"Early dose ranging studies showed that much smaller dosages, such as 0.5 mg and even less, inhibited DHT on average almost as well as much higher dosages, such as 5 mg. One 6-month study comparing a placebo group, which lost hair, to users taking differing dosages of finasteride found that 0.2 mg of finasteride increased hair counts about 81% as much as 1 mg when compared to the placebo.
Similarly, 1 mg increased hair counts 82% as much as a full 5 mg compared to placebo. The tiny 0.2 mg dosage did about 66% as well at regrowth and retention as 5 mg. Accordingly, the 1 mg dosage was probably a compromise designed to be high enough to pick up those who may not respond as well to the lower dosages, but low enough to minimize side effects.
Many of those who take less than 1 mg opt for either 0.5 mg or 0.625 mg (1/8th of a Proscar tablet). Some people also skip days periodically based on the fact that finasteride suppresses DHT for up to several days and also on the old pharmacological rationale that it may help preclude any possible tendencies toward tolerance, which sometimes happens with continuous long-term use of medications"
