Let him go to another doctor for a second opinion. Sometimes (sadly, very often), it happens that the first doctor is just doing the wrong treatment.
I went to a gynaecologist once and she told me that "I will never have kids and we women always wait until the next minute and we do awful things to our bodies and then go to the doctor and want to give them money and expect miracles". These were her exact words and I left her office crying, after I agreed to come for some surgery. When I calmed down, I decided I want a sane doctor. I went to another one - TO A FREE CLINIC (we have plenty of these, actually, we pay a very small amount). The other doctor gave me some pills and told me that I went to a NUT CASE the first time. It really was a piece of cake.

I hope your brother gets well and I hope there is a treatment for his problem.