Study in BMJ Finds Warfarin, Some Diabetes Drugs Don't Mix

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The study used Medicare data to identify patients who took both warfarin and 1 of 2 common sulfonylureas.

Patients who take the blood thinner warfarin in combination with sulfonylureas to treat diabetes can experience more falls, insulin shock and other symptoms, according to a study published this month in the journal BMJ.

Researchers from USC’s Schaeffer Center for Health Policy and Economics and its Price School of Public Policy examined the interaction between warfarin and the drugs glipizide or glimepiride. They found that patients who took 1 of those 2 diabetes therapies as well as warfarin could experience hypoglycemia, which can present as the person appear lightheaded and confused. Persons in this condition are at higher risk of falling or injuring themselves.

The researcher examined Medicare data and found that hospital admissions or emergency room visits were nearly 22% higher when patients took warfarin in combination with 1 of the 2 sulfonylureas. While there were not many hospitalizations when drug-drug interactions occurred, falls were more common.


They used a sample of 465,918 Medicare beneficiaries, and from that group found 2111 patients who took warfarin as well as 1 of the sulfonylureas, using prescription fills as an indicator of use. Among the group, 78 landed in the hospital multiple times; this was especially true among those 65 to 74 years old.

"The take-home message is simply that an interaction can occur that has clinical significance, so providers need to be aware in order to prevent a low blood sugar issue from occurring," said co-author Anne Peters, a professor at the Keck School of Medicine of USC. This awareness can mean the patient has to monitor blood sugar levels more frequently. (However, Medicare does not pay for continuous glucose monitoring.)

Drug-drug interactions that result in trips to the emergency room are of concern to payers, including Medicare. Hospitalization for episodes of hypoglycemia cost an average of $20,500 per stay, the researchers reported, and treatment of falls cost an average of $12,300 per incident.


Peters A, et al. Association between use of warfarin with common sulfonylureas and serious hypoglycemic events: retrospective cohort analysis. The BMJ. 2015; doi:10.1136/bmj.h6223.