Alpha-1 adrenergic receptor agonists are a class of medications used to treat several conditions such as hypotension, vasodilatory shock, cardiac arrest, nasal congestion, eye irritation, and glaucoma.
Alpha-1 adrenergic receptor agonists act on alpha-1
receptors (GPCR proteins) found on vascular smooth muscle and myocardial
muscle. The receptor is coupled with a Gq protein that activates phospholipase
C, which increases the levels of IP3 and DAG that in turn increases the
concentration of intracellular calcium leading to smooth muscle contraction and
glycogenolysis.
The decongestant activity is due to the constriction of
nasal microvasculature, reducing the edema.
The antiglaucoma activity is related to the ability to lower
aqueous production thus decreasing intraocular pressure.
Alpha-1 adrenergic receptor agonists include those used for
a hypotensive crisis, anaphylactic shock, and cardiac arrests like Norepinephrine, Epinephrine, Midodrine, Methoxamine,
those used for glaucoma like Apraclonidine, and those used for nasal congestion
and eye irritation like Naphazoline, Tetrizoline, Oxymetazoline,
Xylometazoline, Phenylephrine, and Pseudoephedrine.
Side effects of Alpha-1 adrenergic receptor agonists include
reflex bradycardia, arrhythmia, hypertension, renal failure, and abnormalities
in gastrointestinal blood flow.
Alpha-1 adrenergic receptor agonists for nasal congestion
are typically contraindicated in patients suffering from hypertension,
arrhythmia, diabetes, benign prostate hyperplasia, and thyroid diseases.
References:
https://www.ncbi.nlm.nih.gov/books/NBK551698/
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