F.inst D. Canine Behaviourist Chocolate made for human consumption can cause death in dogs.
Dogs are sensitive to a class of chemicals called methylxanthines.
Caffeine and theobtomine are members of that family. Dogs simply cannot metabolise and excrete methylxanthines as efficiently as humans. The half life of those compounds in the human body is in the order of 2 to 3 hours, in the dog it is more like 18 hours. In a dog the compounds are taken up by the liver and transmitted via the bile into the intestine. They are then converted back into the original methylxanthines for another circuit through the animal.