Trends in opioid containing drug seizures described as pills between 2020 and 2024 in Canada

People who use drugs may access prescription opioids from unregulated markets to avoid fentanyl and lower toxicity risk, though concerns regarding counterfeit pills have emerged. To better understand the composition of pills that may be circulating in the unregulated drug supply, we described trends in the composition of law enforcement seizures of opioid-containing pills across Canada. We conducted a repeated cross-sectional analysis of opioid containing drug samples described as pills, seized by law enforcement and analyzed by Health Canada’s Drug Analysis Service between February 1, 2020, and December 31, 2024. We reported the proportion of samples containing at least one of the following opioid subclasses: morphine, hydromorphone, codeine, oxycodone, buprenorphine, methadone, fentanyl/analogues, or nitazenes. All analyses were reported overall and stratified by year the sample was submitted for analysis. We identified 24,045 opioid-containing samples described as pills across Canada. Oxycodone was detected in 35.6% (N = 8,570) of included samples, while hydromorphone was present in 28.2% (N = 6,792) of samples. Prevalence of oxycodone (N = 1,493 [40.0%] in 2020 to N = 1,882 [35.6%] in 2024) and hydromorphone (N = 711 [19.0%] in 2020 to N = 2,016 [38.1%] in 2024) containing pills fluctuated overtime. Less than 10% of samples contained fentanyl between 2020 (8.8%; N = 327) and 2022 (5.0%; N = 224), then a sharp increase was noted in 2023 (23.9%; N = 1,410). However, the high prevalence of fentanyl-containing pill samples was not sustained, declining to 3.3% (N = 173) in 2024. The presence of counterfeit fentanyl-containing pills within the unregulated drug supply poses a public health threat, particularly for those seeking pharmaceutical-grade opioids as a method of harm reduction. Diverted pills may be sought to avoid fentanyl exposure and reduce toxicity risks. Pills containing Oxycodone were most commonly seized by law enforcement, followed by hydromorphone. Majority of fentanyl-containing pills seized by law enforcement included another substance, such as benzodiazepines. Improved access to drug checking services, patient-centred treatment and alternatives to the unregulated drug supply is warranted.