Steph, This is an older post but I'll answer anyway.

I've taken Mestinon at 90 - 100 mg. every 3 hours round the clock for years now. I honestly haven't noticed any ill effects.

One study done by Dr. James Howard shows that Mestinon does in fact suppress the humoral immune system that produces antibodies.

http://www.ncbi.nlm.nih.gov/pubmed/2540433

http://www.ncbi.nlm.nih.gov/pubmed/15106728

I haven't read anything about Mestinon destroying the acetylcholine receptors. I can imagine that flooding the neuromuscular junction due to taking too much Mestinon - often causing a cholinergic crisis - might do some damage but I can't offhand think of a study for you.

Go to PubMed and dig around. You might have to put in "Pyridostigmine Bromide damage" or something like that. What you might get are articles on Gulf War syndrome.

Annie