My dermatologist gave me meds for a couple of months and suggested 6 sessions of PRP afterward (1 per month). He had mentioned that PRP effects take at least 3 months to show and a couple family members did notice some difference. I sense that the treatment has slowed hair loss a bit but it is difficult to gauge how much. I'll have to do PRP sessions once every few months along with regular application of a scalp spray and special shampoo.
From what I have read and what my dermatologist told me, PRP (or any other treatment for male pattern baldness) doesn't work for everyone. You have to experiment and see what works for you.
Hair transplant is the only long-term solution. How long it will last depends on donor area's hair quality.