A tetracycline antibiotic, doxycycline, has been successfully used to treat a wide-range of bacterial infections. In addition to its effects as an antibiotic, doxycycline has other actions as a drug and, in laboratory studies with animals and with human tissue, can inhibit the degradation of cartilage in a way that could be useful for the treatment of osteoarthritis (OA). OA is a common form of arthritis associated with pain and disability related to the breakdown of cartilage, the tissue in the joint that absorbs shock and promotes smooth movement
On the strength of preclinical evidence, a team of rheumatologists affiliated with six clinical research centers across the United States conducted the first long-term clinical trial to determine the benefits of doxycycline in the treatment of OA--particularly, OA of the knee. Their findings, featured in the July 2005 issue of Arthritis & Rheumatism, suggest that doxycycline may slow the progression of joint damage and point to the need for further research into the drug's effect on the signs and symptoms of this disease.
For the trial, the team recruited 431 overweight women between the ages of 45 and 64 with moderately advanced OA in one knee. The subjects were randomly assigned to receive either 100 milligrams of doxycycline or a placebo twice a day for 30 months. At baseline, the 2 treatment groups were roughly equal with respect to all demographic variables, body mass index, and types of drugs taken for pain, as well as for the x-ray severity of OA in the affected knee and the level of knee pain and functional impairment. OA progression was assessed by measuring joint space narrowing in the medial tibiofemoral compartment through X-rays obtained at baseline, 16 months and 30 months. Severity of joint pain was assessed every 6 months after a washout period of all nonsteroidal anti-inflammatory drugs (NSAIDs) and analgesics.