Illicit drug overdoses are rising in northern British Columbia and health officials warn a new mix of street drugs can make a key life-saving medication less effective.

Northern Health and the First Nations Health Authority have issued an overdose alert, warning that benzodiazepines, or benzos, have been found in illicit drugs circulating in the region.

The alert says users of drugs contaminated with benzos might be difficult to rouse and could also be slow to respond to naloxone, the drug that reverses opioid overdoses.

Health officials say benzos impede brain activity and raise the potential for overdose when mixed with street drugs laced with opioids such as fentanyl, which slow breathing and heart rate.

The health authorities say street drugs have become increasingly toxic and unpredictable during the COVID-19 pandemic and they urge area drug users not to use alone.

Data from BC Emergency Health Services shows overdoses spiked in northern B.C. between 2019 and last year, with calls in Fort St. John rising from 77 to 125, while paramedics in Prince George answered 999 overdose calls in 2020, an jump of 375 cases in one year.