Drug-induced ED

[Phloston]

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UWorld says sympathetic-blockers (e.g. clonidine, methyldopa, beta-blockers) cause erectile dysfunction. This confuses me because normally erection is PSNS (and emission is SNS).

What's the mechanism?

I'm aware the alpha-agonism can negate the effects of sildenafil, for instance, so I could imagine that unopposed alpha-agonism could occur with beta-blockers.

But what about for the former two drugs?

 

[ijn]

I have no idea. Although apparently many cases of self reported beta blocker ED aren't actually due to the beta blocker. Patients who didn't know they were taking atenolol were less likely than those who knew they took atenolol to report ED (2.5% vs 31%).

http://eurheartj.oxfordjournals.org/content/24/21/1928.full.pdf

When you're dealing with beta blockers or alpha 2 agonists I'd look more toward as yet to be fully elucidated CNS voodoo as the answer rather than peripheral physiology.

 

[Phloston]

Thanks a lot. I appreciate the response.

That's also a good example of a cross-over study.

 

[Big Baller]

This is primarily via activation of 5-HT2 receptors, which inhibit
both noradrenergic and dopaminergic transmission.