I know that beta blockers are contraindicated for MC because as I understand it, they increase myotonia. I am wondering what the mechanism is that causes this,e.g., do they increase potassium, something else??? Are there medictions that can be taken with a beta blocker (such as Metoprolol) that can counter/block the increase in myotonia (such as Diamox?)? I am also wondering what other medicaitons have been found effective to treat medically caused (i.e., caused by thyroid dusfunction, conduction problem vs primarily from anxiety)tachycardia(such as SVT, AVNRT, PVC's).
I've been looking for the actual biochemical reason for avoiding beta blockers. Because they inhibit the release of renin and the production of aldosterone, I suspect they cause potassium to increase. For most people that's a good thing. If you try low doses and don't see an increase in myotonia, then it may not be a problem for you.
Here's a very good article written by Professor Hanna, a myotonia expert in London, which mentions various drugs that can cause muscle problems:
I don't know if taking a prescription normally used for myotonia would cancel out the side effects of a beta blocker. It would probably need to be a loop diuretic which would cause an increase in potassium excretion.
Dr. Tawil would be the expert I would recommend to sort it all out.
Thanks so much Jan. As usual you provide a wealth of knowledge. I look forward to reading the article, but my new computer won't let me access it for some reason at the moment.
I tried mexiletine 150mg on Sat with no problem, but when I took a second dose on Sunday morning with my thyroid medication my HR became very elevated for several hours. Nothing seems to be very easy...
I see you have added the SCN4A mutation to your "type of "myotonia". I have done so as well. I find myself wondering if that combo might have some added medical impact...