Antibiotic Shows Promise for Treating Knee Osteoarthritis

Newswise — A commonly prescribed antibiotic, doxycycline, which is used to treat a variety of infections, may be a promising new treatment for people with knee osteoarthritis not only because of its effect on slowing the progression of structural damage in the arthritic joint, but also because it helps reduce the frequency of increases in joint pain that tend to occur over time, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Orlando, Florida.

In a 30-month trial, investigators studied the effect of doxycycline versus placebo in 431 obese women between 45 and 64 years of age with X-ray evidence of knee osteoarthritis in only one knee at the outset of the study. Study subjects were randomized to receive either doxycycline, at 100mg two times daily or placebo, and knee pain was measured at the start of the study, and then again during a series of semiannual visits over the 30-month period.

The rationale for the study was not based on the antibiotic action of the drug " there is no evidence that osteoarthritis is an infectious disease " but on prior evidence that doxycycline can inhibit enzymes that are involved in the breakdown of joint cartilage in osteoarthritis.

Doxycycline treatment resulted in a 33% decrease in the rate of joint space narrowing in the X-rays. Joint space narrowing is an X-ray feature of osteoarthritis and reflects loss of joint cartilage. In addition, subjects taking doxycycline were significantly less likely to report worsening of pain in the arthritic knee during the course of the trial than those in the placebo group. Furthermore, doxycycline appeared also to have some beneficial effect on symptoms in the subject's other knee " even when X-rays of that joint were normal.

"Our results show that it is possible to conduct a relatively long-term clinical trial of a potential disease-modifying OA drug (DMOAD), with a high rate of retention of subjects in the trial, and excellent adherence to the dosing regimen. This should encourage further studies of such drugs in the future," said Kenneth D. Brandt, MD, Professor of Medicine and Professor of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, Indiana, and principal investigator for the study. "Our findings indicate that osteoarthritis is a disease whose natural history can be modified by pharmacologic therapy and demonstrate that a relationship exists between joint space narrowing and joint pain in this disease."

The American College of Rheumatology is the professional organization for rheumatologists and health professionals who share a dedication to healing, preventing disability and curing arthritis and related rheumatic and musculoskeletal diseases. For more information on the ACR's annual meeting, see http://www.rheumatology.org/annual.