The effect of gold salts on substance P levels in rheumatoid arthritis.

The effect of gold salt therapy on substance P immunoreactivity levels in plasma and synovial fluid was studied in 42 patients with rheumatoid arthritis. Decreased levels of synovial fluid substance P, although not statistically significant, were found in rheumatoid patients who were currently receiving gold therapy when compared to either those patients previously treated or to those who never received this therapy. In addition, we found that patients who received more than 1000 mg of gold salts had significantly lower levels of substance P in synovial fluid than those treated with lower doses. Our results, therefore, seem to support the hypothesis that gold salts appear to be slow-acting neurotoxic drugs that significantly decrease the intrasynovial concentrations of substance P, a well-known inflammatory neuropeptide, in arthritis patients.