Here’s a bit of free advice, aka I googled it:
http://vcpl.vetmed.wsu.edu/problem-drugs
This discusses drugs that dogs with the mutation can and can’t take, and ones that they CAN take but with a reduction in dose or safe monitoring.
Honestly, I can’t think of a drug that could have straight up killed a dog in an ER setting with solely the MDR1 mutation to blame, unless it was ivermectin, which again, shouldn’t be given in an ER setting. Even if you diagnose demodex, you don’t have to treat right away as it’s not a life-threatening condition. Loperamide should not be given in a ER setting, but maybe I’m alone in that. I don’t treat diarrhea with that nor do any of my ER colleagues. Also, MANY of the drugs that do have neurologic effects can be treated by using intralipid, which IS an emergency treatment.
Anyway… the more you know.