longhair1983 said:
I would recommend try its 12.5% solution. I am a strong believer that higher concentration works better than lower one.
That's definitely true for versions of Rogaine with much
lower concentrations (like 2%, 1%, 0.5%, 0.25%, etc.), but there's no proof that it's also the case for versions of topical minoxidil that have much higher-than-normal concentrations (12.5%, 15%, etc.). There's never been a study which tested and compared the effects of such much-higher concentrations. It's all speculation from lay people, and may or may not be true.
longhair1983 said:
I don't think 2.5 ml 5% is not the same as 1 ml of 12.5%.
It might be, if you really spread the 2.5 mL out on your scalp enough, to maximize the total area of application. Again, though, that's more speculation; I don't think it's ever been tested by scientists.
I remind everybody again that the two standard versions of Rogaine (2% and 5%)
both turn into solutions of topical minoxidil in propylene glycol a little while after application which are maximized in concentration in that specific vehicle (about 7.5% or so).