An experimental treatment for multiple sclerosis that uses an antibiotic along with a common MS medication may slow the progress of the disease, finds a preliminary study set to appear in the February 2008 issue of Archives of Neurology.

The treatment involved combining doxycycline and interferon, a commonly prescribed MS medication that boosts the immune system and fights viruses.

Many patients with relapsing-remitting MS -- the most common form of the disease -- take interferon, but many still experience relapses and may continue to develop new areas of damaged brain tissue called lesions, one of the key markers of MS.

Dr. Alireza Minagar, of Louisiana State University Health Sciences Center, led a study involving 15 patients with relapsing-remitting MS who had been taking interferon for at least six months and were experiencing symptoms and developing new brain lesions.

For four months, the volunteers took 100 milligrams daily of doxycycline in addition to continuing interferon therapy. They underwent monthly neurological examinations, MRI scans to detect brain lesions and blood work to monitor safety.

After four months, the combination treatment resulted in fewer lesions as visible on MRI -- 60 per cent of the patients had more than a one-quarter reduction in the number of lesions from the beginning of the study.

The patients also had reduced average scores on a test to assess disability levels. Only one patient relapsed.

"Overall, data from this cohort suggest that the treatment combination of oral doxycycline and interferon beta-1a may be safe and effective in some patients with MS; however, further controlled clinical trials are warranted to demonstrate safety and efficacy in a larger patient population," the authors write.

Doxycycline is a member of the tetracycline family, a class of drugs that also includes the acne medication minocycline.

A group of researchers in Calgary is set to begin its own study in January to see whether minocycline could help delay MS.

A small study they completed on 10 patients a few years ago yielded promising results. The researchers are now planning a larger study in 14 Canadian centres to take an in-depth look at the drug in a $4-million, two-year study funded by the MS Society of Canada.

The U.S. researchers believe that tetracyclines may be effective against MS and other inflammatory diseases by inhibiting the action of enzymes that destroy certain nervous system cells, protecting the brain and increasing the effectiveness of the immune system.

MS is a chronic and degenerative condition affecting the nervous system. It is thought to occur as a result of some combination of both environmental and genetic factors.