Sounds like you were lucky, that very deep sleep-state near waking, being the clue to a better quality of sleep perhaps.
Zolpidem. I'm worried now.
Some time ago I mentioned that I felt this 'Hypnotic' type sleeper might be good for aircrew. Not approved yet, but used by American military crews as an after-flight remedy. Very, very fast, and for me at least, no effects that I could detect upon waking. It was that high speed that gave the problems.
It seems that Zolpidem - trade name Ambien in the US, has been used for 'Date rape.' Two minute white powder tablets and within15 mins, the victim was 'out of it'.
I've yet to talk to the manufacturers, but having used it for years because of back problems, living in two countries and other age-related insomnia, I'm now finding it's very much slower in kicking in, and what's more important, it lingers much longer.
A recent study has shown that people using 'sleepers' in the Hypnotic category, and specifically Zolpidem, are 2 to 3 times as likely to have a car accident the next day. This makes it as bad as Ambien CR (controlled release) which is designed to last all night.
Could this be because they have slowed down the timing of the drug?
Wikki has a lot to say about it, and I feel that it's a shame if the 15 mins and 2 - 3 hours half-life tablets become unavailable because of the misuse.
Zolpidem - Wikipedia, the free encyclopedia