Would the use of cocaine post op effect the the FUE hair transplant?

The use of cocaine can absolutely affect an FUE hair transplant.  We know cocaine is a potent vasoconstrictor of blood vessels.  We also know that when grafts are transplanted, they need as much blood supply as they can get.  Using cocaine can theoretically limit this.  If you need to use cocaine after your hair transplant, it would be more wise to address your cocaine use, quit, and then worry about the hairless.

Are you looking for reassurance so that you can use cocaine recreationally?  Or, have you used cocaine after your surgery and now trying to assuage your guilt because you believe it ruined the outcome of your surgery?You can try to find the answer here that best suits your needs but the take home message was best said by Mr. Mackey

Cocaine can limit the blood flow to new grafts (like smoking can do) so I would recommend you not use it after your surgery, both to ensure your transplant has the best results but also for a variety of other reasons. Is it really worth the risk?

Highly advise against cocaine for many health reasons besides the results of a FUE hair transplant.  Cocaine also reduces blood flow thus decreasing graft survival. - Dr. Keaney

The blood supply of the scalp is very rich and even a vaso-constrictor such as Cocaine or Smoking may have minimal effect. In any event, to pay it safe, stay away from heavy cocaine use after having a hair transplant for any potential compromise on blood supply. I know of no scientific study that either conforms or denies any impact of cocaine on hair transplants but because there is no evidence one way of the other, that should not be a reason to take the theoretical gamble