This is a tricky topic, and a valid one.
I like to make a distinction between euthanasia and suicide, thinking of them as opposite ends of a spectrum. The furthest end of the euthanasia spectrum is exemplified by person in full command of their faculties and in love with life, untroubled by physical discomfort, financial pressure, or depression, fully supported by a loving and wise family, making an unquestionably logical choice in the face of some unstoppable medical disaster. The end of the suicide spectrum is represented a person who is driven by discomfort, haunted by anxieties that seem out of control, depressed, hopeless, and alone.
The correct way to address a genuine need for euthanasia is to provide a dignified and comfortable death. The correct way to address the suicidal impulse is to provide support - fixing what can be fixed, and restoring the emotional strength necessary to gracefully accept what's left.
In real life everybody is somewhere in the middle. It can be very hard to distinguish a recoverable situation from an unrecoverable one, especially when one is alone. Depression, almost by definition, is a disease characterized by inappropriate and compelling hopelessness, and anyone who's life has grown within sight of the point where euthanasia seems a sensible option, is almost always a person who is also feeling powerless and afraid.
That said, I think there is a healthy and sensible role for euthanasia for folks like us. Having the means to end our lives in some acceptable way means freedom for the very real fear of being trapped by our illness and our circumstances. The flip side of this is that it also makes it easier for a bout of depression and fear to become fatal. It's a tradeoff, and it has to be a tradeoff that each of us decides for ourselves.
The very bottom line for most of us, regardless of our circumstances, is that we can simply choose not to eat or drink. Here in the US, advanced directive can be written to assure this (
http://liv-will1.uslivingwillregistry.com/individuals.html). It's hardly an ideal method of course, but it is not so bad, and it can be comforting to know that this is the worst-case scenario. (I do not know for sure how this would play out in other countries, and how much influence other people - family, or health care staff - would have).
Other methods are available as well, but each carries some risk. It's the sort of thing that's hard to fully test in advance. Drugs can expire, or not be quite as potent as claimed; they might be absorbed too slowly or vomited up. Nitrogen hypoxia requires the technical knowledge to provide a steady, correct flow, over the correct time, and any hypoxic method requires that no fresh air leaks into the confined space if the unconscious body thrashes around. Almost any method might require the ability to get out of bed, or to depend upon a helper. It gets complicated and it can be hard to find reliable help. Mitigating and accepting these risks is, once again, an individual decision.
Detailed discussion of methods invites moral, and possibly legal, hazards. This leaves us with a difficult problem and a minimum of clear answers.