The addition of Byetta (exenatide), the first in a new class of diabetes drugs called incretin mimetics, to a thiazolidinedione like Avandia or Actos may improve control of blood sugar in type 2 diabetics, according to a report in the Annals of Internal Medicine.

But in a highly unusual editorial accompanying the story, the journal criticized the trial as "much too short," "much too small," and said many questions remain unanswered.

The researchers led by Dr. Bernard Zinman of Mount Sinai Hospital, Toronto, randomly assigned 233 patients receiving either Avandia or Actos to abdominal injections of Byetta or a placebo twice daily.

Byetta enhances glucose-dependent insulin secretion, and also slows gastric emptying and reduces food intake.

At 16 weeks, adding Byetta to the treatment reduced hemoglobin A1C, the best marker of long-term blood glucose control, by 0.98 percent. It also reduced serum fasting glucose levels and body weight declined by an average of 3.3 lb.

But a total of 35 of the Byetta group discontinued treatment, in 19 cases due to adverse events, compared to 16 discontinuing treatment in the placebo group, and only 3 because of adverse events.

In the accompanying editorial, Dr. Saul Malozowski of the National Institutes of Diabetes and Digestive and Kidney Diseases said the trial was "much too short," "much too small" and said that many questions remained unanswered.

"Small and short studies provide a false sense of safety, because common severe adverse drug reactions may not occur in the condensed timeline and in the limited number of patients," Malozowski said.