Fentanyl analogues in apparent opioid toxicity deaths:

About fentanyl analogues

Fentanyl analogues are a group of synthetic opioids structurally and chemically related to fentanyl, designed to mimic the pharmacological effect of the original drug^{Footnote 1}. Many of these substances are produced illegally, were never tested or approved for human use, and vary widely in potency, toxicity, and onset of action^{Footnote 2Footnote 3}. Since the mid-2010s, fentanyl analogues have appeared intermittently in Canada's unregulated drug supply often replacing or mixed with fentanyl, contributing to changing risks and patterns of substance-related harms^{Footnote 4}. This report focuses on the fentanyl analogues most commonly reported in death investigations and a comparison with drug samples analyzed by the DAS as a proxy measure of the composition of the illegal drug supply in Canada, including carfentanil; acetyl fentanyl; butyryl, isobutyryl, methyl fentanyl; and ortho-, meta-, and para-fluorofentanyl.

Fentanyl, fentanyl analogues and non-fentanyl opioids involved in deaths

Since 2018, fentanyl without fentanyl analogues has been involved in a substantial percentage of apparent opioid toxicity deaths (AOTD) in Canada, from 52% to 77% of AOTDs until 2023, dropping to 41% in 2024. AOTDs involving fentanyl analogues without fentanyl have remained relatively stable since 2018, generally representing less than 10% of deaths, with a brief increase to 13% in 2019. In contrast, the percentage of AOTDs involving the combination of fentanyl and fentanyl analogues has grown in recent years, from 4% of deaths in 2018 to over 30% in 2024.

AOTDs involving non-fentanyl opioids, without fentanyl or fentanyl analogues, have fluctuated over time but generally remain within 12–25% of deaths.

Specific fentanyl analogues involved in deaths

The four most frequently reported fentanyl analogues involved in apparent opioid toxicity deaths (AOTDs) between 2018 and 2024, were carfentanil, acetyl fentanyl, butyryl/isobutyryl/methyl fentanyl, as well as ortho-, meta-, and para-fluorofentanyl.

Carfentanil peaked at 20% of AOTDs in 2019, with subsequent fluctuations and a gradual decline to 3% in 2024.

• Carfentanil was originally used as a veterinary tranquilizer for large animals and is 100 times more potent than fentanyl and 10,000 times more potent than morphine^{Footnote 5}.

Acetyl fentanyl has consistently remained under 5% of deaths.

• Acetyl fentanyl was never approved for therapeutic use. Although it is less potent than fentanyl, it is 15 times more potent than morphine^{Footnote 6Footnote 7}.

Butyryl/isobutyryl/methyl fentanyl was infrequently reported until 2024, when it rose to 11% of deaths, marking a notable increase.

• This analogue has no therapeutic applications, and while it is less potent than fentanyl, butyryl fentanyl it is seven times more potent than morphine^{Footnote 7}.

Ortho-, meta-, or para-fluorofentanyl was minimally involved in AOTDs through 2021 but then increased to 26% in 2023 and 32% in 2024, becoming the fastest-growing analogue in recent years.

• Some research shows that fluorofentanyl has varying degrees of potency depending on the isometric form, with some showing ortho-fluorofentanyl as more potent than fentanyl, para- being equivalent to fentanyl and meta- as less potent^{Footnote 8}.

Fentanyl analogues in Canada's unregulated drug supply

Health Canada's Drug Analysis Service (DAS) examines samples of seized drugs from law enforcement activities to identify contents and provide insight into the substances that may be circulating in Canada's unregulated drug supply; however, these data may not represent the end-products that are ultimately sold or consumed in the unregulated market.

From 2018 to 2022, over 50% of opioid samples seized and examined by DAS contained fentanyl without fentanyl analogues. This percentage declined to 42% in 2023, and 25% in 2024.

The percentage of opioid samples that contain fentanyl and fentanyl analogues have been increasing over time, from approximately 3% to 6% from 2018 to 2022, up to 22% in 2023 and then 24% in 2024.

The percentage of opioid samples that contain fentanyl analogues, without fentanyl, have also increased over time from 1% to 9% from 2018 to 2023, up to 21% in 2024.

The percentage of non-fentanyl opioids, without fentanyl or fentanyl analogues, have remained relatively stable, accounting for 24–30% of samples over time.

