Norepinephrine - Revision history

Prab at 02:43, 22 March 2025

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 Norepinephrine is a [[hormone]] that regulates [[blood]] pressure]] by causing [[blood vessel]]s to narrow and the [[heart]] to beat faster when [[blood]] pressure]] drops.
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 File:Noradrenergic_neurons.png|Noradrenergic neurons
 File:Octopamin.svg|Octopamine chemical structure
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			<gallery>
			File:Noradrenaline_breakdown.svg\|Norepinephrine breakdown pathway
			File:Synapse_noradrenergique1.png\|Noradrenergic synapse
			File:Blausen_0838_Sympathetic_Innervation.png\|Sympathetic innervation
			File:Noradrenergic_neurons.png\|Noradrenergic neurons
			File:Octopamin.svg\|Norepinephrine
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Prab at 02:10, 13 April 2023

2023-04-13T02:10:34Z

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Norepinephrine is a [[hormone]] that regulates [[blood]] pressure]] by causing [[blood vessel]]s to narrow and the [[heart]] to beat faster when [[blood]] pressure]] drops.

'''Norepinephrine''' (also known as '''noradrenaline''') is a naturally occurring catecholamine neurotransmitter and hormone that plays a crucial role in the regulation of various physiological processes, such as the fight-or-flight response, attention, and blood pressure regulation. It is also used as a medication to treat hypotensive emergencies and septic shock.

==Biosynthesis and function==
Norepinephrine is synthesized from the amino acid tyrosine in a series of enzymatic steps, which involve the conversion of tyrosine to L-DOPA by tyrosine hydroxylase, followed by the conversion of L-DOPA to dopamine by DOPA decarboxylase, and finally, the conversion of dopamine to norepinephrine by dopamine β-hydroxylase.

Norepinephrine acts as both a neurotransmitter and a hormone. As a neurotransmitter, it is involved in regulating attention, alertness, and arousal. As a hormone, it is released by the adrenal medulla and contributes to the fight-or-flight response, increasing heart rate, blood pressure, and blood flow to muscles.

==Pharmacology and clinical uses==
As a medication, norepinephrine is primarily used as a potent vasoconstrictor to treat hypotensive emergencies and septic shock. It acts on α<sub>1</sub>-adrenergic receptors, causing constriction of blood vessels, which increases blood pressure and improves tissue perfusion. Norepinephrine also has β<sub>1</sub>-adrenergic receptor agonist activity, which can result in an increased heart rate and contractility.

==Side effects==
Norepinephrine can cause a range of side effects, including:

* Increased heart rate (tachycardia)
* Irregular heartbeats (arrhythmias)
* High blood pressure (hypertension)
* Anxiety and restlessness
* Headache
* Nausea and vomiting
* Sweating
* Shortness of breath

More severe side effects may include:

* Chest pain (angina)
* Heart attack (myocardial infarction)
* Stroke
* Tissue damage at the injection site (extravasation)
Healthcare professionals should closely monitor patients receiving norepinephrine to minimize the risk of adverse effects.

==Contraindications==
Norepinephrine should not be used in patients with a known hypersensitivity to norepinephrine or any of its components. It is also contraindicated in patients with uncontrolled hypertension, pheochromocytoma, or certain types of cardiac arrhythmias. Caution should be exercised when using norepinephrine in patients with coronary artery disease, peripheral vascular disease, or hyperthyroidism.

==Drug interactions==
Norepinephrine may interact with other medications, including:

* Monoamine oxidase inhibitors (MAOIs), which can potentiate the effects of norepinephrine and lead to hypertensive crises
* Tricyclic antidepressants, which may also potentiate the effects of norepinephrine
* α- and β-adrenergic antagonists, which may counteract the effects of norepinephrine
* Ergot alkaloids, which may increase the risk of peripheral ischemia when used concurrently with norepinephrine
==See also==
* [[Epinephrine]]
* [[Catecholamine]]
* [[Adrenergic receptor]]
* [[Neurotransmitter]]
==References==
<references />
{{Reflist|30em}}

[[Category:Pharmacology]]
[[Category:Drugs]]
[[Category:Hormones]]
[[Category:Neurotransmitters]]
[[Category:Catecholamines]]
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