Vidyya Medical News Service
Volume 5 Issue 283 Published - 14:00 UTC 08:00 EST 10-Oct-2003 Next Update - 14:00 UTC 08:00 EST 11-Oct-2003
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Antibiotic therapy for Alzheimer's?

The Alzheimer's Association expressed caution about new research on two antibiotics as possible treatments for Alzheimer's disease based on a study presented today at the Annual Meeting of the Infectious Diseases Society of America (IDSA).

"The data in the study are certainly provocative in this relatively new area of Alzheimer treatment research," said William Thies, Ph.D., vice president, Medical and Scientific Affairs for the Alzheimer's Association.

However, Thies added that the relatively small size of the study precludes generalization to the larger population of people with Alzheimer's disease. There is not enough data for the Alzheimer's Association to recommend antibiotic treatment to physicians, patients and families.

"The Alzheimer's Association is looking for large, well-controlled clinical trials before we can make any recommendation one way or the other about the potential of these two antibiotics as treatments for Alzheimer's disease," Thies said. "It is just too early in the process at this point."

Until then, the Alzheimer's Association keeps an open mind about the possibility that this approach, and others, may someday prove to be effective in some cases.

"The Alzheimer's Association enthusiastically supports research for additional and alternative strategies to intervene with the devastating effects of Alzheimer's disease," said Thies. "Since its founding in 1980, the Alzheimer's Association has been a strong advocate for the development of a broad spectrum of interventions for all stages of the disease."

The Alzheimer's Association, through its scientific program, has been a champion of drug development using different approaches and exploiting a variety of different mechanisms of action. "The eventual goal is to create multiple treatment options so that physicians can find a therapy that works safely and effectively for every person with the disease," Thies said.

Newly published research suggests that 4.5 million Americans now have Alzheimer's disease. As the baby boom generation ages, the estimated Alzheimer prevalence is 11.3 million to 16 million by 2050. "The discovery of effective new interventions is urgently needed to stem the tide of the pending worldwide epidemic of Alzheimer's disease," Thies said.

Background on the Study

The study, titled "A Randomized Controlled Trial of Doxycycline and Rifampin for Patients with Alzheimer Disease," by Mark Loeb, MD. MSc of McMaster University, Hamilton, Ontario, Canada and colleagues was presented at the 41st annual meeting of the IDSA in San Diego.

Researchers studied 101 people with suspected mild to moderate Alzheimer's disease at five clinics throughout Canada. In the study, 50 patients received placebo pills, and 51 were assigned to take 200 mg of doxycycline and 300 mg of rifampin daily for three months. The patients, physicians and study investigators were not aware who was taking which pills.

A well accepted Alzheimer's disease test the Standard Alzheimer's Disease Assessment Scale cognitive subscale (SADAScog) was given to the patients to determine mental function before the study began. Six months later, the test was re-administered to 43 people in the antibiotic group and 39 people in the placebo group the remainder had dropped out, died or otherwise did not complete the study. The scores of those in the antibiotic group declined by an average of 2.75 points less over six months than those who received the placebo (on a 70-point scale). The difference in scores between the two groups was statistically significant. At 12 months, there was still a difference between the two groups, although it was not considered statistically significant.

According to the researchers, adverse effects, including nausea, diarrhea and sleep disturbances, were relatively minor and there was no significant difference in their incidence between the two groups.

Previous research, including studies presented at the 8th International Conference on Alzheimer's Disease and Related Disorders in 2002, suggested that the bacterium Chlamydia pneumoniae may play a role in causing Alzheimer's disease. The two antibiotics examined in this study are considered very effective against this germ. However, the study found no evidence that levels of that bacterium were reduced as significantly as would be expected. The researchers suggest that the antibiotics may work by interfering with the accumulation of amyloid plaques around the neurons in the brain, or the anti-inflammatory effects of these antibiotics may provide some relief in Alzheimer's.

"More research is needed to uncover the actual mechanism leading to the results in this study," Thies said.

Plaques made mostly of protein fragments called beta amyloid are found in the spaces between nerve cells in the brains of people with Alzheimer's disease. While researchers still do not know what causes Alzheimer's, it is widely believed that the production of amyloid plaques is a central feature of the disease. Some laboratory studies have shown that rifampin may inhibit the buildup of amyloid. Studies in animals have shown that therapeutic strategies aimed at reducing amyloid aggregation may be effective in reducing amyloid pathology.

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