i had a lot of problems with this myself. at first i got some dandruff from minoxodil, but that was no big. over this past summer it suddenly developed into a serious problem- major flaking, dandruff all over, itching a lot, and i was losing more hair than i ever was before.
i had always used head & shoulders to combat the mild dandruff before. when this problem started i added in nizoral every 3 days; it helped get the major inflammation under control but i too found that it dried out my hair and scalp and still left me with too much dandruff, even after 2 months of treatment.
i read on webmd that all of the major dandruff shampoos have different active ingredients, and everyone reacts differently. so i tried the generic cvs equivalent of selsun blue. my dandruff and inflammation was totally cleared up almost immedietly.
so my current regimen is selsun blue everyday, nizoral every 3rd of 4th day (and i wash the nizoral out with regular shampoo afterwards), and a vitmain C supplement every morning. it totally stopped my dandruff and i've noticed a huge reduction in the amount of hair coming out, in the shower at least.