Story Tools Send to a Friend Printer Friendly Get PDF Version Write a Comment Read Comments

Related Links

By Megan Rauscher

NEW YORK (Reuters Health) - Treatment with two antibiotics, doxycycline and rifampin, may curb cognitive decline in patients with symptoms of Alzheimer's disease, suggest results of a study presented Thursday at the 41st Annual Meeting of the Infectious Disease Society of America (IDSA) in San Diego.



The findings fuel the belief that infection is involved in the development of Alzheimer's disease. "These two antibiotics have high activity against Chlamydia pneumonia, which is theorized to play a role in Alzheimer's disease," Dr. Mark B. Loeb from McMaster University in Hamilton, Ontario, who led the study, told Reuters Health.

Previous research has shown that C. pneumoniae-infected cells are often and selectively present in areas of neuropathology in the AD brain. This finding, coupled with in vitro findings suggesting that doxycycline and rifampin interfere with the build-up of amyloid beta, led to the current trial, Dr. Loeb said.

Conducted at five centers throughout Canada, the randomized triple-blinded study included 101 patients with symptoms consistent with mild-to-moderate Alzheimer's disease. Fifty-one were randomly assigned to 200 milligrams doxycycline plus 300 milligrams rifampin, and 50 to matching placebo daily for 3 months.

The primary outcome was a change in Standardized Alzheimer's Disease Assessment Scale cognitive subscale at 6 months. Forty-three patients in the antibiotic arm and 39 in the placebo arm completed the study.

The rate of cognitive decline was lower among those taking antibiotics than among those taking placebo. "The difference in scores between the two groups was significant at 6 months, with a p value of 0.034," Dr. Loeb told Reuters Health.

He also noted that the "magnitude of the effect is actually in the ballpark range of the magnitude of the effect seen with cholinesterase inhibitors," the only medications approved by the U.S. Food and Drug Administration and Canadian Health Protection Branch to treat Alzheimer's disease.

Patients in this study were on stable doses of cholinesterase inhibitors but were not responding well to them.

At 12 months, the apparent protective effects of antibiotic therapy on cognitive decline "was actually larger, but the difference between the two groups was not statistically significant," Dr. Loeb said.

Patients treated with antibiotics also showed a "significantly reduced decline in Standardized Mini-Mental Status Exam Scores at 12 months and significantly less deterioration in functional status, depression, and dysfunctional behavior at 3 months," according to the meeting abstract.

There were no between-group differences in C. pneumoniae detection by polymerase chain reaction or antibodies (IgG or IgA).

These findings, Dr. Loeb said, clearly warrant additional studies. "We need more data. This is very interesting information but other groups should be conducting similar or larger controlled trials to see if these findings can be replicated," the researcher said.