There was a neurologist, I believe, from British Columbia, who was "famous" for a comment that went something like, "Mestinon is about as effective in myasthenia gravis as an aspirin is for a brain tumour!"

What he is saying is that Mestinon does not, and cannot control the number of antibodies that our bodies send out. Science isn't positive about what is responsible for that either.

Nor is Mestinon selective. It can't zero in on only weakened muscles, which is why you might feel some muscle twitches in your face (too much?) for example, but it appears to be helping your left arm. This is one of the reasons why, less is more. If we keep taking more and more because we believe it isn't working for a specific area, we could end up in the hospital in "Cholinergic Crisis" which many, many hospital visits are all about.