Coadministration of co-trimoxazole with sulfonylureas: hypoglycemia events and pattern of use.

BACKGROUND Coadministration of co-trimoxazole with sulfonylureas is reported to increase the risk of hypoglycemia. METHODS We identified a cohort of Medicare beneficiaries aged 66 years or older who took glyburide or glipizide for diabetes from a 5% national sample of Medicare Part D claims data in 2008 (n = 34,239). We tracked each participant's claims during 2008-2010 for a co-trimoxazole prescription and subsequent emergency room visits for hypoglycemia. Descriptive statistics and logistic regression modeling were used to evaluate hypoglycemia-related emergency room visits after coadministration of co-trimoxazole with sulfonylureas and its utilization patterns in older adults with diabetes. RESULTS Sulfonylureas users prescribed co-trimoxazole had a significant higher risk of emergency room visits for hypoglycemia, compared with those prescribed noninteracting antibiotics (odds ratio = 3.89, 95% confidence interval = 2.29-6.60 for glipizide and odds ratio = 3.78, 95% confidence interval = 1.81-7.90 for glyburide with co-trimoxazole, using amoxicillin as the reference). Co-trimoxazole was prescribed to 16.9% of those taking glyburide or glipizide during 2008-2010, varying from 4.0% to 35.9% across U.S. hospital referral regions. Patients with polypharmacy and with more prescribers were more likely to receive co-trimoxazole. Patients with an identifiable primary care physician had 20% lower odds of receiving a co-trimoxazole prescription. Hospital referral regions with more PCPs had lower rates of coadministration of the two drugs (r = -.26, p < 0.001). CONCLUSIONS Coadministration of co-trimoxazole with sulfonylureas is associated with increased risk of hypoglycemia, compared with noninteracting antibiotics. Such coadministration is prevalent among older diabetic patients in the United States, especially in patients without an identifiable primary care physician.