Thats a lotta lorazepam.
I think its possible but without the meto you're more likely to throw up while still awake, and end up having to drink more.
I think the purpose of the other medications are mainly to keep you from throwing up in the first 10-20 minutes, because you'll more than likely throw up once you've passed out anyway. It just gives it more time to absorb and hopefully make you pass out first.
If it were me I wouldn't take the chances without it but that might just be because everything required was already in my possession besides the SN when I chose this method. If you have the time you should think about it.