Q: I know that Propecia works in only about half of patients. Are younger people more likely to be helped by this medication? — V.C. Greenpoint, Brooklyn

A: The main studies by Merck looked at men between the ages of 18 and 41. The five year data (which, in my view, is most important) showed that 48% of men had an increase in hair growth and 42% had no change over baseline. Thus a full 90% held on to their hair or had more over a 5-year period. This compares very favorably to the placebo group where 75% lost hair over the 5-year period.

I think the most interesting question relates to the 10% who continued to lose hair in the treated group. Did these men lose hair at a slower rate than the non-treated group? Based on the action of finasteride on blocking DHT and DHT’s central role in causing male pattern hair loss, it is reasonable to assume that even these “non-responders” did have some benefit from the drug, albeit small. If half of those on the medication who continued to lose hair did so at a rate slower than the placebo group, then 95% of patients actually benefited from the medication to some degree – an extraordinarily high success rate, in my opinion.