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Dr. Erin Binagia is an adjunct professor at Texas A&M University, a relief criticalist at MissionVet Specialty and Emergency in San Antonio, Texas, and a critical care consultant for Veterinary Specialists on Demand. This month, she answers our questions about her latest study, which looks at data (collected from January 2017 to July 2021) from 223 dogs with a history of marijuana ingestion or a positive tetrahydrocannabinol result from a human urine multidrug test. You can find the full text in the August print issue of JAVMA.
Do you have any pointers for primary care veterinarians on how to handle cases of suspected canine marijuana toxicosis?
Dr. Binagia: Personally, I recommend using the human urine multidrug test (HUMT). The HUMT used in this study worked very well compared to previously reported studies. A positive HUMT can confirm marijuana toxicity. But remember, a negative HUMT does not rule out the possibility of marijuana exposure. That needs to be communicated to the client as well.
Remind the client that it is OK to admit that their dog may have been exposed to marijuana. After all, marijuana toxicosis has a much better prognosis than other illnesses and diseases with similar acute neurologic signs.
In this study, the survival rate was 100%; clinical signs resolved within 12 to 24 hours with no treatment in most cases. Otherwise, common treatments include fluid therapy (marijuana is excreted through the kidneys) and antiemetics. Because marijuana is highly lipophilic, intravenous lipid therapy is a treatment option for severe cases. Any concerning cases can be referred to a criticalist.
What is the most important takeaway from this study?
Dr. Binagia: A common presentation of marijuana toxicosis is a young dog with a combination of acute ataxia and hyperesthesia with or without urine incontinence with normal vitals and bloodwork. However, in patients with abnormal vitals and bloodwork, common findings were hyperthermia, tachycardia, hypertension, mild hyperkalemia, and mild ionized hypercalcemia. The presence of hyperkalemia and/or mild ionized hypercalcemia may increase the index of suspicion of marijuana intoxication. When interpreted as directed by the package instructions, sensitivity of the HUMT in dogs is low. Marijuana should be high on the differential list with these physical exam, neurologic exam, and clinicopathologic findings regardless of a negative HUMT or a client’s denial of marijuana exposure.
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Is there a specific clinical examination finding or electrolyte abnormality in dogs with marijuana toxicosis that you found most surprising?
Dr. Binagia: The most surprising finding to me was that about 80% of the 67 cases that had an ionized calcium measured had an ionized hypercalcemia. My initial research revealed that is a transient occurrence in acute toxicoses reported in humans and rats. With further research, I found that heavy, chronic use of marijuana may be associated with poor bone health in humans. I believe that ionized hypercalcemia may be a better biomarker for marijuana toxicity in dogs than hyperkalemia.
The other finding that surprised me was that when a dog’s vitals were abnormal, tachycardia (37%), hyperthermia (23%), and hypertension (61%) were much more common than bradycardia, hypothermia, and hypotension, as many veterinarians may presume. Yet those clinical findings are dose-dependent, and higher doses of marijuana lead to bradycardia, hypothermia, and hypotension.
Did the study’s findings align with your predictions based on your emergency and critical care experience?
Dr. Binagia: Overall, yes. I predicted that mild hyperkalemia would be common, as well as ataxia, hyperesthesia, urinary incontinence, lethargy, and vomiting, which were found to be the top 5 clinical findings in this study (in that order). Also, the most common combinations of neurologic signs included ataxia and hyperesthesia (70%) and ataxia, hyperesthesia, and urinary incontinence (36%).
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Is there anything else you would like our readers to learn or know from your study?
Dr. Binagia: A common history was that the patient became acutely neurologically abnormal after going outside or to a public place (28%). Other common histories included the patient becoming neurologically abnormal after having visitors or visiting others (9%), waking up (5%), being home alone (4%), or being released from their crate (3%). Those common histories may encourage you to consider marijuana toxicosis as a differential diagnosis.
The HUMT instructions state that “all faint lines, including barely visible ones, should be interpreted as negative.” However, that recommendation is based on the suggested screening cut-off for positive human samples (set by the Substance Abuse and Mental Health Services). However, dogs produce much less of the measured metabolite in urine. Meaning, that cut-off should be lower in our canine patients. Perhaps a faint line, or “slight positive,” should be acceptable to confirm intoxication. Further research is needed to determine if a faint line/slight positive on HUMT should be considered a positive result.
The Study:
Clinical examination findings and electrolyte abnormalities of dogs with marijuana/tetrahydrocannabinol toxicity: 223 cases (January 2017-July 2021).
Binagia EM, Gregory EA, Yankin I. JAVMA. doi.org/10.2460/javma.24.02.0092