How do medicines for lowering blood pressure affect diabetes?

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Bakris GL, Fonseca V, Katholi RE, et al.: Metabolic effects of carvedilol vs metoprolol in patients with type 2 diabetes mellitus and hypertension: a randomized controlled trial. JAMA 292:2227-2236, 2004.

What is the problem, and what is known about it so far?

People with diabetes have a high risk for heart and blood vessel problems that can be caused by high levels of blood glucose and high blood pressure, among other things.

Medicines called beta blockers help lower blood pressure. They often are prescribed to patients with diabetes, along with other kinds of medicines that lower blood pressure. But some beta blockers have been shown to increase blood glucose in people with diabetes.

The researchers wanted to study the effect of two different beta blockers on blood glucose control in people with high blood pressure and diabetes.

Who was studied?

The study involved 1,235 people between ages 36 and 85 with type 2 diabetes and high blood pressure. These people were already taking one of two medicines to help lower blood pressure that are often given to people with diabetes. These are called ACE inhibitors and ARBs. People who had serious heart and blood vessel disease, lung disease, or kidney disease were not included.

How was the study done?

The patients were put in one of two groups. One group took a beta blocker called carvedilol, and the other group took a beta blocker called metoprolol. All of the participants kept taking their ACE inhibitor or ARB medicine, but stopped taking all other medications.

Researchers kept track of patients’ blood pressure. Patients kept taking the beta blockers for 5 months once blood pressure goals were met.

The researchers looked for changes in glycated hemoglobin (A1C), a measure of long-term blood glucose control. They wanted to see how the A1C changes were different in the patients who took the two different beta blockers.

What did the researchers find?

A1C was lower among those who took carvidilol than metoprolol.

What were the limitations of the study?

The study was done over a short period of time. The effects of the beta blockers on a person's health need to be compared in long-term sudies.

What are the implications of the study?

People who want to control their type 2 diabetes and lower their blood pressure without increasing their blood glucose could think about taking the beta blocker carvedilol.