irreversible antagonist

Definition by Wonder Me!:
Irreversible antagonists bind permanently to receptors. Therefore, even if you put a bunch of agonists to bind to these receptors, these irreversible antagonists won't leave these receptors for the agonists to bind to these receptors.


Clinical example:
- Phenoxybenzamine (at alpha1-adrenoreceptors meaning alpha-1-antagonist!) (1)


Why it works? :
- Phenoxybenzamine permanently binds to alpha adreno-receptors.  Thus, it disables alpha adreno-receptors. Therefore, it helps in Reynauld's disease & HTN caused by phaeochromocytoma (2).

- In Reynauld's disease, "the local fault may involve the alpha 2-adrenergic receptors, which are most important in reflex sympathetic vasoconstriction."  (3)

- "A pheochromocytoma is a rare, catecholamine-secreting tumor that may precipitate life-threatening hypertension." (4) Circulating catecholamines include epinephrine and norepinephrine. These catecholamines cause "vasoconstriction in most systemic arteries and veins (postjunctional α ₁ and α ₂ adrenoceptors)" (5)



Citations:
(1) https://books.google.com/books?id=ThlamNsTDnMC&pg=PA104&dq=%22irreversible+antagonist%22+examples&hl=en&sa=X&ved=0ahUKEwj__YPH1PHLAhXEtIMKHVVlBNwQ6AEIOjAF#v=onepage&q=%22irreversible%20antagonist%22%20examples&f=false

(2) https://books.google.com/books?id=F4-IdTewurIC&pg=PA280&lpg=PA280&dq=%22irreversible+antagonist%22+phenoxybenzamine&source=bl&ots=mRnuVNefvI&sig=dL42U7HMA5HCMY7jA7M4hOP4NfI&hl=en&sa=X&ved=0ahUKEwjUp_im1vHLAhWMuoMKHVwuArcQ6AEIUzAG#v=onepage&q=%22irreversible%20antagonist%22%20phenoxybenzamine&f=false

(3) http://www.ncbi.nlm.nih.gov/pubmed/2022404

(4) http://emedicine.medscape.com/article/124059-overview

(5) http://www.cvphysiology.com/Blood%20Pressure/BP018.htm