Hydroxyurea interferes with CGM reading in type 1 diabetes patient: Case Report

Chicago, IL: Hydroxyurea may interfere with the functioning of continuous glucose monitor (CGM) in diabetes patients. The discovery was made following communication between one patient and one physician, setting an example for future similar situations.

Hydroxyurea is an uncommonly used medication for treating certain cancers, sickle cell disease, and thrombocythemia.

This was based on a recent case report published in the journal Diabetes Care, according to which a patient with type 1 diabetes taking hydroxyurea experienced falsely elevated sensor glucose (SG values) using the Dexcom G5 and G6 CGM systems, which led to the recognition of the interferent effect of hydroxyurea.

Dexcom sent notices to clinicians and patients in February 2020 following the report of the case, and additional information was added to the Dexcom website a month later.

The patient, a 69-year-old woman with type 1 diabetes was using an insulin pump (Medtronic Paradigm Revel 723) and real-time CGM (initially Dexcom G5, then G6) took hydroxyurea (1,000 mg daily) for treatment of essential thrombocytosis. She noted that for approximately 6 h after taking hydroxyurea, SG measurements predictably and markedly increased, even while fasting and when the time of hydroxyurea ingestion varied. In addition, the glucose management indicator (7.6%) based on 14-day average SG (170 mg/dL) was significantly higher than concomitant glycated hemoglobin (6.3%, 45 mmol/mol), suggestive of artifactual discordance.

In subsequent testing with the patient wearing both the Dexcom G6 and a different CGM, the Abbott FreeStyle Libre, for 3 days, glucose readings were similar until the patient took hydroxyurea in the fasting state, at which point they diverged. For example, at one point the Dexcom read 254 mg/dL while the Libre showed 128 mg/dL. At another, the readings were 194 mg/dL versus 89 mg/dL, respectively. The Dexcom glucose readings, but not the Libre's, remained high for 6-10 hours following hydroxyurea administration.

"Our case demonstrated for the first time that hydroxyurea is an interferent in a commonly used CGM system, and providers must be aware that these CGM data must be disregarded for several hours after each hydroxyurea administration," wrote the authors. "This medication-induced interference with CGM and by extension hybrid closed-loop insulin delivery is fortunately rare, and these minor limitations pale in comparison with the wide-ranging, unprecedented, and revolutionary benefits that these technologies have afforded to people living with diabetes."

The case report that led to the revision of the device's label in early 2020 was reported by Emily D. Szmuilowicz and Grazia Aleppo from the Division of Endocrinology, Metabolism and Molecular Medicine at the Northwestern University Feinberg School of Medicine, Chicago, Illinois, and colleagues.

Reference:

"Interferent Effect of Hydroxyurea on Continuous Glucose Monitoring," is published in the journal Diabetes Care.

DOI: https://care.diabetesjournals.org/content/44/5/e89