How long after the hair implant, I can start using Minoxidil 5%?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.   Minoxidil is not necessary for transplanted hairs to grow.

After
a hair transplant we ask that patients wait 7 days before starting minoxidil.
However, if by some chance you still have open wounds and excessive scabbing,
hold off for a few more days until after the wounds have closed.

I usually tell my patients to wait a week before resuming minoxidil, though as you can see from the other answers different surgeons have different opinions.  You should check with your surgeon for his/her preference.

Minoxidil is a nice companion to a hair transplant. The goal is to keep as much hair as possible and put off future transplants. Minoxidil can normally be resumed within about two wweks after the transplant.William P. Coleman III, MDEditor In Chief, Dermatologic SurgeryClinical Professor of Dermatology, andAdjunct Professor of Surgery (Plastic Surgery)Tulane University Health Sciences CenterNew Orleans, Louisiana504-455-3180

If you were not on Minoxidil before the transplant, don't use it. IF you are picking it up again, then 10 days later will be fine and safe