A popular class of oral antibiotics doubles the risk of experiencing permanent nerve damage, according to new research published in the journal Neurology.

Fluoroquinolones are one of the most-prescribed classes of antibiotics in B.C., often used in cases of respiratory and urinary tract infection, but they have been implicated in a variety of serious side effects.

“An Ontario group found a link with liver disease. We found a link with retinal detachment and kidney disease, and now peripheral neuropathy. These are pretty serious, nasty conditions compared with a more typical antibiotic, which might give you a couple of days of diarrhea,” said lead author Mahyar Etminan, a drug safety researcher at the University of B.C.

The most popular of these drugs, ciprofloxacin, mocifloxacin and levofloxacin, are sold under the trade names Cipro, Avelox and Levaquin.

The U.S. Food and Drug Administration last year ordered a warning be added to the labelling on all fluoroquinolone drugs after receiving anecdotal reports of peripheral neuropathy, which causes muscle weakness, numbness and pain.

Etminan’s group sought to quantify the risk.

“In the past couple of years, there were lots of cases reported to the FDA of peripheral neuropathy, which is a condition in which the patient experiences a pinching in the nerves, eventually interfering with their daily activities,” he said. “Case reports are a powerful tool, but they are at the bottom of the food chain in terms of scientific evidence.”

North Vancouver’s Christina Rey experienced mysterious arthritic pain and weakness after taking ciprofloxacin in 2008, she said in an email interview, but doctors were unable at the time to confirm the cause.

A second course of the drug prescribed earlier this year caused nerve symptoms and pain to return, which are only now starting to ease seven months later, she said. Rey is awaiting a referal to a neurologist, which she hopes will confirm a diagnosis of peripheral neuropathy.

“I am getting better with time, but i’m not sure if I’ll ever be the same as before,” she said. “I have somewhat come to terms with the fact that this is the way things could be from now on.”

The data for Etmanin’s most recent study were gleaned from medical records of about one million American men 45 to 80 years old over a decade. The researchers pulled records of men diagnosed with peripheral neuropathy to determine if they had been prescribed fluoroquinolones. They compared the results with case controls and with men prescribed finasteride, a drug not expected to increase the risk of peripheral neuropathy.

Men who are on fluoroquinolones, especially first-time users, were twice as likely to experience peripheral neuropathy as men who were not.

An earlier study led by Etmanin identified 445 cases of retinal detachment involving oral fluoroquinolone use in a cohort of 989,591 patients from B.C. who visited an ophthalmologist between January 2000 and December 2007.

The finding prompted Health Canada to issue a warning last year in the Canadian Adverse Reaction Newsletter.

The effectiveness of the drugs may tempt physicians to use them, even when alternative treatments are available, explained Etminan.

Fluoroquinolones are a very broad spectrum, covering a lot of bacteria, and they are very readily absorbed, providing the same concentration in the body as intravenous antibiotics, so they may be used to avoid having a patient in hospital, said Etminan.

“Canadian doctors tend to use antibiotics in a more refined way than in the United States. Physicians here are not as likely to prescribe antibiotics. However, physicians need to know not to use these drugs unless they have to,” said Etminan.

rshore@vancouversun.com

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