could it be that your body got used to the new medication and that you could increase the dsage without further itching (or itching during 1-2 weeks?
I tried something like that that with finasteride. i was on one every other day for nearly 5 or 6 months and i thought maybe my body had got used to taking finasteride by then and i could maybe go on it daily with no more itch... so i went back to every day and the itch ended up caming back... admittedly it wasn't as bad as when i first started taking the first time every day it but it was still more or less a 3 to 5 second strong tingle around the hairline that came and went through out the day.
I am told taking it every other day shouldn't be that much different but for some reason it clearly is.