I take it twice a day and I do get headaches when I dont take it every 12 hours, I can always tell when I havent had my meds on time. It is a bizarre thing because my pdoc was surprised too. Now I take a small dose in the morning and a larger dose at night but many people have no problem with taking it all at once. I think I was started on it twice a day so that I would be properly medicated over the 24 hours with no wear off effects.

The side effects for the first few days do wear off after about 2 weeks. I had a whole lot of side effects at first but they wore off really quickly and the med started to really work in 10 days.