Minoxidil on donor area from the beard? (Photo)

I have done my hair transplant 5 months ago. The doctor used my beard as a donor area and this part now has less density than the rest of the beard and it is not improving (shock-loss or over-harvested?). The representative of the clinic suggested me to use Minoxidil Rogaine 5 mg to get the hair back but I don't like what I read about its side-effects and the need to use it for a life-time! Do you think Minoxidil can be an effective solution to my problem? is it worth taking the risk in my case?