Comparison of two dosage schedules of gold salts in the treatment of rheumatoid arthritis. Relationship of serum gold levels to therapeutic response.

Two doses of gold sodium thiomalate were compared for their effect on rheumatoid arthritis. Thirty-seven patients with active disease for longer than 6 months were treated with 25 mg of gold sodium thiomalate for an average of 29.6 weeks, then at biweekly or monthly intervals to complete 2 years of treatment. Thirty-eight patients were given more than twice as much gold salt at the same intervals on a flexible dose schedule that produced serum gold levels which averaged 332 microgram/dl during the weekly injection phase. No differences were observed in the therapeutic responses of the two groups. Therefore the minimal dose of gold sodium thiomalate required to induce a response in rheumatoid arthritis is 25 mg or less per week. Serum gold levels in the steady state varied between 95 and 386 microgram/dl and were not related to response. Serum half-life for gold was calculated for patients who had an excellent response and for those who were treatment failures. The rate at which gold disappeared from serum was not related to therapeutic responses.