Sleeping pills;
This is an important overlooked point.
Tamazepam ( SP ? ) is a cleared, prescription sleeping pill, but very powerful, much in demand by druggies who will beg, borrow or steal it; I'd not have thought safe to fly until long after using, and I think it's addictive ( I have trouble sleeping, am not aircrew, but I doubt I could get it from my doctor even now ).
Diazapam is a weaker pill, more of a calmer-downer than sleeping pill, if having taken a very small dose I would think it OK to fly after a good 10 hours, but still addictive and I expect most Doctors would disagree with it's use entirely when flying.
There are other subtler drugs available, but rule out Nightol, available from chemists - the only version which has an effect on me is the one -shot version, there are also 2-shot and herbal versions which work in incrementally decreasing efficiency and value; after taking one-shot- Nightol, I have definitely found myself feeling sh**ty the next day, and certainly wouldn't want to drive a car, let alone an aeroplane.
Nightnurse, unless it's changed a lot since years ago when I had it, is a very powerful sedative inc' alcohol and should be avoided at all costs - you'd be better off after a sleepless night listening to the radio than flying with that stuff.
Likewise beware Benolyn cough medicicine; it seems to me it only works against coughs in its' original form, the 'non-drowsy' doing bugger all help to cure one's cough if persistent; however 'original' Benylin is also VERY powerful, I'd hate to think of flying within 48 hrs of touching it...
A couple of tricks I have learned in order to get to sleep;
1, And I Know this works - imagine in your mind a route by road you know well, picture in your mind every turn, junction, straight etc - I guarantee you will be snoring before you reach the end.
2, put on your ( personal civvie ) radio, if necessary with earplug' phones so as not to disturb anyone nearby, and tune into the world service / any local radio in the UK; this will put you to sleep, there might be the odd informative bit, but I guarantee you some sleep !
All the best,
DZ