This may not be shocking to many animal lovers, but pets do not appreciate the joys of chocolate quite as much as humans — probably because it can kill them. Chocolate contains two closely related compounds: theobromine (the primary stimulant) and caffeine, both of which are responsible for chocolate’s energizing effects. These compounds help to stimulate brain and cardiac/skeletal muscle activity, mainly by inhibiting certain cell receptors and enzymes and increasing free calcium concentrations (which helps to power muscles).
At high doses, these effects can cause muscular overstimulation in animals, potentially leading to abnormal heart rhythms, muscle tremors, diarrhea, restlessness, and heart failure. On the other hand, humans are able to break down theobromine much more quickly and efficiently than what a dog’s metabolism is capable of.
Because chocolate is a very common food item for desserts and treats, great care should be taken to keep it out of the reach of dogs, cats, and other animals. Other caffeine-containing products such as coffee should be kept away from pets for similar reasons. They can cause harmful overstimulation as well.