Are you sure you heard correctly? If so, that is crazy. You need to ask for Isoflurane.
In veterinary medicine,
Pentobarbital is used as an anaesthetic and is dubbed Sagatal; it can also be used in veterinary euthanasia, usually when mixed with other drugs in injectable solutions, branded as
Euthasol, Euthatal, Beuthanasia-D and Fatal Plus to name but a few.
Also read this for more info:
http://www.shooterdog.com/alexfaq3.htm#SURG
DO NOT ALLOW YOUR VET TO USE ANY KIND OF BARBITUATES TO ANESTHESIZE YOUR TOY DOG. MOST PARTICULARLY NOT PENTABARB. Many toy dogs have died needlessly because of UNINFORMED VETS WHO ARE DECADES BEHIND IN USE OF ANESTHETICS FOR TOY DOGS. If your vet thinks Isoflurane is too expensive and refuses to use it, then FIND ANOTHER VET THAT will use it. It could and probably will save your dog's life.