New Alberta study examines drug poisoning cases involving fentanyl and benzodiazepines

An Alberta doctor who specializes in addiction says a forthcoming study based on data from the Office of the Chief Medical Examiner (OCME) is "eye-opening" and underscores the role fentanyl is playing in the province's illicit drug supply.

The study, which will appear in the journal Forensic Science International's September issue and was published online in July, looked at concentrations of fentanyl and benzodiazepine drugs in the blood of people who died of fentanyl toxicity over the last three years.

Advocates and experts have been sounding the alarm about the combination of fentanyl and benzodiazepines, known as "benzo-dope." Health Canada says mixing benzodiazepines with other depressants like alcohol or opioids can be dangerous and increase the risk of overdose. 

The combination has become increasingly prevalent in Alberta and other provinces in recent years. The study says that between 2020 to 2022, the OCME reported 2,812 fentanyl cases, of which approximately 45 per cent had at least one benzodiazepine drug.

The study found that the concentration of fentanyl in benzo-dope cases was considerably higher than in cases where no benzodiazepine drug was detected. The study suggests fentanyl toxicity is the primary cause of death in most benzo-dope cases, not the combination of those drugs. 

"The concerns of the increased dangers associated with the local drug supply in Alberta may be related to an increase in fentanyl concentration, rather than the addition of the benzodiazepine," the paper says. 

Dr. Monty Ghosh, an assistant professor at the University of Alberta and the University of Calgary and an addiction medicine physician, said the study is "eye-opening."

"We always thought that the mix of benzos with the illicit drug supply was making it harder for us to reverse these overdoses," he said. 

He said this data shows that the concentration of benzodiazepines seemed to be too low to have caused respiratory depression (slower breathing).

He said people who are using benzodiazepines may be requiring higher amounts of fentanyl to feel the same euphoria.

"There are a lot of people who are now addicted and suffering withdrawal from benzodiazepines and therefore are at a higher risk of being in a situation where they have to consume drugs more quickly, less carefully, with maybe less stringency around their supply," said Euan Thomson, an independent researcher who writes the Drug Data Decoded newsletter.

Thomson advocates for regulating the supply of drugs, so people know what's in the substances they are using.

Dr. Craig Chatterton, chief toxicologist at the chief medical examiner's office and the lead author of the study, said the research was intended to provide scientific information for people in the toxicology and medical examiner communities. 

"I would not expect the public to draw conclusions, scientific or otherwise, from this study," he said in an email to CBC News.