Montreal health workers are battling an influx of fatal drug overdoses.

They're warning street drug users to lower their doses and be extra vigilant.

In the last month, 15 people have died of drug overdoses — including six people in the last week alone.

Officials who are investigating the increase in deaths said many factors are at play. One of the possible causes could be that the drugs are being 'cut' — or diluted —with fentanyl.

Fentanyl is an anesthetic meant to treat chronic pain. In high concentrations it could stop a person from breathing.

A derivative of the drug, desmethyl fentanyl, is chemically modified to be even more potent — it’s considered to be 40 times stronger than heroin.

Fentanyl made its first appearance on Montreal’s black market last spring.

Health officials said they are warning drug-users to lower their doses and to inject them slowly.

Experts say one of the challenges in preventing overdoses is that most addicts only have one goal — finding their next hit.

“One case in point is of an individual that is in our facility ... When they went to use the drug, there was a funny colour to it, but they went ahead and injected it regardless,” said George Goldberger, the executive director of  Foundation Centre of Addington House,  a drug and alcohol rehabilitation centre in Montreal.

Goldberger said drug addicts are seldom concerned about their safety.

"The heroin user  he's not afraid of dying. He's really not afraid of dying."

Safe injection sites

With the spike in fatal overdoses, Montreal public health officials are calling on the province to approve safe injection sites. 

Richard Massé public health Montreal

Richard Massé, the director of Montreal's public health agency, says having supervised injection sites could have contributed to preventing these deaths. (Radio-Canada)

“Safe injection sites are really part of the solution. Nurses in the safe injection sites are really aware of overdoses. They can intervene very rapidly,” said Richard Massé, director of the Montreal public health agency.

Massé asked the provincial government for four Montreal injection centres last winter, but he said so far he has yet to receive a firm answer.

Massé said the agency is working with the new Liberal government to try to make that happen.