Both generic and brand name have the same active ingredient.
Minoxidil (generic)is equivalent to Rogaine(brand)so u can take either one. Generic is lot cheaper.
Here is my understandig--If minoxidil is not equivalent to the brand name then FDA would have never approved it.
According to FDA- The generic manufacturer must have to show that the generic drug is "bioequivalent" to the brand-name drug, while brand name manufacturer have actually done the "bioequivalent" studies (clinical trials- very expensive studies).
There are so many other FDA requirements such as labeling,strength,stability,gamp,formulation.