A Double-Blind Clinical Trial to Compare the Effects of 4-Aminosalicylic Acid to 5-Aminosalicylic Acid in Topical Treatment of Ulcerative Colitis

Abstract

5-Aminosalicylic acid (5-ASA) is the active component of Salazopyrin and induces a prompt and excellent improvement, when administered as high dosage enema, in patients suffering from active ulcerative colitis. However, the high instability of this metabolite makes its large use difficult. We aimed at finding a more stable preparation and therefore wondered whether another similar molecule, i.e. 4-aminosalicylic acid (4-ASA, generally known as 4-aminosalicylic acid, PAS), which differs from 5-ASA only for the position of the amino group, might be a valid alternative. Therefore, 4-ASA at 2 g dosage, administered as rectal enema, was compared to an equivalent preparation of 5-ASA. We carried out a double-blind therapeutical trial, in which 63 patients, similarly matched for age, sex and extent of disease, took part. The analysis of the final results showed that in the 5-ASA group, 26 (81%) out of 32 patients improved clinically, 25 (78%) sigmoidoscopically and 15 (46%) histologically. In the group of the 31 patients treated with 4-ASA, 24 (77%) improved clinically, 24 (77%) sigmoidoscopically and 13 (41 %) histologically. Since no difference was registered between the two types of treatment (p = 0.141, χ2 test), 4-ASA could be a possible form of treatment for active ulcerative colitis.