Propanolol: LOL!

Get it?  LOL?  Bahahahaha!  Sigh.  Fine.  Well that’s a great way to remember beta blockers, because every last one of them has a generic name that ends in -lol.  This is a great example of why memorizing the generic names of things, instead of the trade names (these are the capitalized ones I put in parentheses), helps you immensely with categorizing drugs like lightning!

Propanolol (Inderal) is the prototype of 1st Generation Beta Blockers.  Propanolol is still prescribed for many things, including hypertension, angina pectoris, and stage fright.  Although it is very effective, it is not the number one drug of choice.  This is because, bless its heart, propanolol is non-selective. It likes both beta-1 and beta-2 just the same!  Can you think of a reason why this might be a problem?

Let’s start with the main therapeutic features of propanolol:

You already know it’s effects on the heart, because you know what the beta-1 receptors do:

1.  Negative Chronotropic (slows the heart rate)

2.  Negative Inotropic (eases the force of contraction)

3.  Negative Dromotropic (slows the rate of conduction)

And the effect of beta blockade on the blood vessels:

4.  Secondary Vasorelaxation (or reducing the amount of resistance from the blood vessels)

You may also remember that there are beta-1 receptors on the kidneys, so:

5. Renin inhibition (stop kidney/heart-controlled vasoconstriction)

But, propanolol also inhibits beta-2!

6.  Bronchoconstriction (anti-bronchodilation, to be more exact)

7.  Uterine relaxation (For our current purposes, just keep this one somewhere in your mind where you store those “fun facts”.  In general, no one gives much of a hoot about beta blockers’ effects on the uterus.  Sigh.)

Those are all the main effects of propanolol on your body!  In summary, they help relieve high blood pressure by loosening the blood vessel walls and stopping renin release, AND help make your heart a better pump by slowing it, letting it relax, and stopping its “go” signal.  All of this adds up to two main therapeutic uses:

1.  Reduced Cardiac Output, which with a little help, leads to…

2.  Antihypertension

But wait, what about the side effects?  For now, just think about that question.  See if you can come up with four possible adverse effects of propanolol, just by looking at what it does!


2 thoughts on “Propanolol: LOL!

  1. #7. You’ll see obstetricians prescribe the beta-2 blockers to inhibit uterine contractions when the Dr is trying to get a pt with premature contractions/early labor under control–to stop early contractions. We see this in 2014 still.

    1. Actually, beta AGONISTS like terbutaline are used to inhibit uterine contractions. Common confusion, due to an agonist doing something inhibitory! Beta blockers do not have too much of an effect.

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