Between February 2019 and March 2020, 56 dogs were enrolled in the study. The amount of Δ9- tetrohydrocannabinol (THC) ingested was available for eight dogs (14%). The average dose ingested for those dogs was 175 mg (range 35-4,400). Types of sources reported included both commercial and homemade edible products (15), marijuana plant material (3), and commercial THC concentrate (1). The time since ingestion to arrival at the hospital was known for 12 dogs, with a median presentation time of two hours and a range of forty minutes to six hours.
Similar to previous reports, the most common clinical signs included an inappropriate level of alertness, poorly coordinated gait, and exaggerated responses to visual and auditory stimuli. Of the 56 dogs enrolled in the study, 55 (98%) tested positive for THC in plasma by liquid chromatography/mass spectrometry. Eighteen dogs (32%) tested positive using the Alere drug screening test and 26 dogs (46%) tested positive using the Narcocheck drug screening test. All animals that tested positive using the Alere test also tested positive on the Narcocheck test. Calculation of sensitivity for both the Alere and Narcocheck drug screening tests was performed on the 55 dogs testing positive via LC-MS demonstrating values of 33% and 47% respectively.
This study highlights the shortcomings of point of care urine drug screening systems in the diagnosis of acute THC exposure in dogs. Potential causes for a low sensitivity may include timing, the substances the screening test identify in the urine, and patient factors including level of hydration and urine concentrating ability. This study does support the use of history and clinical examination in identifying animals with THC exposure. Future analyses of THC substances in dog urine may provide a more ideal point of care diagnostic test that targets metabolites that concentrate in dog urine following acute THC intoxication.
