The effect of sulphasalazine withdrawal on rectal mucosal function and prostaglandin E2 release in inactive ulcerative colitis.

We have used in vivo rectal dialysis to assess mucosal prostaglandin E2 (PGE2) release and water and electrolyte transport before and 2 weeks after withdrawal of oral sulphasalazine in eight patients with inactive ulcerative colitis. Although rectal mucosal PGE2 release was unaffected by withdrawal of sulphasalazine, significant reductions in mucosal potential difference (P less than 0.01) and net absorption of water (P less than 0.05), sodium (P less than 0.05), and chloride occurred (P less than 0.05). Clinical assessment showed no change in disease activity. Sulphasalazine withdrawal thus has a detrimental effect on large-intestinal salt and water transport, which does not appear to be mediated through changes in net mucosal prostaglandin production.