ב''ה,
If I can spare any misery, the days of fatal sleeping pills were the barbiturate era and whatever vaguely related sorts of substances preceded that. These are basically no longer a thing, or at minimum very medically controlled and limited to unique neurological conditions as far as USA goes. Don't particularly know details on what would be required but 'those were the days.'
What is commonly available OTC in USA is, aside from melatonin, either straight up Benadryl (some varieties of Unisom) or doxylamine, the sedative antihistamine in NyQuil, sold as the original Unisom.
In ordinary amounts those cause drowsiness and work as sleep aids, and doxylamine in ordinary amounts is quite pleasant for benzodiazepine withdrawal symptoms if that news makes it to whoever in another thread was up against that.
In excess, these are only going to do you delirium and brain damage. While once popular enough among the 'nothing to do but abuse OTC medication' teenaged set, this is not fun and the lasting symptoms will at least leave you swearing you have brain damage. If you're just trying to sleep or have an evening let's say there's no point in going beyond two of the slightly more pleasant doxylamine tablets when the box says only one.
Anyway, the other OTC stuff will be melatonin, as also doesn't do anything particularly lethal in massive amounts, but feels disgusting in excess although some claim to enjoy it. You know the feeling of when your body has lost all track of time in a windowless room, or the sensation of being on your third wind after an all nighter? How many days would you like to experience that? Also may trigger acne.
Occasionally there will be non-melatonin herbs that are generally notionally soothing things like lavender or chamomile, basically food items.
Prescription sleep medicines these days are mostly 'melatonin but prescription so your insurance pays for it,' Valium but in a different class of chemicals so they could pretend it wasn't (Ambien and relatives), actual Valium/other benzodiazepines, and whatever that newish GHB one is.
You can quite readily 'roofie' yourself with these and have Ambien stories etc., but physical toxic harm is, let's say low in the sense that they tend to stop selling things if people who choose to eat the whole bottle die.
Meanwhile, anyone around for the 1990s knows that a few people managed to have fatal or coma issues with GHB, possibly combined with binge drinking levels of alcohol, but also that half the college dorm was living that life and whatever specifically caused the long comas or deaths remains a matter of discussion as far as I know; so 'potentially risky' as in don't binge drink with the stuff if not up for 'CTB,' yet not really a sure thing at all.
While I won't make odds on this to understand the general principles: you would be much more likely to be permanently injured from any of the stupid things you might do on large amounts of these substances before passing out for a day's nap than by the substance itself in obtainable quantities, barring an allergy, unique medical condition or really bad luck (such as choking on your vomit while knocked out).
Similarly, while serotonin syndrome is a thing, the modern class of antidepressants.. don't do this because it is miserable for various other reasons, but while not necessarily "safe" in massive amounts are generally selected for "eating the whole bottle does not kill people" for the industry's convenience.
