I see a fair amount of snake bites, mostly copperheads. This year, I have seen fewer snakebites that in the past years, for some reason. The few I've lost to snake bites were all bitten by large rattlers. Two had been bitten on front legs a day or two before they made it to me, and didn't have much of a chance. Necrotic tissue and septic. I don't keep antivenin in stock because of it's expense, and I don't see enough cases that warrant it, so it goes out of date and I have to throw it away. Most cases will need multiple vials, and many owners can't afford it. If I see a case that needs it, there's an emergency hospital not too far away that keeps it. I did have one not long ago that came in with a bite to the face, and had previously been bitten twice and received antivenin. All was going well until the dog just went into acute anaphylaxis that didn't respond to any therapy I gave him. First one I had ever seen go into anaphylaxis with a snakebite. Did some literature research and there is potentially an increased risk of anaphylaxis in dogs that had received prior antivenin therapy. There was also a few mentions of dogs administered the rattlesnake "vaccine" and risk of anaphylaxis with envenomation. So it could be necessary to save the life, but may have a risk of complications with future events.

Hope your pup makes a full recovery.