Mechanism of action:
1. It is an adrenergic neuronal blocking agent. It is collected in adrenergic nerve terminals, where it stimulates norepinephrine release firstly but then causes inhibition of the release of norepinephrine in response to neuronal stimulation.
2. It also has direct electrophysiologic effects on heart.
1. Promoted duration of ventricular action potential and effective refractory period is more pronounced in ischemic cells.
2. It also causes an increase of action potential duration and effective refractory period of atrial muscle and AV node.
3. Some positive inotropic effect is also observed from initial release of norepinephrine.
It is used for those life threatening ventricular arrhythmias which are unresponsive to other therapy.
Orthostatic hypotension (adrenergic neuron blocking mechanism), Nausea, vomiting