migraine
"20mg usually works great for me, as long as I do not wait too long to take it.  I weigh almost 90 lbs.  When more than several hours have passed since the start of the headache I take 40mg.   I ended up prefering Relpax (eletriptan) to sumatriptan.  Perhaps because it works better or perhaps because it is more convenient pill (no need to split).
I feel that it has a pain blocking effect for up to two days after taking it.  
My headaches originate from neck positions and movements and are about once a week."