Q: I was wondering why you chose two years as the amount of time one should wait to judge the effectiveness of Propecia. Have you had patients who only saw results after that long? Why does Merck say 3-6 months and Dr. Rassman at New Hair say 6-8 months? I know these numbers aren’t arbitrary, but I’m just wondering what the logic is behind this and how does this relate to planning a hair transplant?

A: The Merck data showed that over 90% of patients had peak response at 1 year and this has been my experience as well.

Most patients show the most dramatic response between 6 to 12 months with some getting additional benefit up to two years. Prior to 6 months, the results are quite variable and there may even be a net loss due to shedding during this period, as the Propecia stimulates a new anagen cycle.

If one is planning to go on Propecia before a hair transplant to minimize any shedding from the surgery and to prevent future hair loss, one should start the medication at least one month prior to the procedure.

If one wants to use Propecia for the purpose of possibly avoiding hair restoration surgery, then one needs to wait at least a year to see if there will be enough regrowth.

Finally, if one is younger (i.e. in the 23-25 age range) one should be on Propecia for at least two years to give it every possible chance of working and see its maximum benefit before considering a hair transplant.