This is chapter six cardio and in this video we'll be discussing beta adrenergic
blockers by generation.
Beta blockers are a pretty common drug class, and they're
especially used for patients who have heart failure and in patients after they have had a heart attack
We'll have four examples of medications today - three
of them will be considered beta blockers, and then we'll also compare that to an alpha blocker.
Alpha and Beta are different receptors that are seen in the sympathetic nervous system, and
there are two different types of beta receptors.
Beta1 is a receptor that is found in the heart, and
when we stimulate that we increase heart rate.
Beta2 receptors are found in the lungs, and when
we stimulate that we see bronchodilation or improvement of breathing.
So, if we were to block beta1,
we would see a decrease in heart rate, and if we block beta2, that would actually be bad and we would see
bronchoconstriction
in the lungs.
We have three different generations of beta blockers. Our first generation of beta blocker is propranolol or Inderal.
First generation just means that it is non-beta selective.
It's good that it hits beta1 in the heart to lower the heart rate,
but it's bad in that it hits beta 2 in the lungs, so then we get bronchoconstriction.
We can remember how propranolol works by hitting both beta1 and beta2
by remembering the brand name Inderal, and the ending Says '-al' or 'all' the beta receptors. Our
example of a second-generation beta blocker is metoprolol.
There's two different brand names - there's Lopressor and Toprol XL -
and metoprolol is a beta1 selective, otherwise known as a cardioselective beta blocker.
It works in the heart to decrease heart rate.
Unfortunately, when we lower our heart rate, our body compensates by
constricting our arterioles which can then lead to a slight increase in blood pressure.
There's two salt forms of metoprolol - the Lopressor is metoprolol tartrate
which is short acting and is dosed twice daily,
then the Toprol XLis the metoprolol succinate
salt form and that's long acting, so we can remember that one is the long acting because the brand name ends in XL.
Our example of a third-generation beta blocker is carvedilol or Coreg.
Third generation blocks both beta1 and beta2,
so we get a decrease in heart rate, but we
Also get that bronchoconstriction. It also blocks alpha1, so since it blocks alpha, it leads to
vasodilation which can better control blood pressure.
We don't see the typical stem of '-olol' with carvedilol -
We see the 'i' instead of the 'o' - but
we can remember that carvedilol works a little bit differently by remembering the '-dil-' part of carvedilol, so we can think of that as
dilating.
Our last example is just for comparison., it's an alpha blocker. Doxazosin or Cardura is our example.
Alpha blockers work
to relax smooth muscle in the bladder neck and prostatic capsule, so then
we can use this for benign prostatic hyperplasia, which can lead to difficulty urinating,
especially in older men. Doxazosin, since it is a non-selective alpha blocker, can
also be used to lower blood pressure as well with its vasodilatory effects.
Now, we'll go over some practice questions.
'A beta blocker that is an alpha blocker also is?' and then these four answers will remain the same throughout
the rest of the video. A) propranolol, B) metoprolol,
C) carvedilol and D) doxazosin.
The correct answer is C) carvedilol because as you recall, it blocks alpha and beta.
A) and B) are incorrect, propranolol and metoprolol,
because theose both just work on beta. D) doxazosin is
incorrect because it has no effect on beta but it does block alpha.
For the remaining three questions, we will change the question to make each answer correct. Question three,
make A) correct: 'A beta blocker that should
be used with caution in asthmatics is?' and the correct answer is A) propranolol.
Propranolol blocks beta2 receptors in the lungs, so it can lead to bronchoconstriction,
which would be bad in asthmatic patients who already have constriction problems in their lungs.
Metoprolol, carvedilol and doxazosin don't work quite as hard on the beta2 receptors or they
don't quite work there at all, so these can be used just fine in patients who have asthma.
Practice question four: 'A beta blocker that is selective for beta2 receptors in the heart is?'
That correct answer is B) metoprolol because it is beta selective or cardio selective.
Propranolol is incorrect because it
also blocks beta2 in the lungs.
Carvedilol is incorrect
because it is selective for beta1 but it also blocks alpha receptors. Doxazosin is
incorrect because it is just an alpha blocker.
Pratice question four: 'An alpha blocker that can be used for BPH and hypertension is?' and the correct answer is D)
doxazosin. It is an alpha blocker which is indicated for both of those disease states.
A) and B), propranolol and metoprolol, are incorrect because they only work on beta
receptors, and carvedilol, while it does work on alpha receptors, there is no indication for
BPH but it can be used for hypertension