Several randomized controlled trials (RCTs) have affirmed the efficacy of 5-aminosalicylic acid (5-ASA) and sulfasalazine in the acute treatment of mild to moderate exacerbations, as well as in the maintenance of clinical remission. Initially, common practice was to prescribe 5-ASA in three divided doses. Slow release once daily mesalamine with Multi Matrix System (MMX) technology was shown to be effective in induction and maintenance of remission of adult ulcerative colitis (UC). Since transit time of the colon is much slower than the small-bowel, and since the active ingredient should act locally on the colon, less frequent dosing of the regular formulation may also provide sufficient colonic coverage. Indeed, two recent studies among adults with UC suggest that once daily dosing of mesalamine (Pentasa® and Salofalk®) may be as or more effective than twice daily dosing.