February 27, 2015
As many states move to legalize or decriminalize medical and recreational marijuana use, more pets may be exposed to marijuana smoke and edible products as their human owners increasingly gain legal access.
According to the public information non-profit ProCon.org, which has created a chart of medical marijuana laws state-by-state, medical marijuana is now legal in 23 states and Washington, D.C. This November, Oregon, Alaska and Washington, D.C. joined Colorado and Washington State when ballot measures passed to allow the sale and use of recreational marijuana.
Veterinarians in these states which have recently voted to legalize are looking to the examples of Washington and Colorado for what to expect. A 2012 study published in the Journal of Veterinary Emergency and Critical care looked at the increase in reports of marijuana toxicity in dogs at two Colorado hospitals in five years following the legalization of medical marijuana in that state. The study found the number of marijuana poisoning cases in dogs at two Colorado veterinary hospitals quadrupled during the 5-year period. This correlated with a 146-fold increase in the registration of people with medical marijuana cards. Two of the dogs, which had ingested baked products made with medical grade tetrahydrocannabinol (THC) incorporated into the butter, actually died. The study examined the period between January 1, 2005 and October 1, 2010, so it did not address any increase resulting from the legalization of medical marijuana in 2012.
Some ingestion of marijuana by pets occurs by accident, through exposure to second-hand smoke or when a pet raids its owner’s unattended stash of marijuana or edible products. Exposure to marijuana is rarely fatal in dogs, as the minimum lethal oral dose for THC is more than 3 g/kg, which is more than 1000 times the dosage where the owner can begin to notice behavioral symptoms. Although this gives the drug a high margin of safety, medical-grade THC butter is more concentrated, which is probably what proved fatal for the dogs in the Colorado study.
Colorado’s long history with medical and recreational marijuana has enabled veterinary medical researchers in that state, Kevin T. Fitzgerald, PhD, DVM, DABVPa,n, Alvin C. Bronstein, MD, FACEPb, and Kristin L. Newquist, BS, AAS, CVa, to compile a Topical Review of Marijuana Poisoning; its effects and its treatment.
According to this review, observable effects begin within an hour of ingestion and could range for up to 1 to 3 days, although 24 hours was the average duration of symptoms. Recovery can take as long as five days, however, in cases of exposure to a very high dose.
Dogs presented with a wide range of symptoms, including depression, hypersalivation, dilation of the pupils, loss of muscle coordination, vomiting, urinary incontinence, tremors, hypothermia, and bradycardia. Higher dosages may additionally cause involuntary eye movements, agitation, rapid breathing, tachycardia, hypotension, ataxia, hyperexcitability, vocalizations and seizures. Dogs may be sensitive to motion, light and sound. Although some cardiovascular symptoms may be observed, particularly at higher doses, exposure does not result in long-term cardiovascular effects.
The veterinarian must continually monitor body temperature, heart rate and rhythm during the course of therapy. Typically, supportive therapy is sufficient and vomiting can be induced if ingestion is recent. However, Fitzgerald et al. observe that since THC has been shown to suppress nausea and vomiting, efforts to induce may not be effective unless ingestion is recent (within the past 2 hours). The animal’s respiration must also be monitored closely as marijuana poisoning can cause respiratory depression.
Oregon veterinarians are bracing for an increase in marijuana-related cases. The state voted to legalize recreational marijuana in November 2014. As of July 1, 2015, possession by individuals over 21 of up to 8 ounces of marijuana and four plants per residence will become legal in the state. As in Colorado, Ore. vets have also noticed an increase in marijuana pet overdose incidents correlating to pet owners’ access to medical marijuana. Cassee Terry, DVM, of Redmond, Oregon recounts an emergency call she received for a Labrador cross that was behaving strangely. The owners thought she may have been hit by a car.
