At least with women, studies indicate that the effects of topical flutamide are due to systemic absorbtion. BTW, the same is apparently true of topical finasteride.
So you might as well take it by mouth, although I cannot recommend that-- too many side-effects and it likely works little if any better than finasteride. Because of reflex hyperandrogenicity, it is necessary to castrate males taking this drug for prostate cancer to get longer-term effects.
My favorite antiandrogens are topical spironolactone or systemic finasteride. While on paper, spironolactone is much the stronger antiandrogen, as a practical matter it probably works little if any better on hair loss than systemic finasteride. Its chief advantage seems to lack of side-effects since spironlactone is not absorbed systemically from topical application.
Peter H. Proctor, PhD,MD