Double blind, placebo controlled study of metronidazole as a disease modifying agent in the treatment of rheumatoid arthritis.

Anecdotal reports suggest that metronidazole may have disease modifying activity in the treatment of rheumatoid arthritis. To assess possible beneficial effects a double blind, comparative trial of metronidazole and placebo was performed. Fifty patients with active rheumatoid arthritis were randomly allocated to receive active drug (n = 24) or placebo (n = 26) and reviewed at weeks 0, 1, 4, 8, 12, 16, and 24. Detailed assessment of drug safety, biochemical and haematological parameters, and efficacy was made at these dates. Dose regimen was 400 mg twice daily from weeks 0 to eight, increasing to 400 mg three times a day from weeks nine to 24 provided that no adverse effects were recorded. Most patients were unable to tolerate metronidazole because of side effects or lack of efficacy, with only five (21%) continuing to take the drug at 24 weeks. For those patients attaining 12 weeks of treatment an overall improvement in articular index and morning stiffness was found. No improvement in laboratory indices of disease activity was seen, however. In this study metronidazole did not have disease modifying properties and was unacceptably toxic.