Which substance is used as an antidote for beta blocker overdose?

Glucagon is utilized as an antidote for beta blocker overdose due to its ability to increase heart rate and contractility independently of the beta-adrenergic receptors, which are blocked in cases of overdose. Beta blockers work by blocking these receptors, leading to decreased heart rate and myocardial contractility. When glucagon is administered, it activates adenylate cyclase through a separate receptor pathway (the glucagon receptor), resulting in increased levels of cyclic AMP (cAMP) in cardiac cells. This enhancement of cAMP leads to increased inotropic and chronotropic effects on the heart.

In addition to its effects on heart function, glucagon is particularly valuable in managing beta blocker overdose because it can also help counteract the hypoglycemia that may result from the overdose, as it promotes glycogenolysis and gluconeogenesis in the liver.

Other potential treatments for beta blocker overdose, although not as effective, may include interventions such as intravenous fluids, atropine, and even vasopressors if necessary, but glucagon remains the specific antidote due to its unique mechanism of action.