Myasthenia Gravis

[george7222]

Hello All,

Warning: this post contains “Adult Themes”.

I'm trying to get some information out there into cyberspace. This is a problem which I cannot find documented anywhere - I'm hoping writing about it will encourage people to talk about it or investigate it. It is a rather unpleasant subject, and I have never discussed it with anyone.

I'm a 33 year old male, and I've had MG for 15 years. I have been on varying doses of Mestinon for all of that time, and I've been on azathioprine for 13 years. I did have plasmapheresis and Intragam earlier on, but not in the last ten years. I had a thymectomy for a thymoma at the start. On the bright side, I'm doing well. Really no problems except some ongoing mild facial weakness.

In my opinion, Mestinon causes erectile difficulty. Impotence is probably too strong a word – it just makes make things more difficult. I have found that mestinon causes some problems attaining and maintaining an erection.

Getting an erection apparently involves changes in blood vessels of the front bottom, under the influence of the sympathetic and parasympathetic nervous system. Mestinon, as a side effect, activates muscarinic receptors in the body (part of the parasympathetic system), so it makes sense that this would alter the normal processes in some way.

I can’t think of a reason why Azathioprine would be causing the trouble, and I don’t think I’ve got any relevant psychological problems.

In my experience, things work somewhat better when my Mestinon dose has worn off (late at night).

Hopefully someone will see this post and do some proper research in this area.

[amm34]

I am female, so I can't say. But from a physiologic standpoint the question I would ask is once you reach an erection is there any problem with climaxing and ejaculating. The erection itself in under the control of the parasympathetic system, and could theoretically be influenced by mestinon. The climaxing and ejaculation is not controlled by the parasympathetic system, rather the sympathetic. Physiologically you would not expect mestion to affect the ejaculation process. For all you men, if you can try to distinguish where the difficulty lies, you may be on to something. Try taking something like viagra which should 'overrule' the more mild affect expected my mestinon and see if it resolves. good luck.

[george7222]

I don't have any trouble with the climaxing/ejaculation side of things.

When I first got MG my neurologist prescribed some atropine to counteract the muscarinic side effects, but I never really took much of it. When I was trying to sort out the erectile problems I did try taking some atropine, but it didn't seem to help (though that was a few years ago).

I've just been reading about some of the Viagra side effects on blood vessels in the brain, retina, and heart.
I doubt any research has been done on patients taking Mestinon and Viagra, but I wonder whether taking two medications that act on blood vessels ie Mestinon and Viagra, would be entirely safe.

[amm34]

I definitely,in that case think mestinon could be a culprit. Can you get by w/o taking it and try to see if that is the issue? I actually do take atropine, but at least what I have is pretty mild, as you need to be careful with atropine and the heart. It pretty much just helps me with the GI issues...

I would say always be careful with drug interactions. I am pretty sure there are no studies done checking for interactions, so when you plug it into software to check, it passes, but that is likely due to no data. I don't know your field, but you say science... so as a brainstorming exercise.... Viagra works by inhibiting phosphodiesterase type 5, thereby increasing the effects of nitric oxide-activated increases in cGMP. I am not a biochemist, but from all that I remember back to biochem this is a completely different pathway from any mucarinic effects. That is not to say there would be no synergistic or antagonistic effect, but mestinon's effect on blood vessels is certainly less potent. I would say if you are getting bradycardia from mestinon taking a vasodilator is not a good idea, but bradycardia is only a side effect in a small population of mestinon users. Ask your neurologist. If you find out an answer, please do share b/c that is a curious question I would like to know the answer to.

[george7222]

Thanks for your thoughts amm34.

To refresh my memory, I've just done a google search for muscarinic receptors. The related wikipedia entry says a lot. Apparently cholinergic receptors are found all through the autonomic nervous system, both in the sympathetic (pre-ganglionic) and parasympathetic parts, and given erection involves an interplay between both, it all makes a bit of sense. Mestinon is probably causing autonomic nervous system havoc.

Related to this somewhat, activation of some muscarinic receptors causes dilation of blood vessels. I'm often told by people I look red in the face. Also, in my early days with MG I found that if I drank alcohol I had EXTREME facial flushing. And I emphasize the word EXTREME again. Very very red face. Though I was on large doses of Mestinon at the time - 15 x 60mg tablets a day. I haven't had this problem in recent years, but my mestinon dose over recent years has been less than 4 x 60mg tablets per day.