Guanethidine

Guanethidine

File:Guanethidine.svg
Systematic (IUPAC) name
2-[2-(azocan-1-yl)ethyl]guanidine
Pharmacokinetic data
Biological half-life	1.5 days
Identifiers
CAS Number	645-43-2
ATC code	C02CC02 (WHO) S01EX01
PubChem	CID 3518
DrugBank	APRD01007
Chemical data
Formula	C10H22N4
Molar mass	198.309 g/mol[[]]
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Guanethidine is an antihypertensive drug that reduces the release of catecholamines, such as noradrenaline. Guanethidine is transported across the sympathetic nerve membrane by the same mechanism that transports norepinephrine itself (NET, uptake 1), and uptake is essential for the drug's action. Once guanethidine has entered the nerve, it is concentrated in transmitter vesicles, where it replaces norepinephrine.

Side effects

Side effects include orthostatic and exercise hypotension, sexual dysfunction (delayed or retrograde ejaculation), and diarrhea.

Pharmacology

Guanethidine is transported by uptake 1 into the presynaptic terminal transported by Norepinephrine transporter (NET). (In this it competes with noradrenaline so can potentiate exogenously applied noradrenaline). It becomes concentrated in NE transmitter vesicles, replacing NE in these vesicles. This leads to a gradual depletion of NE stores in the nerve endings. Once inside the terminal it blocks the release of noradrenaline in response to arrival of an action potential. Spontaneous release is not affected.

Uses

Guanethidine was once a mainstay for hypertension resistant to other agents, but it is now rarely used in the US due to side effects and because substantially better drugs are available. It is still licensed in some countries, e.g., UK, for the rapid control of blood pressure in a hypertensive emergency.

Intravenous nerve block (Bier block) using guanethidine has been used to treat chronic pain caused by complex regional pain syndrome.

References

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