Would the use of cocaine once four months after a fue Hair Transplant have a big affect on the final result

If you are concerned about your cocaine use and your hair transplant, you need to follow up with your doctor.

At four months your transplants are essentially just as strong and resistant to damage as your normal hairs. Nothing you do at this point could really do significant damage to your them, barring severe trauma. But there are a variety of other reasons that I recommend against any sort of cocaine use.

At 4 months post hair transplant you are normal. You can do whatever you want and I doubt it will damage your transplants, and that includes cocaine. I am not recommending that you take cocaine, in case I just confused you.