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

Background: Phthalates are a family of compounds used in a variety of consumer products. Some phthalates are reproductive and developmental toxicants in experimental animals. One of these phthalates, dibutyl phthalate (DBP) is present as an “inactive” ingredient in the coating of Asacol, a medication commonly used to treat inflammatory bowel disease.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: In 2005, five male patients at the Massachusetts General Hospital Crohn’s and Colitis Center taking Asacol daily 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 (9,888 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, 5,604 ng/mL) were orders of magnitude higher than the geometric mean concentrations among the US general adult population reported for the 2005–6 National Health and Nutrition Examination Survery (NHANES) which is 17.7 ng/mL for MBP and 1.76 ng/mL for MCPP. One subject missed his morning Asacol dose and had urinary MBP and MCPP concentrations (17.5 ng/mL and 5.8 ng/mL) similar to US general adult population levels.Conclusion: We confirmed that a small group of men with inflammatory bowel disease taking Asacol had urinary concentrations of MBP and MCPP that were significantly higher than NHANES reported US adult population levels.