For those of us with MCAS, beta blockers make it worse. It causes a degranulation of the mast cells. Also for me, I'm better off not blocking my bodies compensation of tachycardia to get the blood where it needs to go. But, clonidine is an alternative to beta blockers for those with MCAS. It seemed to make my kidney function get worse and I got severe edema when I was on it. I find that 1/2 of a Tramadol works nicely without hindering necessary function for my POTS, actually calms things down. (But, with different subsets - what works for one may not work for another). I'm super sensitive to meds and supplements and tiny amounts work well for me.