The drug most commonly used by
vetrinarians to put household pets to sleep. Only a very small amount of the
chemical is needed and it doesn't take very long for the animal to
pass away painlessly.
There was some controversy about the the possibility of pentobarbitol being found in certain dog foods. This potentially meant that animals being put to sleep with the drug were being put into dog food and that the dogs eating the food were being slowely harmed by the drug, reducing their life span. A US government study found that the levels of pentobarbitol in dog food was not high enough to support these serious charges, though.