A new study shows that misuse of a class of antibiotic drugs called
fluoroquinolones is creating drug-resistant strains of tuberculosis, or
TB, a bacterial respiratory disease that the World Health Organization
says kills two million people worldwide each year. The finding dims
hopes that the drug could be used more widely to treat this deadly
disease.
Overreliance on certain antibiotics
Although
TB is curable, treatment requires at least six months of continuous
therapy using several drugs at once. Researchers have been hopeful that
fluoroquinolones could help change that.
But Rose Devasia, an
infectious disease researcher at Vanderbilt University, says the effectiveness of these
safe, easy-to-take drugs has led to widespread overprescribing for a
range of illnesses, sometimes even before it's known what kind of
infection is being treated.
That, says Devasia, can cause
problems when patients actually have tuberculosis. "Say they go to an
emergency room and they have a cough. The physician thinks, 'Oh, it's
probably pneumonia. I'm going to give him a fluoroquinolone.' The
fluoroquinolone partially [treats] the TB. He feels good for about 10,
12, 13 days, but then the cough comes back," she says.
"So he
goes to another physician or he goes back to another emergency room. He
says, 'I've got this cough.' He gets another course of
fluoroquinolones." Devasia says each time a patient with undiagnosed
tuberculosis is treated for the wrong disease using fluoroquinolones,
it increases the risk that he'll develop fluoroquinolone-resistant TB.
Researching the connection between TB and fluoroquinolones
In
a study published in the American Journal of Respiratory and Critical Care
Medicine, Devasia and her colleagues found that nearly one in five
tuberculosis patients had received fluoroquinolones in the year before
they were diagnosed with TB.
A typical course of
fluoroquinolones is about 10 days. For every additional ten days a
patient took the medications, the odds of developing
fluoroquinolone-resistant TB increased by 50 percent.
In many
developing-world pharmacies, fluoroquinolones are easily available
without a prescription, under names such as Cipro and Levaquin, and
they're used to treat everything from diarrhea to pneumonia.
Devasia
says the results of her study make her hesitant to support using
fluoroquinolones as the first choice against TB. She prefers to save
them for cases when the usual first-line drugs fail.
Reevaluating recommendations
Neel
Ghandi, assistant professor at the Albert Einstein College of Medicine
says, "To some degree, to me the message from this article is that we
need to reconsider how we use fluoroquinolones generally."
He
says when you're not sure why a patient is sick, fluoroquinolones may
be fairly safe and easy to use. But, he says, emerging drug resistance
demonstrates the consequences of misuse. Ghandi says there are very few
effective drugs to treat TB, and it will be at least five to 10 years
before any new drugs are available.
"The fluoroquinolones are
our next hope in terms of really modifying TB care," says Ghandi. "And
when you see resistance emerge the way it has in this article, I think
it is a good reason to pause and say, 'Perhaps we need to re-evaluate
how we're using these medications.'"
Ghandi notes that the study
was done in the United States, where better tools are available to
diagnose diseases. He says many more resources need to be invested in
diagnostics capabilities in the developing world so doctors there can
identify and treat patients for the right disease and save
fluoroquinolones for when they're truly needed. Study author Devasia is
working on a way to cut the time it takes to diagnose resistant TB from
weeks to hours.
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