Pharmaniaga Noradrenaline Mechanism of Action

Pharmacotherapeutic group: Adrenergic and dopaminergic agents. ATC code: C01CA03.
Pharmacology: Pharmacodynamics: The vascular effects in the doses normally used clinical result from the simultaneous stimulation of alpha and beta adrenergic receptors in the heart and vascular system. Except in the heart, its action is predominantly on the alpha receptors. This results in an increase in the force (and in the absence of vagal inhibition, in the rate) of myocardial contraction. Peripheral resistance increases and diastolic and systolic pressures are raised.
The increase in blood pressure may cause a reflex decrease in heart rate. Vasoconstriction may result in decreased blood flow in kidneys, liver, skin and smooth muscles. Local vasoconstriction may cause haemostasis and/or necrosis.
The effect on blood pressure disappears 1-2 minutes after stopping the infusion.
Pharmacokinetics: Two stereoisomers of Noradrenaline exist, the biologically active L-isomer is the one present in Noradrenaline (Norepinephrine) Concentrate.
Absorption: Subcutaneous: Poor.
Oral: Noradrenaline is rapidly inactivated in the gastro-intestinal tract following oral administration.
After intravenous administration Noradrenaline has a plasmatic half-life of about 1 to 2 minutes.
Distribution: Noradrenaline is rapidly cleared from plasma by a combination of cellular reuptake and metabolism. It does not readily cross the blood-brain barrier.
Biotransformation: Methylation by catechol-o-methyltransferase.
Deamination by monoamine oxidase (MAO).
Ultimate metabolites from both is 4- hydroxy-3-methoxymandelic acid.
Intermediate metabolites include normetanephrine and 3,4- dihydroxymandelic acid.
Elimination: Noradrenaline is mainly eliminated as glucuronide or sulphate conjugates of the metabolites in the urine.