Thanks for the info.
magnesium oxide does seem to relax my muscles -I have tried melatonin alone and it does not have this effect. Infact sometimes I only need the magnesium and forgo the melatonin because it can cause morning drowsiness. Too much magnesium (without the melatonin) also causes me significant drowsiness that can persist hours after awakening, so I know its doing something. Also when I was pregnant and having minor contractions too early in the pregnancy magnesium oxide worked quite well at controling the contractions, it was then I discovered its effect upon my sleep/insomnia.
I have always used "natures made" brand which is pretty cheap when it comes to name brands. Magnesium citrate seems to work the same for me but I cant find it in tablet form so that I can divide it in half if I need an extra dose during the night.