There are many issues involved in the consideration of cannabis as medicine, including regulation, product selection and safety.
Cannabis and marijuana are the common names for Cannabis sativa. This annual flowering herb has a long history of being used as a recreational drug as well as for hemp fiber and oils. It also has a long history as medicine.
Cannabis seeds have been found in Siberian burial mounds dating back to 3000 B.C. The plant was used in ancient China, and Hippocrates recommended cannabis extracts for use as medicine.
Queen Victoria’s physician, Sir Russell Reynolds, prescribed cannabis for the Queen’s menstrual cramps. He was quoted in The Lancet, a prestigious British medical journal, as calling cannabis “one of the most valuable medicines we possess”. In the United States, both Presidents Washington and Jefferson grew cannabis as hemp, used to make ropes, paper and clothing.2
In recent years, there has been a resurgence of interest in the medical uses of this versatile plant, for both humans and animals. There are many issues involved in the consideration of cannabis as medicine, however, including regulation, product selection and safety.1
It’s illegal to prescribe cannabis to animal patients in the US
Cannabis was made illegal in the United States in 1937. In the 1970s, the THC portion of the plant was classified by the Drug Enforcement Administration (DEA) as a Schedule I drug, which by definition means the DEA feels it has no medicinal use and a high potential for abuse. Other drugs classified as Schedule I include heroin, LSD and Ecstasy. Schedule I drugs are prohibited from being prescribed by physicians and veterinarians. Interestingly, the drug Marinol, which is composed entirely of synthesized THC, is classed as Schedule III.
Public pressure has more recently driven the legalization of cannabis for both medical and recreational uses. For example, 23 states and the District of Columbia have legalized cannabis for some human medical uses, and the states of Colorado and Washington have legalized recreational cannabis for people over the age of 21.
As of this writing, however, no state allows veterinarians to prescribe cannabis for animals. Veterinarians risk disciplinary action for prescribing or even recommending medical cannabis for pets. However, in states where cannabis is legal either for human medical or recreational use, people can administer it to their own animals since pets are considered property under the law.
Effects depend on the species
There are three separate species within the Cannabis genus – indica, sativa (meaning cultivated), and ruderalis.2 Historically, specific physiologic effects were attributed to each species.3
- Indica – Relaxing, calming. Best used at night. Grows best indoors.
- Sativa – Uplifting, increased energy, hallucinogenic effects. Best for daytime use.
- Hybrids – 95% of all cannabis strains today are hybrids. Different strains mean the possible medical benefits may vary widely.
Components and compounds
There are hundreds of known compounds in the cannabis plant, including cannabinoids, terpenoids, and noncannabinoid phenols. The most important psychotropic part of the cannabis plant is its tetrahydrocannabinol (THC). Cannabidiol (CBD) is important from a medical perspective and has no psychoactive properties.
In 1992, Raphael Mechoulam discovered anandamide; it’s made within the human body and occupies THC receptors.
It was the first of several endocannabinoids found to interact with the neural network in the body, just as endorphins and serotonin do.4 Mechoulam found that exercise increased endocannabinoid levels in the body, probably causing what is referred to as the “runner’s high”. He found that endocannabinoids have important roles in memory, balance, immune function and neuroprotection.5,6 There are more than 85 cannabinoids in the cannabis plant.
The THC content of cannabis grown in the 1960s doesn’t come close to equaling THC levels in the modern plant. Botanists have increased the amount of THC from 3% to 5% in the 60s to around 28% now. THC binds to a receptor in the cerebral cortex known as C-1 and is responsible for the psychoactive effects of the plant. THC is also useful for appetite stimulation and is involved in pain control.
CBD comprises approximately 40% of the plant’s total cannabinoid makeup. It preferentially binds to C-2 receptors but has a low affinity for binding to C-1 receptors. CBD and terpenes can reduce the actions of THC, which in turn serves to reduce the paranoia and increased heart rate associated with larger doses of THC. CBD creates most of its clinical effects by binding to the 5HT1A receptor, which produces antidepressant, anti-anxiety and neuro-protective effects. CBD also has strong antioxidant and anti-inflammatory properties.
Terpenoids are organic compounds found in the plant’s resin, and are present in the essential oils of cannabis. There are over 200 terpenes found in cannabis. In nature, terpenoid oils serve to repel insects and occasionally prevent fungal infection. Terpenes are not only important in producing the smell and taste associated with different strains of cannabis, but are also involved in the effects produced by consumption. For example, beta-caryophyllene is a terpene that binds to a CBD receptor and is useful for both inflammatory conditions and auto-immune disorders. Human patients who have changed strains of cannabis for medical reasons in order to optimize either THC or CBD levels may find that the new strain does not work as well because of a different terpenoid profile. This “entourage effect”, or synergism, of the more than 400 compounds in the cannabis plant highlights the importance of the therapeutic value of the whole plant over its individual constituents.
Because cannabis is classified as a Schedule I drug, there is a lack of research on its clinical use in animals. The effects of THC and CBD have been mostly studied in a laboratory setting. THC has been shown to be useful for many conditions, including epilepsy, cerebral ischemia, motion sickness and cancer treatment. Research has identified CBD as helpful for psychosis, seizures, anxiety, stress, irritable bowel syndrome, arthritis, pain, vomiting, diabetes mellitus, cancer, and the repair of traumatized tissue, among others.7,8 CBD has also been shown to improve sleep quality.
