Actor Heath Ledger’s father, Kim Ledger, has spoken about the tragic death of his son in 2008 from a drug overdose.

The night before his death, Ledger’s sister Kate had warned him against mixing prescription medications.

In an interview with news.com.au, Kim Ledger said, “The last conversation Kate had with him was this discussion about his medications and she warned him, ‘‘You can’t mix drugs that you don’t know anything about’.”

“He said ‘Katie, Katie, I’ll be fine’. Well, that’s a cavalier boy’s answer. It just put his whole system to sleep I guess.”

Ledger died at the age of 28 in his New York apartment from a combination of several different prescription medications.

A toxicology report found that Ledger’s death was the result of “acute intoxication by the combined effects of oxycodone, hydrocodone, diazepam, temazepam, alprazolam and doxylamine” and was deemed an “accident, resulting from the abuse of prescribed medications.”

Australia ranks highly in terms of recreational drug use according to the United Nations 2014 World Drug Report.

The country ranks first for ecstasy, second for opioids, third for methamphetamines, fourth for cocaine, and seventh for cannabis.

In the eight years since his son’s death, Kim Ledger has been working to raise awareness about prescription medication misuse.

Kim Ledger stated that his son was not addicted to opioids but had simply made the mistake of mixing the wrong drugs.

He said, “It was a one-off thing. That’s what killed us, because he was warned by his sister the night before: ‘You shouldn’t mix what you’re taking for pneumonia with your ambien’. But most of Heath’s problems were self-induced.”

He went on to say that his son’s hectic work schedule had begun to take its toll. “There is pressure on everybody, especially young people, to perform and to keep going.”

“He was a young guy that travelled all the time for work. Even as a two-year-old, he hardly ever slept. He was trying to work and travel and do everything in a short space of time.”

Kim Ledger believes that most Australians are unaware of the extent of the opioid abuse problem in the country.

He said, “(Australians) are definitely not up to speed with just how bad these things can be. Heath mixed a couple of drugs together with sleeping tablets and he’s gone forever. That’s something we (himself, wife Sally and sister Kate) just have to deal with.”

Addiction medicine specialist Dr Christian Rowan states that Australia’s prescription drug addiction problem is one of the biggest in the world.

He said, “450 Australians die as a result of prescription opioid misuse every year.”

A survey by ScriptWise, an organization trying to prevent prescription medication misuse, found that a quarter of Australians admit to using opioid painkillers every month, but almost half were unaware of their addictive nature.