Q: I heard that the sexual side effects of Propecia are irreversible. Is this true? — L.R., Parsippany, NJ

A: The sexual side effects of finasteride (Propecia) begin to subside soon after the medication is discontinued. This would make sense since the drug finasteride is a reversible inhibitor of DHT. Although it is possible for side effects to be persistent after stopping the medication, this situation seems to be very uncommon and a cause and effect relationship is still in question.