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Common antibiotic can cause potentially fatal blood sugar abnormalities


A new study from the Institute for Clinical Evaluative Sciences (ICES) shows that the antibiotic gatifloxacin is associated with an increased risk of potentially life-threatening hypoglycemia (low blood sugar levels) and hyperglycemia (high blood sugar levels) compared to other antibiotics in the same drug class.

“Gatifloxacin is one member of a class of antibiotics called fluoroquinolones, which are currently the most prescribed antibiotics in North America,” said the study’s lead author and ICES research fellow Dr. Laura Park-Wyllie.

“However, in recent years, several other fluoroquinolones have been withdrawn or restricted because of serious adverse events. Several reports suggest that gatifloxacin is particularly prone to influence blood glucose levels.”

To provide further perspective on this issue, investigators studied the association between antibiotic use and subsequent hospital visits for high and low blood sugar levels, in Ontario residents aged 66 years and older between April 2002 and March 2004.

The results showed that patients treated for low blood sugar levels were over four times more likely to have received gatifloxacin in the preceding 30 days, compared to other common antibiotics. Patients hospitalized with high blood sugar levels were almost 17 times more likely to have recently been treated with gatifloxacin in the preceding 30 days than with other antibiotics. The risk of glucose abnormalities was not restricted to patients with diabetes, who tend to have more blood sugar concerns than the general population.

In contrast, no major increased risk of low or high blood sugar levels was seen with any other fluoroquinolone.

“It is important to make sure that patients taking gatifloxacin recognize the symptoms of high and low blood sugar levels so that they can seek medical attention immediately,” said study co-author and ICES scientist Dr. David Juurlink.

Symptoms of low blood sugar include confusion, lightheadedness, shakiness, perspiration, palpitations, and trouble speaking, while the symptoms of high blood sugar include excessive urination and thirst, confusion, and nausea. However, symptoms can vary dramatically from person to person, and some patients may have dangerous blood sugar levels but few symptoms.

“Physicians and pharmacists should also be aware of the increased risk of potentially life-threatening blood sugar abnormalities with gatifloxacin therapy. Clinicians should carefully weigh the risks of gatifloxacin, particularly because many other antibiotics are available that have little or no risk of dangerous effects on blood sugar levels,” said Dr. Juurlink.

The study, “Outpatient gatifloxacin therapy and dysglycemia in older adults”, is available as an early online release article in the New England Journal of Medicine.

Author affiliations: ICES (Drs. Park-Wyllie, Juurlink, Shah, Stukel, and Mamdani, and Mr. Kopp); Centre for Research on Inner City Health, Department of Family and Community Medicine, St. Michael’s Hospital (Dr. Park-Wyllie); Department of Medicine and the Clinical Epidemiology Unit, Sunnybrook and Women’s College Health Sciences Centre (Drs. Juurlink, Shah, and Stukel); Department of Microbiology, University Health Network/Mount Sinai Hospital (Dr. Low); Departments of Medicine (Drs. Juurlink and Shah), Microbiology (Dr. Low), Pediatrics (Dr. Juurlink), and Pharmacy (Drs. Mamdani and Dresser), and Health Policy, Management and Evaluation (Drs. Juurlink, Mamdani, and Stukel), University of Toronto; Departments of Pharmacy, Toronto East General Hospital (Dr. Stumpo), and Mount Sinai Hospital (Dr. Dresser).

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of healthcare issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting healthcare needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.


  • Julie Dowdie
  • Media Relations Officer, ICES
  • (416) 480-4780 or cell (416) 432-8143


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