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

Publication of THE LATEST IN ULCERATIVE COLITIS CARE supplement was made possible by an unrestricted educational grant from Aptalis Pharma

Geoffrey C. Nguyen, MD, PhD,

Associate Professor of Medicine, Mount Sinai Hospital Centre for Inflammatory Bowel Disease, University of Toronto, Toronto, ON.


Abstract: 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.

5-Aminosalicylates (5-ASAs) are effective for the treatment of mild to moderate ulcerative colitis and are generally regarded as safe to use, even during pregnancy.
Dibutyl phthalate (DBP) is found in the coating of certain formulations of 5-ASA, and in rodents has been shown to be associated with developmental and congenital abnormalities.
Though phthalates have been shown to be associated with some indicators of reduced masculinization among male fetuses, there is insufficient evidence to prove that it leads to significant harmful effects.
There are several formulations of 5-ASA that do not contain DBP.
Asacol, which contains DBP, is categorized as a pregnancy category C drug, while most other 5-ASAs are in pregnancy category B.
It should be emphasized to pregnant women that taking medications for their inflammatory bowel disease is important because the disease has a strong impact on, not just their health, but the health of their fetus too.
Women of child-bearing age who are taking a DBP-containing 5-ASA should have a discussion regarding the benefits and risks of switching to another 5-ASA, preferably before pregnancy.
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