Urinary phthalate metabolite concentrations among men with inflammatory bowel disease on mesalamine therapy.

Background: Phthalates, a family of compounds used in a variety of consumer products, are reproductive and developmental toxicants in experimental animals. One of these phthalates, dibutyl phthalate (DBP), is an inactive ingredient in the coating of Asacol.

Aim: To determine if men with inflammatory bowel disease taking Asacol have higher urinary concentrations of monobutyl phthalate (MBP), a metabolite of DBP, compared to the general population in the United States.

Methods: Five patients at the Massachusetts General Hospital Crohn's and Colitis Center, taking at least 800 mg of Asacol three times a day, provided one spot urine sample. Urinary MBP and other phthalate metabolite concentrations were measured by using online solid phase extraction coupled with isotope dilution high-performance liquid chromatography tandem mass spectrometry.

Results: In four of the five men, the urinary concentrations of MBP (9888 ng/mL, 12,308 ng/mL, 10,124 ng/mL, and 41,590 ng/mL) and of a minor DBP metabolite, mono(3-carboxypropyl) phthalate (MCPP, 116.4 ng/mL, 163.4 ng/mL 72.6 ng/mL, 5604 ng/mL) were orders of magnitude higher than the background concentrations among the US general population. One subject missed his morning Asacol dose and had urinary MBP concentrations (17.5 ng/mL) similar to background levels.

Conclusion: We confirmed that men with inflammatory bowel disease taking Asacol have urinary concentrations of MBP and MCPP much higher than background levels.