Metformin More Effective in African-Americans

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The oral medicine metformin (brand name Glucophage and others) is more effective at controlling blood glucose levels in African-Americans than in whites, according to new research published in The Journal of Endocrinology and Metabolism. Metformin is believed to be the most commonly prescribed diabetes drug in the world, with over 60 million prescriptions filled in 2012 in the United States alone.

African-Americans are twice as likely as non-Hispanic whites to be diagnosed with diabetes and have a higher rate of complications, such as kidney failure and lower-limb amputations, according to the U.S. Department of Health & Human Services Office of Minority Health. Despite this, however, diabetes treatment recommendations have been based on studies in which the vast majority of participants were white.


To determine how well metformin controls blood glucose levels in African-Americans, researchers from the Henry Ford Health System looked at medical and pharmacy records from 19,672 people with diabetes who were prescribed metformin between January 1, 1997, and June 2, 2013. The study population included 7,429 African-Americans and 8,783 whites, each of whom received at least two A1C tests (a measure of glucose control over the previous 2–3 months) at least four months apart. Using the records, the researchers estimated each person’s use of metformin and other diabetes medicines, then ran an analysis to determine the change in each person’s blood glucose levels relative to the amount of metformin they were taking.

After adjusting for factors including age, sex, race/ethnicity, body-mass index, baseline A1C (each person’s A1C level at the start of the study period), total time on metformin, and use of other diabetes medicines, the researchers found that the maximum dose of metformin (2,550 milligrams a day) was associated with a 0.9% decrease in A1C in African-Americans, compared to a 0.42% decrease in A1C among whites. The differences between the groups were significant for all baseline A1C values between 6% and 9%.

“When one considers that the goal HbA1c level for individuals being treated for diabetes is less than 7% and that the average starting HbA1c level in our patients was around 7.5%, these differences in treatment response are clinically important. Moreover, since African-Americans are more likely to suffer from diabetic complications when compared with white individuals, it is heartening to observe that metformin is likely more effective at controlling blood glucose in the former group,” said study author L. Keoki Williams, MD, MPH.

Genetic influences likely account for the difference in response to the medicine, the researchers note, highlighting the need to assess the effects of medicines in all populations. Further study is needed to determine whether the larger A1C reductions in African-Americans correspond to larger improvements in health outcomes, the investigators add.

For more information, read the article “Study Finds Metformin Works Better in African Americans” or see the study’s abstract in The Journal of Clinical Endocrinology and Metabolism. And to learn more about metformin, click here.

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