Alpha-1: The Straightjacket

Straightjacket, you ask?  Yes!  Because the number one thing you should remember about alpha-1 receptors is that their activation causes constriction.  VASOCONSTRICTION, to be exact.  As you may remember from physiology class, blood vessels are wrapped in a layer of smooth muscle.  The alpha-1 receptors are all over this smooth muscle, and signal it to contract (thus constricting the blood vessel) when the brain says so.

A drug that is an alpha-1 agonist will cause vasoconstriction. How can this be used therapeutically? Glad you asked!  Here are a few therapeutic uses for alpha-1 agonists:

1. Hemostasis. Yes, there are times that we want this to happen!  Epinephrine is used topically during surgery to constrict blood vessels and reduce bleeding.  Go team!

2.  Hand-in-hand with local anesthesia.  Vasoconstriction means that drugs can’t flow out of the area so quickly, so adding an alpha-1 agonist makes the anesthetic effect last longer!

3.  Sniffle-bashing, AKA nasal decongestion!  The main ingredients of many cold medicines, pseudephedrine and phenylephrine, are both alpha-1 agonists.  When they shrink the blood vessels in your nose, you become less congested.

4.  Okay, I lied a little bit.  There is a use for alpha-1 agonists that has nothing to do with vasoconstriction. They do one more thing, and that is they cause the pupils to dilate.  This is called mydriasis. Alpha-1 agonists are often added to the solution squirted on your eyeball at the opthamologist’s office.

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