The effect of timing on gliclazide absorption and action

In this study we tried to determine when in relation to meals gliclazide should be taken for optimum hypoglycemic action. Eight non-insulin-dependent diabetics participated in this study during hospitalization for glycemic control. After stabilization of glycemic control on gliclazide, they took a 40 mg tablet of gliclazide either 30 minutes before, immediately before, or immediately after breakfast on 3 consecutive days. We then determined serum gliclazide, glucose and IRI levels at 30-minutes intervals beginning 30 minutes before breakfast and continuing until 2 hours after breakfast. Gliclazide taken 30 minutes before breakfast increased in serum concentration before the meal-induced hyperglycemia, but that taken just before or just after breakfast was poorly absorbed and showed smaller and greatly delayed peaks. When taken 30 minutes before breakfast, gliclazide produced a peak of IRI 30 minutes after the meal; taken immediately before or after, it took twice to three times as long to produce an IRI peak. Postprandial hyperglycemia remained pronounced for a relatively long time when the drug was taken immediately before or after the meal. Based upon the experimental evidence we propose the tentative recommendation that gliclazide is best taken 30 minutes before breakfast.