Okay, so Chapter Seven: Endocrine/Miscellaneous. In this video, we'll cover alpha-adrenergic blockers and
BPH.
BPH stands for benign prostatic hyperplasia,
and it is a disease typically seen in older men that
leads to prostate growth which then in turn leads to difficulty with urination.
These are the four medications we'll be discussing in this video.
Three of the medications are considered alpha blockers. Alpha is a receptor in the sympathetic nervous system, and
typically, when it is
agonized, it works to
constrict smooth muscle in the bladder neck and prostate capsule, which causes retention of urine.
If we block that, then we'll relax those two muscles and then that will lead to easier urine outflow.
The non-selective alpha blocker is doxazosin, or Cardura.
Since it is non-selective,
since it will also work in the bladder neck and prostate capsule, it also works in the periphery and
it causes vasodilation in blood vessels, which can then also lead to low blood pressure.
There are two selective alpha blockers that we'll be discussing today -
tamsulosin or Flomax and alfuzosin or Uroxatral, and
those are selective for the alpha receptors in the prostate and the bladder.
We can remember that they're specific for the bladder because Flomax
looks like 'max' urine flow, and the alfuzosin,
the Uroxatral, you can think of that as urine control.
The other medication we'll be discussing today is dutasteride or Avodart and that is a 5-alpha-reductase
inhibitor. 5-alpha-reductase is an enzyme that works to convert testosterone to
DHT, the active form of testosterone in the prostate. When we block the 5-alpha-reductase,
then we have less conversion of testosterone to its active form,
which then decreases the obstruction of the urethra by the prostate so then it will then shrink the prostate and lead to
easier voiding of urine.
The steroid stem of dutasteride looks like steroid which can then remind you that it's for men and kind of its
mechanism of action.
Okay, so now we'll go through a couple of practice questions about these medications. Practice question one: 'A selective alpha blocker
that can cause abnormal ejaculation is?' The answers for the next couple questions will remain the same,
so A) will be doxazosin, B) will be tamsulosin,
C) will be alfuzosin, and D) will be dutasteride.
The correct answer is B) tamsulosin.
A) doxazosin is incorrect because it is a non-selective alpha blocker,
and then while alfuzosin is a selective alpha blocker,
it actually doesn't have the ejaculatory
issues that tamsulosin has, so it can be a good option if men are concerned about that side effect.
Dutasteride has a completely different mechanism of action and it is a 5-alpha-reductase
inhibitor.
Now we'll change the question to make each of the other answers correct so question 3 make A) correct: 'An
alpha blocker that can be used to treat hypertension is?' and the correct answer is A) doxazosin.
While B) and C) are both alpha blockers, they have no effect on blood pressure since they are selective for
muscles in the bladder, so those are incorrect. Dutasteride is not an alpha blocker, and it does not affect blood pressure.
Like we discussed before, the doxazosin is not selective
so it also causes vasodilation in the blood vessels so that can lower blood pressure.
This can also cause some of the side effects that we see with it, which is orthostatic hypotension,
which is low blood pressure when moving from a laying to sitting or sitting to standing
position. The doxazosin also has a high risk of first dose syncope,
which is just passing out after you take the first dose of it your body's not used to it.
Question 4 make C) correct: 'A selective alpha blocker that has a risk of drug interactions is?'
A) doxazosin is incorrect because it is a non-selective alpha blocker.
Tamsulosin while it is a selective alpha blocker,
there's not very many drug interactions that we're concerned about. D) dutasteride is incorrect because it is not an alpha blocker.
Alfuzosin is metabolized by the CYP enzymes in the liver so that can lead to a higher risk of drug
interactions. If a patient is on quite a few medications that could possibly interact, this might not be a very good choice.
Question 5 make D)
correct: 'A drug indicated for BPH that works by reducing prostate size is?'
The correct answer is D) dutasteride.
Doxazosin, tamsulosin and alfuzosin all work to relax urinary smooth muscles
and then doxazosin has that other effect of
vasodilation of vessels. Remember that the dutasteride looks like 'steroid',
so it's used in men and it inhibits 5-alpha-reductase which converts testosterone to its active form
DHT.