Its alright for spot treatment, but keep in mind that's all it's good for.
Surrounding areas will still be affected by DHT, and the only possible way to counter act this is to inhibit it orally through the blood.
What most people don't understand is that all though some may receed in a pattern fashion, every where else is gradually being diffused in addition to the areas that are most noticible.
it's not uncommon for someone to become NW3 then all of a suddent start diffusing through out their whole scalp.