“She presented with lateral recumbent, nonresponsive, stiff front legs,” Terry said. “I suspected back trauma but she wasn’t in shock … nice red membranes, strong heart rate, etc. We took radiographs and her back looked great.” Then Terry noticed the dog’s stomach seemed very large. She asked the owners to try to think of possible toxins the dog may have eaten. They reported they were licensed medical marijuana growers and had just finished preparing a batch of THC-infused butter for a client with cancer. Terry induced vomiting and “sure enough all the discarded pot plant material came out … she should have been fine and should sleep it off,” but unfortunately the owners did not return the follow-up calls to confirm the dog’s recovery.
Curt Nitschelm, DVM, also of Redmond, Ore., notes that “these cases will definitely increase with all the edible options that dogs love.” He recalled the case of a Great Dane who found “doughnuts covered with marijuana butter.” Dogs are already attracted to the leaves and stems of the cannabis plant itself, as Terry observed. However, as growers regularly combine TCH oil with butter and then bake it into products such as cookies and brownies, sometimes containing high amounts of sugar and even chocolates, so-called edibles are very attractive to dogs. If dogs, particularly small dogs, consume baked good prepared with THC butter and baking chocolate, which is also poisonous to dogs, but presents with different symptoms, this can also complicate accurate diagnosis and treatment.
Veterinarians will not only continue to be faced with the medical implications of marijuana toxicity in their patients, but will also continue to struggle with the ethical challenges that marijuana can pose for medical professionals. In states where marijuana possession or use may be illegal, veterinarians will already be battling against pet owners’ fears of prosecution in the event that their pets accidentally gain access to marijuana products. As Fitzgerald et al. advise, “Nowhere is there a greater potential for an untruthful history as in the case of an animal’s ingestion of an illicit drug. Veterinary clinicians must gain the confidence of the client quickly so as to obtain a valid history.”
At the same time, veterinarians must also recognize that human use of marijuana might reduce good judgment in pet owners and could lead them to deliberately expose their pets to smoke, bong water or other cannabis products. This is a different ethical issue than accidental exposure.
Pet owners could be concerned about being turned into authorities, as some people who intentionally expose their pets to this drug have been prosecuted. On one hand, veterinarians and staff must establish an environment of trust in which pet owners feel they can honestly relate what their pet may have consumed in order to facilitate the delivery of life-saving treatment. On the other hand, vets need to balance this need for trust against their duty to protect their patients, and the obligations to report animal abuse or neglect. Twenty-nine states have laws either requiring or permitting veterinarians to report animal neglect, cruelty, or abuse to authorities.
Perhaps the next ethical frontier for veterinarians regarding broadening marijuana use is the debate over medical use for pets. Pet owners using marijuana for medical purposes may approach veterinarians about the possibility of treating similar conditions — such as pain, seizures, and cancers — in their pets. This 2013 article on the American Veterinary Medical Association website explores the medical marijuana debate in veterinary circles and attempts to prompt veterinarians to consider the implications.
Besides the legal obstacles, there are ethical and medical difficulties in responsibly recommending marijuana for medical use in pets. Although some speculate that recent comments by the newly appointed Surgeon General, Dr. Vivek Murthy, signal changes on the horizon, marijuana is currently classified as a Schedule I narcotic, meaning it is considered highly addictive with no federally recognized medical benefits. Due to this classification, there are numerous bureaucratic obstacles to obtaining it legally for purposes of scientific research. As a result, there is not solid scientific evidence that marijuana is efficacious in treating specific conditions in animals. There is also no proven safety data or specific information regarding dosing. Although companies are producing and selling cannabis products marketed to pets, and some veterinarians and alternative practices are prescribing them to their patients, no federal or medical body regulates the industry’s manufacturing process so pet owners must take the company’s word that the capsules contain the promised contents, dosages and concentrations.
Rescheduling marijuana could allow researchers easier access for human and animal medical studies. However, until such studies are completed; until the drug is approved for safe and effective use in animals; and until the manufacture of medical marijuana for animals is comprehensively regulated; use of marijuana to treat medical conditions in pets will continue to take place based on off-label prescriptions or by owners administering the drug to their pets independently. Vets should therefore be prepared for possible overdoses, contamination during manufacturing and other potential consequences.
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