This goes on all the time. I don’t know the specific dosages etc.. but from what I understand, hospitals and hospices easing the process of death not just by alleviating pain but also by actually speeding it up by high dosages of painkillers (and by withholding food, water and antibiotics) is nearly universal. And it goes on in “Catholic” hospitals despite the withholding of those essentials being clearly contrary to Catholic teaching.
I have never seen an excessive dose given and would not tolerate it if it was. Food and water are always available but patients may not be able to take much in due to their condition drugs given to relieve pain and anxiety are a blessing but a lethal dose just for the sake of a lethal dose is a step too far.