Nitrazepam is an excellent hypnotic. It is highly sedative, muscle relaxing, and yes it can "knock you out" if you aren't very tolerant to benzos. Out of all the benzos I've tried (and I've tried many, many benzos) triazolam is the most sedative and nitrazepam is second most sedative. I compare it most to temazepam and flunitrazepam, only a bit more sedative than both. It does have a long half-life, so expect a hangover effect the next day (it lingers on all day, causing grogginess, fatigue, and sleepiness). Studies have shown that nitrazepam builds tolerance relatively quickly and usually by the 4th to 6th date the effect of a particular dose begins to wear off.
If you don't have a benzo tolerance then 10 mg is enough to get you to sleep, 20 mg would be the recreational dose for someone who isn't benzo tolerant.
Mostly agree with the above. It is the most hypnotic and sedating benzo I have tried, on a list that includes midazolam, temazepam, flurazepam, lormetazepam and etizolam - to list some of the other hypnotics I've had.
However, I would say that for a person without benzo tolerance, 5mg should be plenty to get to sleep. I consider myself to have above-average natural resistance/tolerance to benzos if I don't have any in my system, or so I have ascertained from other people's dosages, and I switched from 40mg temazepam to 5mg nitrazepam (the former did not guarantee sleep - the latter, initially, did). I try to take hypnotics on 2-3 consecutive days tops, and then take a night without (or two if possible), to avoid tolerance buildup. In this way, 5mg had me sleeping like a baby for well over a week, and 10mg was enough for about another week, when I felt my psychological problems were subsiding and I began a very quick taper down. I may be an oddball, though, since I consider temazepam pretty average (better than a lot, but not among the best) and nitrazepam one of my favourites both in terms of therapeutic use as a hypnotic and recreational use. Maybe I'm somehow sensitive to nitrobenzodiazepines; clonazepam is also hugely effective for me.
If you have no tolerance, it may or may not "knock you out" - 10mg certainly may, and if you go to bed and lie down, it should definitely happen (hypnotics aren't, after all, meant to make you pass out on your couch before you actually go to bed), even with 5mg. The half-life was something like 15-40 hours and while this doesn't always correspond with actual effects, I have always felt quite a strong residual sedation or 'hangover effect' from nitrazepam. It is dose-dependent, but usually I consider the full effects of nitrazepam to be around 12-14 hours - ie. I will still be noticeably groggy and impaired both physically and mentally 12 hours after taking the drug (whereas with eg. diazepam, the full effects - unless doses are very high - subside around 5-8 hours).
