Competitive inhibition of beta 1 and beta 2 receptors leads to decreased cyclic AMP production, and therefore a reduction in catecholaminergic effects (chronotrophic, inotrophic and metabolic). In overdose this leads to haemodynamic compromise and cardiogenic shock.
Propranolol has sodium channel blocking properties.
Cardiac voltage gated sodium channel block prolongs the zero phase of the cardiac action potential; leading to widening of the QRS and cause monomorphic ventricular tachycardia (VT), or a Brugada pattern.
Due to propranolol being especially lipophilic, it can pass through the blood brain barrier, causing seizures and coma due to block of neuronal voltage gated sodium channels.
