As mentioned, antivenin has been in short supply for years. Rattlesnake antivenin has only recently been available again to the veterinary field. For years, only human hospitals were able to obtain any. Besides, it is so expensive (veterinarian's COST is $419.80/vial) for the average pet owner that the one vial we have will doubtfully ever get used, not that 1 vial would treat anything over about 10 pounds anyway. Your average dog of 50# would need about 3-5 vials and most pet owners wouldn't spend that much for something that in all honesty is rarely needed anyway. When my pitbull was bitten by a rattlesnake, all he got was a $25 steroid injection and did just fine.