I know someone who is wearing a colostomy bag because of an attempt using diphenhydramine.
Drug attempts are extremely dangerous & inefficient.
There's more of a risk of waking up severely disabled than succeeding.
I don't give recommendations but if it was me I wouldn't do it with drugs at all.
I have 2 attempts using pharmaceuticals & am still here.
You might want to look at some of the megathreads so you can get an idea of what is effective & available but I wouldn't waste my time with diphenhydramine at all.
Whatever choices you make, I hope you find what you're looking for.
Peace & love to you