This insightful hair loss information was posted on our hair restoration forum by Dr. Jerry Cooley of Charlotte, NC who is a member of the Coalition of Independent Hair Restoration Physicians.
Propecia is approved by the US FDA for once a day use for hair loss. This does not mean it is the best dosage, only the one that was studied and approved. The average serum “half-life” of finasteride 1mg is about 5 hours in young men and 8 hours in older men. This does not mean that half of the medicine is out of your body in that time period though. The finasteride molecule is distributed throughout the body where it binds to the type II 5-alpha-reductase enzyme, thereby inhibiting conversion of testosterone to dihydrotesterone (DHT). Serum DHT is reduced about 65%, and less DHT means less balding. But several studies show that a single dose of finasteride suppresses serum DHT for 7 days or more (Eur J Drug Metab Pharmacokinet. 1991 Jan-Mar;16(1):15-21, J Clin Endocrinol Metab. 1990 Apr;70(4):1136-41, Prostate. 1989;14(1):45-53). So the finasteride is leaving the bloodstream, entering the tissue throughout the body, and binding to the type II 5AR (5-alpha-reductase) enzyme, resulting in long lasting DHT suppression.
I do not “recommend” my patients take finasteride daily, every other day, twice weekly, etc. Rather I feel it is my duty as their doctor to advise them of the known facts about this medication. Most of my hair loss patients choose to take it on a Mon-Wed-Fri schedule, which is rational from my point of view. Many of my younger patients take it daily ‘just to be sure’ while my older patients are happy to take it two or three times a week. There are no clinical studies showing that less than daily dosing is as effective to treat baldness as daily dosing and for obvious financial reasons, the pharmaceutical company making finasteride has no incentive to fund such a study.
I hope this information is helpful. It is up to each patient to make an informed decision about which dosage is right for them.
Dr. Jerry Cooley