But her world came crashing down when, rather than her son on the line wishing her a merry Christmas, it was one of his friends telling her he was dead.

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“He was a lovely, fun-loving, very generous man,” Sally recalls. “He went to bed and went to sleep and never woke up.”

It took 18 months before Sally, from Sydney, discovered that the drugs valium and oxycodone, which he had been prescribed by his GP, had killed him.

Daniel is one of the thousands of Australians killed by prescription drugs in the past few years in an epidemic that shows no sign of abating.

Opioids and benzodiazepines depress the central nervous system and breathing and when used separately or together, especially with alcohol, can be fatal.

Aussie actor Heath Ledger died in New York from an accidental overdose from a cocktail prescription opioids, while the singer Prince died from using fentanyl.

Daniel had struggled with alcohol dependence and was given valium for anxiety when he had stopped drinking. He was later given oxycodone for pancreatitis.

“He had sub-therapeutic levels in his blood — lower than the recommended dose, but there is a massive risk of a multiplier effect when the drugs work together,” Sally says.

“People don’t realise the massive risk of dying if you combine these drugs.

“Nobody ever expects to lose a child and the devastation is unimaginable. Losing a child, well, it doesn’t get any worse. You never get over it.

“We still have ‘white coat syndrome’ where we do not like to ask questions of doctors because we are conditioned to think what they are telling us is correct.

“I can’t change what happened but I can hope, perhaps, to prevent somebody else suffering the same fate as my son.

“It needs to be more supervised and more diligently monitored.”

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‘It was so easy to get these drugs’

It took Sally so long to receive the toxicology report on Daniel’s death because of a backlog caused by the vast number of unexplained accidental overdoses in Canada­.

For Colleen Davison, from Horsfield Bay on NSW’s Central Coast, her story so nearly could have mirrored Sally’s.

Her son Rorke, 30, was prescribed oxycodone after he injured his knee skiing — and within weeks he was hooked.

“One day he rang me and said: ‘Mum, I think I’m in trouble’, so we went down (to Sydney). He was unrecognisable. It was shocking,” she says.

“I couldn’t recognise my own son — I couldn’t get my head around who I was looking at. He had lost all the appearance of the person I knew and loved. He looked like he had been in a bomb blast. We stood there dumbfounded.

“He’s a big boy, over 6ft tall, very strong and skilled in every sport — ice hockey, sailing, tennis. He had lost all his physical strength, his beautiful character.

“He was someone people gravitated to — that was all gone. He was a shadow of his former self. I couldn’t believe it.

“He was taking a serious, life-threatening amount of pills — 60 a day. I don’t know how he survived.”

After four month-long stints in hospitals, his journey back to health has been long and arduous.

Rorke also became dependent on the methadone given to him to wean him from the oxycodone and then to subsequent drugs used to break his dependency.

“It has been horrific,” Colleen says. “He was a child who had never smoked marijuana — I had educated my children about the horror of drug abuse and he had never given me a day’s trouble all his life.

“It never occurred to him that something a doctor prescribed could harm him. It has robbed us all of the last five years.

“It’s so cruel to watch your child go through this. Without the support and love of all his family and friends he would be dead by now. The stress and the worry of it is terrible. It robs you of all the joy of being a normal, happy family.”

Colleen believes that people simply do not understand the dangers of opioids.

“We need to educate people about how dangerous they are,” she says.

“I’m really lucky, but there are so many people out there who aren’t.”