Common antibiotic linked to potentially fatal blood-sugar changes: study

http://news.yahoo.com/s/cpress/20060301/ca_pr_on_he/health_antibiotic_worries_2

SHERYL UBELACKERWed Mar 1, 6:47 PM ET
TORONTO (CP) - One of the most widely prescribed antibiotics in North America appears to dramatically boost the risk of potentially life-threatening blood sugar abnormalities, a large-scale study by Canadian researchers has found.
The study found that the antibiotic gatifloxacin, sold under the brand name Tequin by manufacturer Bristol-Myers Squibb, is associated with an increased danger of both low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia), when compared with other antibiotics.
"What we found was that people taking gatifloxacin had more than a fourfold increase in the risk of being treated in hospital for low blood sugar than people who were on other antibiotics," study co-author Dr. David Juurlink said Wednesday.
"And the people on gatifloxacin had almost 17 times more risk of developing high blood sugar," said Juurlink, a senior researcher at the Institute for Clinical Evaluative Sciences (ICES) in Toronto.
The research, released online Wednesday by the New England Journal of Medicine, involved patients over age 65 admitted to hospital in Ontario. While younger patients were not part of the study, Juurlink believes they, too, could be adversely affected by the drug.
He warned that both low and high blood sugar, or glucose, can be fatal, although plunging levels can cause death more quickly.
It's unusual for a drug to have two opposing effects, but it's believed Tequin may interfere with regulation of insulin secretion from the pancreas, which controls blood sugar levels. It is not known why some patients on the drug get low blood sugar, while others end up with an elevated level.
Symptoms of low blood sugar include sweating, shakiness, confusion, light-headedness, a racing heart beat and trouble speaking. As the levels drop further, a person may experience seizures, coma and eventually death.
The hallmarks of high blood sugar include excessive urination and thirst, confusion, and nausea. The condition can escalate to the point of coma and death.
There have been 14 deaths in Canada potentially linked to low or high blood sugar among users of Tequin since the drug was approved in 2001. The cases are still being assessed and no link between the drug and the deaths has been established. As of December 31, Health Canada had also received 169 reports of low blood sugar and 109 reports of high blood sugar possibly related to the drug.
However, some people with abnormal blood sugar may experience no symptoms at all.
If someone taking Tequin develops any of these symptoms, "they need to seek medical attention urgently," said Juurlink. Even those without symptoms taking the drug should discuss with their physicians whether their medication should be changed, he said.
Previous reports about the broad -spectrum antibiotic - commonly prescribed for bacterial infections of the lungs, sinuses and urinary tract - suggested it caused blood sugar abnormalities in diabetics, who already have problems maintaining control of blood glucose.
But the ICES study found that the drug also adversely affected patients without diabetes," said Juurlink.
"And this is important because the recent warnings that have come forth from regulators (Health Canada and the U.S. Federal Drug Administration) and the company really have stressed the avoidance of this drug in patients with diabetes.
"Our result simply is that this is a problem that can affect people who do not have diabetes, as well."
Health Canada, which recently issued two warnings about possible adverse effects for diabetics taking gatifloxacin, plans to update safety information on the drug's product labelling and is considering whether that should include a "black box" warning, spokeswoman Jirina Vlk said from Ottawa. A black box warning is used when a drug is potentially lethal.
"The department is enhancing the warnings for non-diabetic patients as well," she said. "The issue here is to try to restrict the use to mitigate the risk."
Marc Osborne, a spokesman for Bristol-Myers Squibb in Canada, said the company notified Health Canada in December about new safety information on Tequin and informed Canadian doctors and pharmacists through special letters.
Whether newer warnings would be issued for non-diabetics in light of the ICES study's findings is something that would be decided in conjunction with Health Canada, Osborne said from Montreal.
"Tequin is generally well-tolerated in appropriate patients," he said.
Gatifloxacin belongs to a class of antibiotics called fluoroquinolones, the most prescribed antibiotics in North America. While one other drug in the class, called levofloxacin, appeared to slightly increase the risk of low blood sugar, Juurlink said the adverse effects on blood glucose are not a "class effect."
Still, he advised doctors to think twice before prescribing Tequin.
"I will never prescribe this drug," he said. "These side-effects can kill people. They are relatively common as side-effects go. They are unpredictable and we've got plenty of alternative agents out there that we could use instead."
Commenting on the study in an editorial, Dr. Gerry Gurwitz of the Meyers Primary Care Institute in Worcester, Mass., said previous FDA and Health Canada decisions not to put black box warnings on Tequin's labelling "probably warrants reconsideration" in view of the Canadian findings.
"Gatifloxacin now takes its place among an ever-growing list of medications that have been associated with very serious adverse effects. The most immediate question is what should be done with gatifloxacin?" writes Gurwitz, an expert in geriatric medicine.
"It seems clear that the drug's place among broad-spectrum antibiotics available for out-patient use is tenuous at best. For every approved indication for gatifloxacin, there are safer, equally effective and less costly alternatives."