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Antibiotics May Ease Alzheimer's Symptoms

But therapy 'not ready for prime time,' researcher says

THURSDAY, Oct. 9, 2003 (HealthDayNews) -- Two common antibiotics, when taken together, may improve the symptoms of Alzheimer's disease, claims a new Canadian study.

But the Alzheimer's Association urges caution about the results, and even the lead researcher says the concept needs more study before it is routinely recommended.

"It's not ready for prime time," says Dr. Mark B. Loeb, an associate professor in the department of pathology and molecular medicine at McMaster University in Hamilton, Ontario. He is to present his findings on Oct. 11 at the Infectious Diseases Society of America's annual meeting in San Diego.

An estimated 4.5 million Americans have Alzheimer's disease, according to estimates from the Alzheimer's Association. Up to 16 million are projected to have it by 2050, the group says, unless an effective cure or treatment is found.

Loeb and his colleagues evaluated 101 patients with "probable" Alzheimer's and mild-to-moderate dementia. The team assigned them randomly to a group that received 200 milligrams of the antibiotic doxycycline and 300 milligrams of rifampin daily for three months.

They evaluated them before the study using a standard Alzheimer's test to determine mental functioning, and then repeated the test to the 43 remaining in the antibiotic group and the 39 remaining in the placebo group after six months.

The scores of those in the dummy pill group declined on average by 2.75 more points than those in the treated group on a 70-point scale. At 12 months there was still a difference in function, although it was not a significant one.

"The magnitude of the difference was similar to the effects seen with therapy with cholinesterase inhibitors," Loeb says. This class of drugs, approved by the U.S. Food and Drug Administration to treat cognitive Alzheimer's symptoms, are meant to boost memory and other cognitive functions by influencing certain chemical activities in the brain.

"Other people should replicate this," Loeb says of his study.

Loeb's group decided to study the antibiotic treatment because one theory suggests the bacterium Chlamydia pneumoniae may play a role in causing Alzheimer's.

But in the study, the antibiotics did not cause a drop in the levels of the bacteria as greatly as would be expected.

Loeb speculates the antibiotics may work by interfering with the accumulation of protein plaques around the brain's neurons, which are associated with the disease. "Or it could be a local anti-inflammatory effect," he says.

Meanwhile, caution was urged by William Thies, vice president of medical and scientific affairs for the Alzheimer's Association.

"It's interesting data," he says. "But there is really no data about mechanism." He adds, "It's a relatively small study, with a relatively short follow-up."

While the idea definitely deserves more research attention, Thies says, "It's not a clarion call to put large parts of the population on antibiotic therapy."

And, he notes, the number of Alzheimer's experts who think the Chlamydia pneumoniae bacteria play a role in the onset of the disease is small. "It's clearly a very small number," he says, "although that doesn't mean it [the concept] isn't right."

More information

For a list of resources for dealing with Alzheimer's, visit the National Institute on Aging or the Alzheimer's Association.

SOURCES: Mark B. Loeb, M.D., M.Sc., associate professor, pathology and molecular medicine, McMaster University, Hamilton, Ontario; William Thies, Ph.D., vice president, medical and scientific affairs, Alzheimer's Association, Chicago; Oct. 11, 2003, presentation, Infectious Diseases Society of America annual meeting, San Diego
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