**6. Beta-blockers and hypoglycemic drugs**

The use of beta-blockers and hypoglycemic may result in hypoglycemia, hyperglycemia or hypertension. If the use of a beta blocker is required in a diabetic patient, glucose should be carefully monitored. Cardioselective beta blockers (atenolol, metoprolol) cause less disturbance of glucose metabolism and less masking of hypoglycemic effects. Propranolol accounts for the majority of positive reports of interactions and should clearly be avoided.

Hyperglycemia occurs frequently in critically ill patients and it is a marker of poor prognosis (Pitrowsky et al., 2009). The main complication of insulin therapy is hypoglycemia which is considered a potentially serious adverse event in these patients (Diener et al., 2006). The combination of a beta-blocker and insulin may impose a higher risk of blood glucose changes and lead to the development of hypoglycemia, hyperglycemia and hypertension.

Beta-blockers may inhibit some of the normal physiologic response to hypoglycemia. Symptoms of hypoglycemia such as tremors and tachycardia may be absent, making it more difficult for patients to recognize an oncoming episode. In addition, multiple effects on glucose metabolism have been reported, usually with the noncardioselective beta-blockers (e.g., propranolol, pindolol, timolol) but occasionally also with relatively beta-1 selective agents (e.g., metoprolol). Specifically, inhibition of catecholamine-mediated glycogenolysis and glucose mobilization in association with beta-blockade can potentiate insulin-induced hypoglycemia in diabetics and delay the recovery of normal blood glucose levels. Prolonged and severe hypoglycemia may occur, although these events have rarely been reported. Significant increases in blood pressure and bradycardia can also occur during hypoglycemia in diabetics treated with insulin and beta-blockers due to antagonism of epinephrine's effect on beta-2 adrenergic receptors, which leads to unopposed alpha-adrenergic effects including vasoconstriction. Other effects reported with various beta-blockers include decreased glucose tolerance and decreased glucose-induced insulin secretion (Goodman & Gilman, 2010).
