LONDON, ON - A rash of overdoses, one of them fatal, has hit Sarnia, ON, as drug addicts turn from banned OxyContin to potentially deadly fentanyl patches, police say.

A woman in her 40s died in June after overdosing on the drug, police in the southern Ontario city said Wednesday.

On June 27, a 17-year-old girl fell unconscious after smoking a fentanyl patch. She was treated in hospital.

On June 28, a 19-year-old man had to be taken to hospital after smoking a patch and falling unconscious.

On July 3, Sarnia police seized six fentanyl patches and more than five grams of methamphetamine from a car, leading to charges against three people.

Police and addiction counsellors predicted people would turn to other drugs once OxyContin was taken off the market in March.

Fentanyl is a particularly dangerous drug to abuse, police say. It's sold as a slow-release painkiller in a skin patch.

Diverted to the street, the patches are chewed or broken down so the gel can be injected, snorted or smoked.

"If one withdraws the 72 hours' worth of drug and uses it in a form that it wasn't designed to be used for, it can rapidly result in death," police said in a news release.

A 100-microgram of fentanyl is equal to 200 milligrams of OxyContin or 400 milligrams of morphine, police said.

Half of a 50-microgram patch of fentanyl could cost approximately $130, police said.

A 100-microgram patch of fentanyl may cost about $300.