Afraid to try pepcid (famatodine) -- afraid of heart related side effects

I was dx with MCAS about a year ago. I have POTS and EDS too.

I started on a low histamine diet in September of 2025. Worst mistake of my life. I did not have noticeable sensitivities to food prior to this diet. I would never even have suspected i had MCAS prior to this diet. They tested me for it after i was dx with POTS and EDS bc they are so linked. When i was dx, the doctor suggested a very low histamine diet might reduce my headaches and brain fog.

Alternatively, it has ruined my life. my MCAS symptoms are worse than ever. the limited diet has totally destabilized my mast cells. its horrible.

I am down to 5 foods, and when i tried to eat a new food on Tuesday my heart rate dropped to the 40s and i was rushed to the ER. nothing they could do, of course, and completely unfamiliar with MCAS.

i take claritin 10mg 1x a day. i have been meaning to try pepcid. but i am terrified that because it works on mast cells in the heart, it could cause another autonomic reaction for me if i do not tolerate it well. i am so scared. im afraid it will drop my hr again or give me an arrythmia. i dont know what to do.

i have a consult with "root causes" tomorrow to discuss LDN or ketotifen. I am so confused and scared.