SULPHASALAZINE IN THE TREATMENT OF RHEUMATOID ARTHRITIS: RELATIONSHIP OF DOSE AND SERUM LEVELS TO EFFICACY

Previous studies of sulphasalazine in rheumatoid arthritis havechosen an empirical dose based upon its use in ulcerative colitis.In this study we compare the efficacy and toxicity of two doses(1.5 g/day and 3 g/day, 30 patients per group), and attemptto relate efficacy to serum levels of sulphasalazine and itsmetabolites. After six months 24 of the low-dose group and 20 of the high-dosegroup remained on treatment. Greater improvement was seen inthe high-dose group. When dose was expressed as mg/kg, the doseefficacy ratio became more apparent and a dose of >40 mg/kg/dayappears to confer greater benefit. No relationship was demonstrated between serum levels of sulphasalazineor its measured metabolites, and efficacy.We conclude that responseto sulphasalazine in rheumatoid arthritis is dose dependentbut does not relate to serum levels of sulphasalazine, sulphapyridine,or acetyl sulphapyridine. KEY WORDS: Rheumatoid arthritis, Sulphasalazine