In terms of specific categories of fentanyl analogues identified in DAS samples, Carfentanil peaked in 2019 at 10% of opioid samples, declining to 1% in 2024, while para-fluorofentanyl increased substantially, from being undetected in 2018 to being identified in 26% of opioid samples in 2023 and 32% in 2024.

Detection of acetyl fentanyl in opioid samples remained very low during the whole time period.

Butyryl/isobutyryl/methyl fentanyl rose from very low detection in 2018 to being present in 17% of opioid samples in 2024.

Trends in fentanyl and fentanyl analogues in the drug supply and in deaths

Patterns of fentanyl and fentanyl analogues involved in AOTDs generally align with percentage of fentanyl and fentanyl analogues detected in opioid drug samples submitted to DAS by law enforcement; however, differences in timing between drug seizures and mortality data should be considered when interpreting these trends (refer to limitations).

• Fentanyl remains the most commonly reported opioid in drug samples and in AOTDs though its involvement has gradually declined in recent years.
• Fentanyl with fentanyl analogues have risen steadily in drug samples and AOTDs, with percentage increases in the supply slightly outpacing those seen in deaths.

The trends in specific fentanyl analogues were also similar in AOTDs and drug samples:

• Carfentanil was historically the most frequent analogue detected in both drug samples and AOTDs but has declined over time.
• Fluorofentanyl has surged since 2023, becoming one of the most frequently detected fentanyl analogues in both drug samples and AOTDs by 2024.

Implications

The toxic drug crisis is one of the most serious public health crises our country has ever faced. After years of increasing opioid-related toxicity deaths, Canada saw a notable decline in deaths starting in 2024^{Footnote 9}. The findings in this data blog highlight the continued emergence of fentanyl analogues, in combination with fentanyl and alone, in both Canada's unregulated drug supply and apparent opioid toxicity deaths.

Shifts in the toxic drug supply is a likely contributor to the recent decline in opioid-related deaths^{Footnote 10}. However, it's important to note that the drug supply is unpredictable, and it is unknown whether these declines will be sustained.

Limitations

Deaths included in this analysis are limited to records in CCMED where substances were mentioned in the cause of death fields. While we use the term "involved in" to describe these substances, their presence in the cause of death fields indicates they may have contributed to the death. No additional details on toxicology results are available.

Some fentanyl analogues may not be included in routine toxicological analyses in all provinces and territories, depending on the year. Structural isomers (e.g., butyryl/isobutyryl/methyl fentanyl and ortho-/meta-/para-fluorofentanyl) were not consistently distinguished in cause of death statements, as a result, they were combined for this analysis.

CCMED data were available for 11 provinces and territories. Only deaths for which the death investigation was completed were included in this analysis. Quebec data were excluded as their use of ICD-10 codes did not provide sufficient detail for this analysis. Manitoba data are not available in the database. British Columbia data were included, but substance-level information is limited across the analyzed period.

DAS data is based on samples submitted for analysis and may include multiple samples originating from the same seizure or large drug busts. Exercise caution when interpreting the DAS data due to the following:

1. Samples from drug seizures may not represent all drug circulating on the market, all substances seized in Canada, the end-product sold to persons who use drugs, or consumption of substances;
2. Data relies on detection and is not indicative of toxicity/lethality;
3. Multiple samples per seizure may lead to overcounting.

While ortho-, meta-, and para-fluorofentanyl can be identified, only the para-fluorofentanyl isomer has been detected in samples submitted to DAS to date.

Temporal considerations should be noted as substances identified in seized drug samples may circulate in the unregulated drug supply prior to being reflected in AOTDs. Differences in timing should be considered when interpreting year-to-year trends.

Data sources

• Mortality data were obtained death investigation data from the Canadian Coroner and Medical Examiner Database (CCMED). CCMED includes all deaths that are investigated by coroners and medical examiners in Canada. For additional information visit the Canadian Coroner and Medical Examiner Database (CCMED).
• Drug Analysis Service and Cannabis Laboratory. Ottawa: Health Canada; January 2026. Findings presented here may differ from other data from the Health Canada Drug Analysis Service as these data are presented and analyzed in a different manner. For additional information about the work of the Health Canada Drug Analysis Service visit the Drug Analysis Service and Cannabis Laboratory.