Effect of sulphapyridine, 5-aminosalicylic acid, and placebo in patients with idiopathic proctitis: a study to determine the active therapeutic moiety of sulphasalazine.

Suppositories of sulphapyridine, 5-aminosalicylic acid, and placebo were used in 45 patients with idiopathic proctitis to determine the active part of sulphasalazine. Each patient used one of the suppositories twice daily for four weeks in a double-blind controlled trial. Complete clinical remission with normal rectal mucosa on sigmoidoscopy occurred in 60% of patients given 5-aminosalicylic acid, but in only 13% and 27% of those given sulphapyridine and placebo respectively. Twelve patients were included twice. In eight of these patients 5-aminosalicylic acid was given one time and sulphapyridine (two patients) or placebo (six patients) another time. Clinical remission occurred in each patient with 5-aminosalicylic acid, but in only one patient during other therapy. The results suggest that 5-aminosalicylic acid is the active therapeutic moiety of sulphasalazine.