Norphed Mechanism of Action

Pharmacology: The catecholamine, noradrenaline, is a direct acting sympathomimetic with pronounced effects on alpha adrenergic receptors and less marked effects on beta adrenergic receptors. It is a neurotransmitter, stored in granules in nerve axons, which is released in the terminations of post ganglionic adrenergic nerve fibers when they are stimulated; some is also present in the adrenal medulla from which they are liberated together with adrenaline. A major effect of noradrenaline is to raise systolic and diastolic blood pressure (which is accompanied by reflex slowing of the heart). This is a result of its Alpha stimulant effects which cause vasoconstriction, with reduced blood flow in the kidneys, liver, skin and usually skeletal muscle. The pregnant uterus also contracts; high doses liberate glucose from the liver and have other hormonal effects similar to those of adrenaline. There is little stimulation of the CNS. Beta-stimulant effects of noradrenaline have a positive inotropic action on the heart, but there is little bronchodilator effect.
Pharmacokinetics: Like epinephrine [adrenaline], norepinephrine [noradrenaline] is inactive when given by mouth, and it is rapidly inactivated in the body by similar processes. When given intravenously it is extensively metabolized and only small amounts are excreted unchanged in the urine of healthy subjects.