E.B.
I get this every time I take it for more then three days.
Then it lasts until I dont take it any more.
I get it with all the mega strong pain meds. Vicodin, morphine...anything higher then morphine gives me a migraine.
Drink lots of water while you are taking them. I think that is what causes some of the headache...the meds dry you out like a sponge on a counter.