Metformin response predicts disease progression

NEW YORK (Reuters Health) - In type 2 diabetes patients who are treated with metformin alone, those who achieve low levels of glycosylated hemoglobin level (HbA1c), a common measure of blood sugar, in the first year have a longer period of drug effectiveness, investigators report.

Because diabetes is a progressive disease, patients typically undergo a succession of drug therapy adjustments, Dr. Gregory A. Nichols and his associates point out. If drug effectiveness is maximized at each disease stage, treatment flexibility will be increased and blood glucose levels will be reduced in the long term, they add.

To identify predictors of metformin response, Nichols' group evaluated the records of patients treated between 1996 and 2003 at Kaiser Permanente Northwest HMO in Portland, Oregon. They identified 1,547 patients with diabetes whose first drug was metformin.

According to their report in Diabetes Care, the most important factor predicting long-term success with metformin was the reduction of HbA1c achieved during the first year.

For example, about half of the patients whose lowest blood sugar level was between 7 and 7.9 percent in the first year had to switch drugs or have another drug added within 36 months. In contrast, patients whose blood sugar was less than 6 percent in the first year did not require a switch or another drug for 84 months.

Another important factor that predicted response to metformin was weight loss. The authors found that patients who needed to add or switch drugs lost an average of 1.9 kg, (4.2 lbs) compared with an average loss of 5.0 kg (11.0 lbs) among those who remained on metformin monotherapy.

"Our results indicate that if glycemic control is achieved initially with metformin monotherapy, it can be successfully maintained for several years," Nichols and his associates conclude.

This study was supported by Merck & Company, the manufacturer of metformin.

SOURCE: Diabetes Care, March 2006.