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Phthalates in 5-Aminosalicylates: Informing Therapeutic Choice and Minimizing Risk


Geoffrey C. Nguyen, MD, PhD, Associate Professor of Medicine, Mount Sinai Hospital Centre for Inflammatory Bowel Disease, University of Toronto, Toronto, ON.

5-Aminosalicylates (5-ASAs) are considered first-line therapy for mild to moderate ulcerative colitis because of their proven effectiveness and safety profile, even in pregnancy. One formulation, however, contains dibutyl phthalate (DBP) in its coating. Though DBP may cause disruptions in utero reproductive development and other congenital abnormalities in rodents, it is unclear whether it leads to physiologically significant fetal abnormalities in humans. The US Food and Drug Administration has changed its classification for DBP-containing 5-ASAs from pregnancy category B to pregnancy category C to reflect a greater degree of uncertainty regarding its effect in humans. For pregnant women with ulcerative colitis, the most important message is to take their inflammatory bowel disease (IBD) medications to prevent disease relapse, which may have the most adverse effects on pregnancy. Physicians should, however, discuss with young women who are taking 5-ASA with DBP the benefits and risks of switching to another formulation of 5-ASA without the DBP compound.
Key words: phthalates, 5-aminosalicylate, ulcerative colitis, dibutyl phthalate, pregnancy.