Cannabis affects the mammalian body through numerous pathways, including those found within the Endocannabinoid System (ECS) and the broader Endocannabinoidome, which encompasses many receptors including the cannabinoid receptors.

The ECS is now thought to be the largest receptor system in the mammalian body and has been found throughout many parts of the body including both the Central and Peripheral Nervous Systems, the Endocrine System, the Gastrointestinal System, the Skin, the Cardiovascular System, Ocular structures, the Reproductive System, etc.

Dogs have long been reported to have a higher concentration of CB1 receptors in certain areas of the brain (particularly the brain stem and cerebellum) than people.  Newer studies that have examined the distribution of CB1 receptors in the canine brain, however, have not supported the theory that dogs have 'more receptors', but rather a greater concentration of CB1 receptors in the cerebellum, the area of tthe brain that controls balance.  This no doubt explains the unique 'sensitivity' that dogs appear to experience upon naive exposure to THC.  As with many medications, it is important to recognize that “the poison is in the dose”, and new studies are looking at the potential therapeutic benefits of using THC in animals, including dogs.  Previous studies have shown that the minimum dose typically required to produce signs of toxicity in dogs, is 0.5mg/kg administered intravenously, however, differences in routes of administration, individual variances, and adaptation, can make knowing the exact dose to avoid difficult.

Pet owners have been using cannabis and cannabis-derived products for several years, through a range of techniques. Some are relatively safe, and others carry a high risk of accidental toxicity.  The most commonly used method is through the use of liquid oils or tinctures that allow for gradual titration of the dose.  Other methods include the use of capsules, edible pet treats (NOT human treats that may contain other toxins such as chocolate, xylitol, or raisins), topicals, and transdermals.  Whichever way a person chooses to treat their pet, they should always discuss their decision with their veterinarian.

Obviously, treatments involving smoke should be avoided, as the smoke is irritating to most pets (not to mention the difficulty of getting most pets to participate willingly).

The use of concentrates, while potentially beneficial, also carries a greater risk of toxicity given the difficulty of controlling the dosage, and the frequent lack of knowledge as to the exact content.  Home-prepared and illicit concentrates may also contain unwanted, and potentially dangerous residues, depending on the extraction technique utilized.

Edibles which contain other toxins (such as chocolate and raisins) should be avoided.  These products can also have very high levels of THC, and increase the risk of toxicities. 

For those edible/treat products made specifically for pets, the biggest concern is the consistency of active ingredient from treat to treat (ie. Was the medication properly dispersed throughout the batch), and whether the heating process caused combustion of some of the cannabinoids, thereby reducing the efficacy.

The use of dried and fresh plant material is generally considered relatively safe, as, without heating (which causes decarboxylation), both THC and CBD remain predominately in their acid-forms of THC-A and CBD-A.  These cannabinoids are not psychoactive and do not cause toxicity.  However, their medicinal effects vary from their decarboxylated forms, THC and CBD respectively.