The Dutch euthanasia guidelines and Philip Nitschke (PPH) advise against using opioids because of their unpredictable effects, but they are still used for self-euthanasia.
According to Dutch psychiatrist and suicide researcher Boudewijn Chabot over 50 cases have been reported in The Netherlands where 1 gram of oxycodone was used for ending life, and all of these people died.
One case failed because the person used OxyContin instead of oxycodone or OxyNorm. OxyContin releases the drug slowly, so there was no respiratory arrest.
Opioids can make you sleepy, but they don't cause 48 hours of deep sleep.
That's why a long-acting sedative is needed to prevent waking up from respiratory arrest (preferably 500 mg diazepam or flurazepam).
When someone has significant opioid tolerance, a dose of 1 grams of oxycodone might be too low.