Hi,
@Strawberry. I was on Tagamet/Cimetidine for years for my angioedema. I had no problems with it. My doctor did want me to switch to another H2 because (off the top of my head I don't have the exact reason for it, hopefully you'll know what it's about anyways) of Cimetidine and P450. I don't remember what P450 is and I haven't been able to read about mtor yet (perhaps the P450 is involved in it?).
The only reason I switched to Ranitidine was because they changed the inactive ingredients in Cimetidine which I couldn't do. I don't recall any changes in my health from the switch. I'll have to check out old notes some day to see if anything changed and what I might be able to attribute to the H2 switch.
It will be good to hear how this goes for you if you do it (let us know if you can and are up for it), also what Dr. K says, and good to hear anyone else's answer to your question.