Small quantities of drugs are getting past customs and then being used to create much bigger batches of illegal drugs like synthetic heroin.
As Canada moves towards legalization of cannabis in 2018, there is growing evidence of the drug's potential to treat opioid addiction itself, as well as the chronic pain that often drives it.
UK must now respond to arrival of fentanyl, which has for years been a major drug problem in the US and Canada.
Synthetic opiates are a growing problem.
One in five Canadians suffers chronic pain and almost 2,500 died last year from opioid overdose. A National Pain Strategy promises to tackle both problems.
Scientists have never found a medicine to help crack users who want to decrease their consumption. Canadian researchers think cannabis might be the answer.
Carfentanil is an ultra-potent synthetic opioid. Its only legitimate use is in veterinary practice for large animals such as elephants, but it sneaks into heroin shipments to increase its potency.
It is thought that in 2002 fentanyl, or a drug based on fentanyl, was used by Russian special forces to disable Chechen rebels after a four day stand off in the Dubrovka theatre in Moscow.
Prince’s death was recorded as accidental. Accidents are common when it comes fentanyl, a powerful pain killer 100 times stronger than morphine.