Tweetfinasteride blocks the conversion of test to DHT, so you have less DHT floating around to attack your hair or prostate. spiro is a topical anti-andrognen that attacks the DHT at the scalp, which is a more feasible choice of the two. but both are best used together. less DHT converted with finasteride, and no DHT allowed to attach to your scalp with spiro. nizoral is just all around good stuff for your scalp and hair as well as acne.