I'm guessing he is probably on something called Antabuse/Naltrexone..

The problem with drugs like this, or even pain meds themselves, is it ALSO blocks natural Endorphins. Think of it like this - the body produces endorphins right - well endorphine is actually short for "Endomorphine".. it is the bodies natural opiate. Endorphines are part of what gives us that "rush" when happy, or when we are excersizing, or in pain. And yes, its also part of what gives us the Sexual "rush" or lust. So it makes complete sense that he is experiencing this.

Let me talk to some of my friends who are on it. I will get back to you and see if there is something that can be done.