I was baby sitting a friend's TB mare years ago. Somehow she managed to get bit by a sidewinder on her hip! No, I don't know how a 16-17 hand horse was bitten on the hip, but she was. You could see the fang marks and I found the dead sidewinder in the road, incriminating crescent shaped squish mark.
Notified my friend then called the vet. We cold hosed the area many times a day, actually washed the bite twice a day. Then put mastitis cream in the whole. It's an antibiotic that comes in a tube (like worker) but has a thin tip so that you can just slip it in the hole and dispense the cream. She was on oral and injectable antibiotics as well. No sloughing of skin, just lots of heat, swelling and oozing.
She healed over and was fine. Funny thing, we had dispatched plenty of snakes in the years leading up to that and had never had a bite tilll I agreed to watch this horse while my friend moved.