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beta blockers and impotence?

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pleaseletmepass

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can someone please explain the mechanism behind impotence with the use of beta blockers? i was under the impression that ejaculation was mediated by alpha receptors. thanks.

-plmp
 

docmd2010

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The only thing i can think of that is possible is that maybe there are beta receptors on the vasculature supplying the penis. Sincee beta (probably beta 2) cause vasodilation, blocking them would cause vasoconstriction, and as a result, impotence.
 

SeventhSon

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maybe a PKA signal makes paracrine hormones that somehow modify the action of NOS or PDE? :confused:
 

SeventhSon

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well wait, is impotence the inability to get an erection or the inability to ejaculate? Except in weird circumstances, the former implies the latter, and you are just asking about ejaculation mediation.
 

EricVorheese

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well wait, is impotence the inability to get an erection or the inability to ejaculate? Except in weird circumstances, the former implies the latter, and you are just asking about ejaculation mediation.
Specifically, impotence = inability of male to achieve and/or maintain penile erection.........its assumed that if you can't maintain an erection, you can't ejaculate

kinda like a if-you-can't-point-you-can't-shoot scenario......
 

subtle1epiphany

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Not due to Beta receptors in the penis or the vasculature of the penis, nor is a placebo effect, it has been found as a statistically significant side effect and is dose-dependent.

Beta Adrenergic Antagonists decrease the blood pressure by blocking the Sympathetic Nervous System at either the B1 or B2 receptors (thus decreasing contractility of the heart) and also by inhibition of renin in the kidney (thus mediating vasoconstriction).
Erections require local vasodilation in the genitals, but sufficient blood pressure to maintain that blood.
Other anti-hypertensive medications would cause similar issues, such as amlodipine, sublingual/transdermal nitroglycerine, Calcium Channel Antagonists, etc...

http://en.wikipedia.org/wiki/Erectile_dysfunction
http://en.wikipedia.org/wiki/Beta_blockers

Don't forget that SSRIs seem to cause impotence by a CNS mechanism. This isn't just an effect of Beta-Blockers.

Just applying the pharmacodynamic mechanism for the drug to known human anatomy and physiology is needed.

Hope this helps!
 

Wings4Marie

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^that might work even better.

According to the Kaplan lecturer the DOC is Acebutalol because of its intrinsic sympathomimetic activity.

I think Carvedilol will work too for the same reason.
 
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