Tresa, Well, it may not be the medication that is causing your BP to jump like that. You really need to have that assessed, probably by a cardiologist. Have you tried lying down for a few minutes and taking it and then sitting for a minute and then taking it again? I wouldn't suggest standing with changes in a BP like that! Make a log of that happening, including what happens with your pulse.
There's orthostatic hypotension, which is when your BP drops 20 or more (systolic) when you sit or stand up. And then there's orthostatic hypertension, when your BP goes up 20 or more (systolic) upon siting/standing.
Not so brilliant of someone to order an EMG without telling you to go off of Mestinon first.
The BP seems far more urgent at this point. Can you see someone right away on Monday? Call your primary doctor and see if they can fit you in. They may want to run some basic tests. Please take that one seriously. If you are feeling "weird" when these changes in BP occur, it is absolutely a good idea to go to the ER. You don't want a heart attack or stroke!!

Not to worry you, just to state that changes in BP like that are so not normal.
I hope you have better luck with the next test.
Annie