About Noradrenaline Directly acting Catecholamine, Adrenergic Alpha/Beta Agonist, Vasopressor. Mechanism of Action of Noradrenaline Noradrenaline exerts it`s pharmacological action by acting as an alpha (alpha1 & alpha2) and beta (?1, &?3) adrenergic receptor agonist. It is a power full vasoconstrictor and constricts both capacitance and resistance blood vessels. It increases systolic, diastolic and mean blood pressure. It is a positive inotropic drug through its beta1 action and causes cardiac stimulation. It increases stroke volume and improves coronary blood flow.