Olsalazine in the treatment of active ulcerative colitis: a placebo controlled clinical trial and assessment of drug disposition.

The efficacy, safety and disposition of olsalazine was assessed in patients with left-sided ulcerative colitis or proctitis in a double-blind placebo controlled trial. Thirty patients with a mild-to-moderate attack of ulcerative colitis were randomly allocated to olsalazine capsules, 1 g b.d., or placebo for 6 weeks. Good clinical response was found in six patients receiving olsalazine and in two receiving placebo. Improvement in sigmoidoscopic findings and histological appearance of rectal biopsies was also seen more often in olsalazine-treated patients. Plasma concentrations of olsalazine were significantly higher in patients who improved. Olsalazine showed an advantage over placebo which needs to be confirmed by further studies; it was safe in sulphasalazine-sensitive patients but appeared to cause watery diarrhoea in two patients.