Research has shown that CDB and THC work best in combination, improving each other’s clinical effects. In humans using marijuana for medical use, it is suggested that a THC:CBD ratio of 1:1 be used for both pain relief and appetite stimulation. For those in extreme pain, a ratio closer to 3:1 may be beneficial. The low THC/high CBD strains have the potential to treat PTSD, multiple sclerosis, osteoporosis and dementia. As stated earlier, the synergistic effects of the combined components of the cannabis plant favor using the whole plant over its individual parts.
There are differences between the cannabidiol found in medical cannabis and that in industrial hemp. In medical cannabis, the cannabidiol is extracted from plants grown to be high in CBD and low in THC, and is a Schedule I substance. Cannabis-based CBD oil from these plants is only legal in states that have medical cannabis laws. Conversely, high CBD oil extracted from industrial hemp can be sold in any state, and over the internet.
In the last 50 years, consumers have come to demand a higher THC content in strains for recreational use, so CBD was markedly reduced in the gene pool. As demand then increased for a good medical cannabis product that contained lower amounts of THC and higher concentrations of CBD, Harborside Health Center in Oakland began in 2008 to use gas chromatography and mass spectrometry to identify high CBD cannabis strains for their clients. Currently, several dozen laboratories in states where medical cannabis is legal provide testing services so the consumer can be aware of the CBD and THC content of the products they are consuming. Cannabis dispensaries are providing CBD-rich herbs, edibles, tinctures, extracts and oils. At least one company is also providing CBDrich treats for dogs.
Toxicity in animals
Because of legal restrictions regarding research, few studies have been done regarding the safety of cannabis in animals. There have been no published reports of deaths from the ingestion of cannabis in animals, but there are increasing reports of animals being treated for cannabis overdose, especially in states such as Colorado where cannabis has been decriminalized. Pets are most often exposed to toxic doses because of deliberate administration of edible products, by inhalation of second hand smoke, or by ingestion of unattended quantities of the plant.
Most pets exposed to toxic amounts of cannabis become sedated and uncoordinated, but it is reported that up to 25% of pets suffering from overdose exhibit agitation. In extreme cases, pets need to be rehydrated with intravenous fluids and have their cardiac status monitored while they recover.
For humans, it has been said that cannabis is one of the safest therapeutically active substances known to man. Cannabis has been shown to be non-addictive and safe for human use. The risk of reaction to medical cannabis is much less than the morbidity and mortality associated with the use of opioid analgesics and non-steroidal pain medications. The use of CBD as part of an integrative pain management protocol can potentially reduce the amount of traditional medication needed.
The dosage of cannabis for people or animals is highly individualized. Considerations include the form of the product (capsule, edible, tincture), the ratio of THC:CBD desired, and the condition being treated. In general, patients with cancer or increased levels of pain require more THC than those with anxiety or seizures. Because of the lack of research, there are no good dosing guidelines available for medical cannabis-derived products for animals. A common sense approach would be to start with very small doses in order to avoid any adverse side effects. When offering edibles to pets, it would be wise to avoid those with potentially toxic ingredients such as chocolate or Xylitol.
An alternative approach would be to use a commercially available hemp product for pets (Treatibles [AD Remedies Inc.], Canna-Pet or CannaCompanion). By definition, the THC level should be low enough to avoid any significant psychogenic effects, while utilizing the benefits of potential CBD levels. Each company proposes dosing for their products based on body weight, and while clinical response can be variable there are very few reported side effects.
Medical cannabis has great potential for clinical use in animals suffering from a wide range of ailments, including pain, seizures, digestive disorders and anxiety. As long as it is classified as a Schedule I drug, however, it will be difficult for veterinarians to safely or legally recommend its use for their patients. Commercially available hemp-derived products have the potential of being very useful, especially with cancer patients.
For more product info
Treatibles (AD Remedies Inc.) – www.treatibles.com
Canna-Pet – www.canna-pet.com
CannaCompanion – www.cannaforpets.com
1Guy GW, et al. “The Medicinal Uses of Cannabis and Cannabinoids.” 2004, Pharmaceutical Press: 74-80.
2Silver RJ. “The Botany & Biological Effects of Cannabis sativa L. in the Veterinary Patient: Information Regarding this Emerging Palliative Therapy.” Proceedings of the 2014 annual meeting of the AHVMA: 444-452.
3Williamson EM, Evans FJ. “Cannabinoids in clinical practice.” Drugs, 2000; 60(6): 1303-14.
4Witkamp R, Meijerink J. “The endocannabinoid system: an emerging key player in inflammation.” Curr Opin Clin Ntru Metab Care, 2014; 17(2): 130-138.
5Pagoda U ,et al. “The emerging role of the endocannabinoid system in endocrine regulation and energy balance”. Endocr Rev, 2005; 73-100.
6De Laurentiis A, et al. “Endocannabinoid system participates in neuroendocrine control of homeostasis.” Neuroimmunomodulation, 2010; 17: 153-156.
7De Mello Schier AR, et al. “Cannabidiol, a Cannabis sativa constituent, as an anxiolytic drug.” Rev Bras Psiquiatr, 2012; 34; S104-110.
8De Mello Schier AR, et al. “Antidepressant-like and anxiolytic-like effects of cannabidiol: a chemical compound of Cannabis sativa.” CNS Neurol Disord Drug Targets, 2014; 13 (6): 953-960.