4-Aminosalicylic acid (4-ASA) has been suggested as an effective treatment for both active and quiescent ulcerative colitis. 5-Aminosalicylic acid (5-ASA) is well accepted for the maintenance treatment of inactive ulcerative colitis. Moreover, recent studies suggest that 5-ASA may also be effective in maintaining remission in Crohn's colitis. As treatment with 4-ASA may result in less side effects, the efficacy of a one year's maintenance treatment with oral 4-ASA (1.5 g/d, slow release tablets, n = 19) and oral 5-ASA (1.5 g/d, slow release tablets, n = 21) was compared in a double blind, randomised trial in patients with quiescent Crohn's ileocolitis. Patients with ileocolonic or colonic involvement were enrolled if in stable remission for more than two months but less than one year. Baseline demography and clinical severity were similar in both groups. Total colonoscopy and ileoscopy were performed at enrollment and at the end of the study. After one year seven of 19 patients receiving 4-ASA (36%) and 8 of 21 receiving 5-ASA (38%) had developed a clinical relapse, as defined by a rise in the Crohn's disease activity index (CDAI) of more than 100 points to values higher than 150. The relapse rates between the 4-ASA and the 5-ASA groups were not statistically different although no comparison with the spontaneous relapse rate in a placebo group could be made. Clinical relapse was accompanied by a statistically significant rise in serum concentrations of soluble interleukin 2 receptor and by an increased percentage of activated peripheral blood T cells. There were no statistical differences between the 4-ASA and the 5-ASA groups regarding the height of rise in CDAI or of soluble interleukin 2 receptor concentrations during relapse, thus showing a similar severity relapsed disease activity. In conclusion, 4-ASA maybe as effective as 5-ASA in the maintenance treatment of quiescent Crohn's disease and there were no differences in the severity of relapse between both treatment groups.

The effect of para-aminosalicylic acid-C (PAS-C, 8 g/day) on lipid metabolism was studied on a metabolic ward in nine subjects with primary endogenous hypertriglyceridemia. During 2 wk on a basal isocaloric liquid formula diet (40% fat, 45% carbohydrate), PAS-C reduced plasma triglyceride (-41.9 +/- 18.9%, p less than .01, -x +/- SD), cholesterol (-22.8 +/- 12.9%, p less than .005), and a very low density lipoprotein triglyceride (p less than .001) and cholesterol (p less than .01) levels without changing the cholesterol content of low density or high density lipoproteins. Similar effects occurred on a fat-free, 85% carbohydrate diet. Decreases in very low density lipoproteins correlated with changes in both total triglyceride (r = .99, p less than .01) and cholesterol (r = .70, p less than .05). Treatment with PAS-C reduced the plasma triglyceride removal rate related to lipoprotein lipase (-14.6 +/- 14.1%, p less than .02), but did not alter plasma postheparin lipolytic activity or the apparent Km for substrate-enzyme interaction. Kinetic data obtained during the prolonged heparin infusion fit the linearized Michaelis-Menten model for subjects with endogenous hypertriglyceridemia. The reduction in the plasma triglyceride concentration during PAS-C treatment was a function of the decrease in triglyceride removal rate (r = .74, p less than .025) without alternation in the maximal removal capacity related to lipoprotein lipase. This suggests that under the steady state conditions of these studies, the decrease in plasma triglyceride concentration was due to a reduction in endogenous triglyceride production. Free fatty acid metabolism, glucose homeostasis, fat absorption, and thyroid function did not change. These results suggest that PAS-C lowers plasma triglyceride and cholesterol levels in hypertriglyceridemic subjects reducing endogenous very low density lipoprotein production and/or secretion into the circulation.