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Selective Alpha Blockers: Prazosin, Doxazocin, terazosin, Tamsulosin and Yohimbine Explained

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In this video I talk about selective alpha blockers, I start with selective alpha 1 blockers (Prazocin, doxazocin, terazocin, tamsulosin) then I talk about Yohimbine which is a selective alpha 2 blocker…

Hello guys and welcome again uh this video is going to be a continuation to the previous video about alpha blockers so in part one i talked about the non-selective alpha blockers in this video i will talk about the selective ones so let’s start so before we go into drugs i want to add one more idea the alpha 1 receptors have different types so we have the alpha

1 a and alpha 1 d and alpha 1 b the alpha one a and alpha one d are more expressed in the bladder and prostate so more expressed and bladder and prostate alpha 1b is more expressed in the blood vessels yeah so this will help us to understand some of the drugs that i’m going to explain in this video so now let’s talk about prazosine dioxazacin and terazosi those

Drugs are all competitive meaning they compete with the agonist which is the norepinephrine to block the alpha-1 receptors because they are selective for alpha-1 receptors they are they have selective alpha one antagonism and because of that we have less tachycardia that happen with dc drugs so so in the previous video i explained the tachycardia it happens with

By two mechanisms in the non-selective alpha blockers so we have the power reflux tachycardia and we have the antagonism of alpha-2 receptors which give us an increase in the norepinephrine going to the heart so we will get technical idea because of these drugs are more selective to the alpha one this mechanism would be absent so we’d only have the para reflex

Tachycardia and this would give us less tachycardia compared to the non-selective alpha blockers another idea or fact about these drugs is that they are used in the treatment of hypertension because they relaxes the arterial and venous biovascular smooth muscles because the as we know artillery and venous vessels walls have alpha receptors alpha 1 receptors

So because they are selective antagonists for these alpha receptors we would get a decrease in the blood pressure and that would be beneficial for treatment of hypertension another fact is that they are used in a treatment of benign prostatic hyperplasia because they relaxes the prostate smooth muscles so uh because of the prostate having alpha-1 receptors

When they are blocked they would give us a relaxation in these muscle muscles of prostate and they would improve the the urine flow improve urine flow in people who have benign prostatic hyperplasia so that’s why they are used for treatment of that condition and we would get we might get hypotension as an adverse effects in these people because those uh those

Uh type of drugs would give us a decrease in the blood pressure so we would get so you might get hypotension as an adverse effect uh in these people with benign prostatic hyperplasia treated with these drugs those drugs may inhibit ejaculation so we have alpha receptors alpha-1 receptors present in the vast difference and some of them are present in the vast

Difference so when we block those receptors we might get some of the vast difference to relax and we would inhibit the ejaculation uh the half-lives of these drugs process would be three hours tiradine is nine to 12 hours and doxazostin would have the most or the longest shelf life which is about 22 hours now let’s talk about time zolusin so transillusin is a

Competitive meaning it competes with the agonist which is the norepinephrine to block the alpha-1 receptors and it is selective same as the previous drugs so it would have little effect on the alpha 2 receptors and this drug has higher affinity for alpha 1a and alpha 1 d and those are more expressed in the bladder and prostate more expressed and bladder and

Prostate so that’s why this drug would have more effect on prosthetic smooth muscles and it has less effect on the blood pressure because the blood pressure is related to the alpha when b and because it has more effect on the prosthetic smooth muscles this this is used in p9 prostatic hyperplasia to improve hyperplasia to improve urine flow because it relaxes

The prostatic smooth muscles and we would have improved urine flow in the in this uh people but it would have less adverse effects because it would have less effect on blood pressure compared to the processing telos oxy indexes are seen and it also may inhibit ejaculation by the same mechanism because we have alpha receptors in the vas and when we inhibit those we

Might get relaxation of device and we might have an ejaculation inhibition and the half-life is from 9 to 15 hours for this agent finally let’s talk about yohimbine yohan bean is competitive selective alpha 2 antagonist so it would have less effect on the alpha one and more effect on the alpha 2 and it is used in the treatment of orthostatic hypotension because

It have it would increase the plot of pressure and it also used to reverse the anti-hypertensive action of clonidine so clonidine is an alpha 2 agonist so it would decrease the norepinephrine and it would give us a decrease in the blood pressure and johan bean is an alpha 2 antagonist so it would have the reverse effect of the quantity and it is used when

Declining when we have severe hypotension due to clienting so this drug would reverse the anti-hypertensive action of clienting yeah and that’s it for this video thank you guys for watching please like and subscribe and see you in the next video

Transcribed from video
Selective Alpha Blockers: Prazosin, Doxazocin, terazosin, Tamsulosin and Yohimbine Explained By Pharmacology by Dr Mustafa