Which Is Better, NPL or Glargine?

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Addition of neutral protamine lispro insulin or insulin glargine to oral type 2 diabetes regimens for patients with suboptimal glycemic control, by Katherine Esposito and colleagues. Annals of Internal Medicine 149:531–539, 2008

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

Some patients with type 2 diabetes can control their blood glucose levels through diet and exercise, diabetes pills, or a combination of the two. But many patients eventually need to add insulin to their treatment regimens to get their blood glucose levels under control. Different types of insulin are active in the body for different periods of time. For type 2 diabetes, long-acting insulins are often the first type to be added to regimens including diabetes pills. Neutral protamine lispro (NPL) insulin and insulin glargine are two types of long-acting insulin.

Why did researchers do this particular study?

The researchers wanted to compare the effects of adding either NPL or glargine to the diabetes regimens of patients whose diabetes was not well controlled with pills alone.

Who was studied?

The study included 116 adults with type 2 diabetes who were already taking two types of diabetes pills (metformin and a sulfonylurea pill). The patients had A1C levels (a measure of one's blood glucose levels over a few months) of 7.5 to 10% and fasting blood glucose levels higher than recommended targets.

How was the study done?

Patients continued to receive their diabetes pills and were also given nighttime injections of either NPL or glargine. Insulin doses were adjusted every week until the patients' fasting blood glucose levels were in the target range. The researchers monitored the patients' A1C levels, the number of patients who had an A1C less than 7% (the recommended target), episodes of low blood glucose, body weight, and total insulin doses. Twenty patients in each group also had their blood glucose measured continuously over 3 days with a device that measures glucose every few minutes

What did the researchers find?

There were no differences among any of the factors measured between patients given NPL and those given glargine.

What are the limitations of the study?

The study may have been too small to detect differences in low blood glucose episodes between the two insulins. Only 40 patients had continuous glucose monitoring and only for 3 days. Therefore, it is possible that patients were having low blood glucose levels that did not cause symptoms and were not noticed.

What are the implications of the study?

NPL and glargine insulins result in similar diabetes control when added to treatment with diabetes pills (metformin and a sulfonylurea) in patients whose diabetes is poorly controlled with the pills alone. There was no advantage to using one insulin over the other.

FOR MORE INFORMATION

Insulin

Managing blood glucose

ADA Guide to Insulin and Type 2 Diabetes