It is vital for patients to discuss all their medications with their personal physician. When it comes to diabetes more than 21 million Americans are affected. After hypertension, many of the commercial drivers that come in for a DOT physical will have pre-diabetes or diabetes. Most patients in general, (including commercial drivers) are not fully aware of the importance of their treatment on their health. For commercial drivers the effect of medication choice on medical certification is also of great importance. Some are not aware that insulin therapy would disqualify them from interstate commerce (for the most part due to the increased risks of hypoglycemia), nor that they would require a Federal Diabetes Exemption from the FMCSA to continue to drive across state lines.  Furthermore, many never discuss their treatment regimen with their personal physician, and do not inform that physician of the impact that treatment choice may have on their commercial driver certification process. What follows is not meant as medical advice or recommendation to any driver or patient. Treatment decisions should only be made with one’s personal physician, and as a medical examiner the role is not to treat but to evaluate a driver’s medical fitness for duty.   Although patients or drivers can not be expected to stay abreast of the latest medical studies, it is important for them to stay involved in their own care and to ask questions about their treatment regimen.   Also, by informing their treating physician of the requirements and rigors of commercial driving, better treatment choices can hopefully be made, since an informed physician if circumstances allow, might be able to choose a treatment or medication that interfered the least with a driver’s ability to continue with his or her livelihood.  More often than not, treating physicians will be unfamiliar with the requirements of commercial driving, opening the door for medical examiners to play a vital role in helping drivers educate their physician.

Brief summary of the JAMA study
This retrospective cohort study from JAMA (Journal of the American Medical Association) published in 2014 investigated the risks of cardiovascular disease and mortality in diabetics already on metformin, when either insulin or a sulfonylurea (glyburide, glipizide, or glimepiride) medication was added to achieve a better glycemic control.

In the JAMA study it is stated that:

The American Diabetes Association and the European Association for the Study of Diabetes recommend that, for patients with preserved renal function, treatment begin with metformin and lifestyle changes to achieve a glycated hemoglobin (HbA1c) level of less than or equal to 7%.

The investigators in this study hypothesized that because insulin is more rapid acting and adjustable, and superior in achieving glycemic control, patients who had insulin added to the metformin rather than a sulfonylurea medication would have lower risks for cardiovascular disease and death. However their findings and conclusion failed to support their hypothesis, with the group on metformin and insulin showing an increased risk of cardiovascular disease and death.
Nevertheless,  drivers should keep in mind that there are many reasons why their doctor may choose insulin rather than another oral medication to treat diabetes. It may be that it’s unavoidable in a recalcitrant type 2 diabetic.  Although more studies are needed to clarify the risks involved with insulin versus sulfonylureas as added co-medications, in certain drivers if better glycemic control can still be achieved with the addition of an oral medication like a sulfonylurea, not only would that benefit them from a commercial driver fitness determination perspective, but as this current study suggests, maybe even from a health standpoint.

Reference:  Association Between Intensification of Metformin treatment With Insulin vs Sulfonylureas and Cardiovascular events and All-Cause Mortality Among patients With Diabetes.  Christianne L. Roumie, MD, MPH; Robert A. Greevy, PhD; Carlos G. Grijalva, MD, MPH; Adriana M. Hung, MD, MPH; Xulei Liu, MD, MS; Harvey J. Murff, MD, MPH; Tom A. Elasy, MD, MPH; Marie R. Griffin, MD, MPH.    JAMA. 2014;311(22):2288-2296. doi:10.1001/jama.2014.4312.