Endocrine Abstracts

Background: Insulin-induced hypoglycemia has been demonstrated to prolong the corrected QT (QTc) interval. Prolongation of QTc interval, especially in diabetic patients using insulin, can cause fatal ventricular arrhythmias. The aim of this study was to evaluate the effects of metoprolol, diltiazem and pilocarpine on hypoglycemia-induced QTc prolongation.

Methods: Thirty rats were randomly distributed into the following five groups: Group 1 (1 ml/kg saline, n = 6), Group 2 (40 U/kg crystalline insulin + saline, n = 6), Group 3 (40 U/kg crystalline insulin + 1 mg/kg metoprolol, n = 6), Group 4 (40 U/kg crystalline insulin + 0.8 mg/kg pilocarpine, n = 6), Group 5 (40 U/kg crystalline insulin + 2 mg/kg diltiazem, n = 6). Three hours after insulin injection, blood glucose level was measured in all groups. Blood glucose <40 mg/dl was defined as hypoglycemia. Electrocardiograms (ECG) were taken in lead I (DI) and QTc was calculated by using Bazett’ s formula.

Results: Group 2 (insulin + saline) showed that they had significantly prolonged QTc interval compared to control group (P < 0.0001). However, treatments of the rats with metoprolol, pilocarpine and diltiazem significantly prevented the prolongation of QTc interval compared to insulin + saline group (P < 0.005, P < 0.005 and P < 0.01, respectively).

Conclusion: The findings of the present study demonstrated the efficacy of metoprolol, pilocarpine and diltiazem in the prevention of hypoglycemia-induced QTc prolongation. These agents may be considered in the prophylactic therapy of high-risk patients who are using insulin.