Pharmacy 

University of Tennessee Health Science Center 

Memphis, TN

References

(1.) Hooper DC. Quinolones, in Mandell GL, Bemlett JE, Dolin R (eds): Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. Philadelphia, Churchill Livingstone, 2000, vol 1, ed 5, pp 404-422.

(2.) Nix DE, Watson WA, Lener ME, et al. Effects of aluminum and magnesium antacids and ranitidine on the absorption of ciprofloxacin. Clin Pharmacol Ther 1989;46:700-705.

(3.) Garrelts JC, Godley PJ, Peterie JD, et al. Sucralfate significantly reduces ciprofloxacin concentrations ill serum. Anfimicrob Agents Chemother 1990;34:931-933.

(4.) Kara M, Hasinoff BB, McKay DW, et al. Clinical and chemical interactions between iron preparations and ciprofloxacin. Br J Clin Pharmacol 1991;31:257-261.

(5.) Aiken LH. Clarke SP, Sloane DM, et al. Hospital nurse staffing and patient mortality, nurse burnout, and job dissatisfaction. JAMA 2002;288:1987-1993.