The only time a pal of mine had to draw his Glock was when a rogue pitbull attacked him while walking in the neighborhood. He shot the crap outta that dog, and it hobbled away and died elsewhere.
If you give them one arm and keep their teeth occupied, you may be able to lift the front of them up and get two feet off of the ground. They are vulnerable underneath. Kick, stab, hit, but make them hurt.
If you've got the bite occupied with your (hopefully) padded arm, will sinking a thumb into their eye socket be effective?