Cinusti,

The first time I had the EMG and Single FIber EMG they told me to be off my meds for 8 hours...the test results were all normal and later they told me I should have been off the Mestinon for longer.

I was off Mestinon for 72 hours before my last EMG and Single Fiber EMG and they came back positive. You may need to talk with your doctor because you shouldn't just stop taking it without talking with them first. Good luck!
Gabe