All higher forms of animals have an endocannabinoid system (ECS). Every animal from humans, to slugs have the basic components of the ECS; namely, endocannabinoids, CB receptors, and corresponding enzymes.

While all animal's endocannabinoid system functions in much of the same way, there are differences between species we need to take into consideration when treating our four legged family member with cannabis.

Dogs

Dogs are especially unique since they have more endocannabinoid receptors in their brainstem and cerebellum than any other species. Humans don't have almost any receptors in the brainstem. That's why it's near impossible to die from an overdose of cannabis. You can't consume enough for that to ever be an issue.

But for a dog, excessive amounts of THC could affect their heart rate, breathing, and muscle coordination. A dog could even lose bowel and bladder control. It's not uncommon to find them swaying back and forth and struggling with balance. These symptoms of a toxic overdose can last from a few hours, to days (during which time your dog might not be able to eat or drink for himself). 

Cats

Cats, on the other hand, are safer than dogs because they react to a THC overdose like a human. However, their experience may be worse because they're so small. 

The Bottom Line

It's rare (I would say it's impossible, but just in case...) for a pet to die from a THC overdose, but because dog's have active receptors that control vital organ function, and due to cat's small size, it's best to start with as little THC as possible. Starting with medicine with 0.3% THC or less is best. We recommend not administering THC to your pet without supervision, unless the possible benefits outweigh risks.