Venlafaxine poisoning-induced severe hypoglycemia in a non-diabetic patient: a case report

Venlafaxine is a serotonin and norepinephrine reuptake inhibitor (SNRI) used to treat major depressive episodes and anxiety. The risk of hypoglycemia is mentioned in the Summary of Product Characteristics (SmPC) of venlafaxine in the “warnings and precautions” section in diabetic patients. This effect appears neither in the “adverse reactions” nor in the “overdose” section. We herein report a case of severe hypoglycemia with coma in relation to venlafaxine poisoning.  

Case Report:

 A 35-year-old non-diabetic obese woman (BMI, 29 kg/m2) was found unconscious a few hours after ingesting venlafaxine and bromazepam in a suicide attempt. Vital signs on day 1 were as follows: Glasgow Coma score of 7, blood pressure of 99/66 mmHg and heart rate of 100/min. Electrocardiogram showed no abnormality. She was admitted to the intensive care unit. Due to sustained hypoglycemia [0.5 g/L (day1); 0.41 g/L (day2); 0.8 to 1.20 (day3)], she received continuous intravenous 10% glucose infusion for 3 days to normalize blood glucose. Plasma venlafaxine concentration was 11.7 times the upper the limit of therapeutic dose range (UTDR) on day 2 and reached the therapeutic dose range (TDR) on day 6. Plasma bromazepam concentration was 6.7 times UTDR on day 3 and reached TDR on day 8. Alternative etiologies of hypoglycemia were excluded, i.e. hypoglycemic sulfonamide, insulin poisoning, insulinoma, and disease of the adrenal gland, liver and thyroid. She was transferred to a psychiatric unit after one week.

Impairment of blood glucose homeostasis is rarely described with venlafaxine. In our patient, hypoglycemia appeared to be correlated with plasma venlafaxine concentrations and may be explained by increased insulin sensitivity, considering her obesity.

Healthcare professionals should be aware of hypoglycemia induced by venlafaxine or other SNRIs in non-diabetic patients.