Variables affecting efficacy and toxicity of sulphasalazine in rheumatoid arthritis. A review.

Studies of sulphasalazine in rheumatoid arthritis have used largely empirical doses. The available literature suggests that the optimum dose appears to be greater than 40 mg/kg/day. Despite the relationship between dose and efficacy and a good correlation between dose and serum concentrations of sulphasalazine and its metabolites, no relationship has been demonstrated between efficacy and serum concentrations of sulphasalazine or its metabolites, although there is some suggestion that higher concentrations on single dosing are achieved in patients who develop upper gastrointestinal symptoms. Furthermore, acetylator phenotype does not affect efficacy, although upper gastrointestinal symptoms are more common in slow acetylators.