June 10, 2015
Metformin Reduces Risk of Open-Angle Glaucoma
in Diabetes Patients

Ann Arbor, MI—Medications that mimic calorie restriction might be able to reduce the risks of some other diseases of older age, including macular degeneration, diabetic retinopathy, cataract, or glaucoma, according to past research.

Now, a new study offers some confirmation, finding that metformin hydrochloride used as first-line treatment to lower blood sugar also is associated with reduced risk of developing open-angle glaucoma in patients with diabetes. The report was published online recently by JAMA Ophthalmology.

For the study, University of Michigan researchers examined metformin use and the risk of open-angle glaucoma (OAG), using 2001 through 2010 data on about 150,016 over-40 patients with diabetes. Overall, 3.9% of the participants, enrolled in a large U.S. managed care network, developed OAG.

During the study period, 60,214 patients (40.1%) filled at least one metformin prescription; 46,505 (31%) filled at least one sulfonylurea prescription; 35,707 (23.8% filled at least one thiazolidinedione prescription; 3,663 (2.4 % filled at least one meglitinide prescription; and 33,948 (22.6%) filled at least one insulin prescription.

Some patients filled prescriptions for multiple medications, the study notes.

Patients prescribed the highest amount of metformin—defined as greater than 1,110 grams in two years—had a 25% reduced risk of OAG compared with those who took no metformin, according to the results. The more metformin used, the greater the protective effect: Every 1-gram increase in metformin was associated with a 0.16% reduction in OAG risk, the researchers note.

Generally, the risk of developing OAG is increased by 8% for each unit of increase in glycated hemoglobin level, the study notes. Yet, taking a standard dose of 2 grams of metformin per day for 2 years would result in a 20.8% decreased chance of developing OAG, they suggest, adding that other diabetes medications did not confer a similar OAG risk reduction.

“Although the impact of metformin on risk is known for some traits such as cardiovascular disease, diabetes and some specific cancers, this study points out the importance of understanding the potential impact of CR (caloric restriction) mimetic drugs on the risk of developing other medical conditions that affect older persons,” the authors point out.

“It will also be important to elucidate the mechanisms of metformin action, at both the molecular and clinical level, in the ocular tissues involved in OAG pathology.”

Researchers suggest that metformin may be affecting OAG risk on multiple levels, some involving improved glycemic control and some involving mechanisms outside glycemic control such as neurogenesis, inflammatory systems, or longevity pathways targeted by caloric restriction mimetic drugs.

U.S. Pharmacist Social Connect