Comparative three-month study of the efficacies of metformin and gliclazide in the treatment of NIDD.

In order to compare the effects of metformin and gliclazide on fasting serum insulin, 60 non-insulin dependent diabetics were included in a multi-centre study. Patients on a diabetic diet alone or a diabetic diet together with a sulphonylurea hypoglycaemic agent, with a fasting glucose greater than 1.4 g/l, on two measurements were included in the study. They were randomly allocated to two parallel groups and received either gliclazide or metformin. They were treated for three months and attended for consultation at one month and three months. The fasting serum insulin level decreased significantly in the group receiving metformin (26.2 +/- 3.2 mlU/L at entry versus 19.8 +/- 2.3 mlU/L after three months: less than 0.01), and increased in a non-significant way in the group receiving gliclazide (21.6 +/- 3 mlU/L versus 26.5 +/- 5 mlU/L after three months: NS). The difference between the two groups was significant (p less than 0.01). There was a comparable significant improvement in blood sugar levels during the three months in both patients receiving gliclazide and metformin. However, significant weight loss (p less than 0.05) occurred only in patients receiving metformin. There was an identical improvement in blood sugar control in both patients receiving gliclazide and metformin over the three months. On the other hand, fasting serum insulin levels decreased significantly in patients receiving metformin compared to gliclazide. The effect of metformin on serum insulin levels is probably due to its action on insulin resistance and its lack of effect on insulin secretion, in contrast to sulphonylurea hypoglycaemic agents like gliclazide.