Not to be a pessimist, but detoxing from that would be a nightmare. Then again it also depends how long he has been on the meds. If he built that tolerance up in the space of about a year, it might not be so bad. My advice would be to arm yourself with a massive arsenal of knowledge of various classes of sedatives and different drugs which can remedy withdrawal symptoms (but remember never to take any one class of drug for too long because you don't want to add a new dependence), as well as supplements, drugs and activities to accelerate your recovery. I have done plenty of research on drug withdrawals and ways to recover from them in less painful ways, so I can help you out if you do decide to get drug free in the future, just send me a PM.
BTW I agree with medicine cabinet that a slow taper is the way to go. Rapid detoxes can cause problems like brain damage (due to glutamate excitotoxicity and other factors). Also, make sure to take loads of antioxidants, magnesium, low dose NMDA antagonists, multivitamins and other beneficial things during the taper, that will protect your brain and accelerate the recovery process.
EDIT: I also recommend bringing spirituality into your life, if you haven't already. Ayahuasca is a great tool for recovery. I watched some of my PAWs vanish after a single ceremony. It helps you deal with your deep seeded psychological problems, and helps wipe out psychological addictions.