Misuse of Fluoroquinolones May Be Causing Drug-Resistant Tuberculosis

-DG News

08/11/2009 - Use of a fluoroquinolone may be undercutting its utility as a first-line defense against drug-resistant tuberculosis (TB), according to a study published in the August 15 issue of the American Journal of Respiratory and Critical Care Medicine.

"While fluoroquinolone resistance in TB strains has been reported since the mid 1990's, to our knowledge no one had investigated the direct causes of it," said Rose A. Devasia, MD, Vanderbilt University, Nashville, Tennessee. "We wanted to determine whether and to what extent clinical practices were having an effect of creating that resistance."

To investigate the causes of the small but growing proportion of fluoroquinolone-resistant TB cases, Dr. Devasia and colleagues performed a retrospective case-control study using data from the Tennessee Department of Health.

They analysed the records of every newly diagnosed patient with culture-confirmed TB who was also enrolled in Tennessee's Medicaid program, TennCare between January 2002 and December 2006. Using the TennCare pharmacy database, they were able to obtain information on the patients' use of fluoroquinolone for the 12 months prior to their TB diagnosis. They used M. tuberculosis isolates taken from each patient to test for fluoroquinolone resistance in each case.

After excluding those who were not enrolled in TennCare or whose culture were either unavailable or unusable, the researchers analysed data for 640 patients. Age, race, and other demographic factors were not significantly associated with resistance, but when researchers further analysed the data they found a linear association between previous fluoroquinolone exposure and fluoroquinolone resistance.

Overall, patients who had used fluoroquinolones within 12 months of diagnosis were almost 5 times as likely to have a fluoroquinolone-resistant strain of TB than those who had not used fluoroquinolones, and there was a linear association between length of fluoroquinolone use and fluoroquinolone resistance.

"Patients who had undergone shorter treatment (<10 days) had a relatively low rate of resistance of only 1.6%," said Dr. Devasia. "[But] for every additional 10 days of fluoroquinolone use, we found that patients had a 50% increase in the likelihood of having resistant TB. Of the116 people who had taken fluoroquinolones, 13% had fluorquinolone-resistant TB."

Interestingly, Devasia and colleagues found that fluoroquinolone resistance was highest among those who had undergone treatment more than 60 days prior to TB diagnosis. "Exposure to fluoroquinolones early in the course of disease may select for and allow a fluoroquinolone-resistant strain to predominate," explained Dr. Devasia.

"These findings underscore the importance of considering TB in people with symptoms consistent with it and to limit the use of fluoroquinolone in those patients until TB can be definitively ruled out and that repeated courses of fluoroquinolones for the same clinical symptoms may be an indication that TB is the real problem," said Dr. Devasia.

If you or a loved one have experienced serious side effects or injury as a result of Fluoroquinolone antibiotics such as tendonitis, torn ligament, or ruptured tendons, you may be entitled to compensation. Contact one of our Fluoroquinolone lawyers today for more information regarding your legal rights. For more information about a potential Fluoroquinolone lawsuit, or Fluoroquinolone side effects, fill out our free case evaluation form or call the toll-free number listed below.