“Dr. Lee: Actually its both. By the way Finasteride (the active ingredient in Propecia) does work topically. When Merck was doing their trials, they had to make a decision as to what they felt would be a better selling product: A pill, or a topical applied solution. By far, people would rather take a pill, so this is the route they took. To answer your question: Why don’t topicals work as well? It’s for many reasons. One reason is that it doesn’t stay in the skin long enough. That’s the problem with progesterone. It’s absorbed, metabolized, and carried away so quickly that it’s not effective when it’s applied topically. Another problem is absorption. There are very few things that get absorbed into skin very well at all. Its quite the protective device.”
Excerpt from Merck’s patent description:
“[0031] The present invention has the objective of providing methods of treating the hyperandrogenic conditions of androgenic alopecia, including male pattern baldness and female pattern baldness, acne vulgaris, seborrhea, female hirsutism, and polycystic ovary syndrome by systemic, oral, parenteral or topical administration of a 5.alpha.-reductase 2 inhibitor in a dosage amount under 5 mg/day, and particularly, from about 0.01 mg/day to 3.0 mg/day, and more particularly 0.05 to 1 mg/day. The invention is further illustrated by dosages of about 0.05 to 0.2 mg/day and specifically dosages of about 0.05, 0.1, 0.15 and 0.2 mg/day. Exemplifying the invention are dosages of 0.05 and 0.2 mg/day. The term “treating androgenic alopecia” is intended to include the arresting and/or reversing of androgenic alopecia, and the promotion of hair growth. Also, a 5.alpha.-reductase 2 inhibitor, e.g. finasteride, at a dosage under 5 mgs/day can be used in combination with a potassium channel opener, such as minoxidil or a pharmaceutically acceptable salt thereof, for the treatment of androgenic alopecia, including male pattern baldness. The 5.alpha.-reductase 2 inhibitor and the potassium channel opener may both be applied topically, or each agent can be given via different administration routes; for example, the 5.alpha.-reductase 2 inhibitor may be a
