Can I use minoxidil 5% right after hair transplant?

Tarek, 
You can continue using both minoxidil and finasteride after your transplant -- assuming your clinic agrees and you are side effect free. You will need to temporarily stop the minoxidil immediately after the transplant while the grafts are "anchoring." This time period varies between clinics. I tell my patients they can resume rubbing minoxidil on the scalp at 10 days post-op. The finasteride can be taken normally without any "stopping periods" before, during, or after the transplant. 
Dr. Blake Bloxham 
Great Neck, NY 

Rogaine or minoxidil can certainly be used after a hair transplant.  Particularly if you are new to minoxidil you may get some redness or flakiness of your scalp.  We advise our patients to wait until 10 days after a transplant to restart minoxidil.  This may avoid some of issues of scalp irritation.