You are right to be worried, most people find it difficult to come of Suboxone. One of the patients in our clinic, who we had to detox from Suboxone, was so addicted, that no matter how far down she titrated this drug she could not get off. At one point she was literally just licking the 1 mg strip, but she could not give it up. I find that most have the same problem with this drug.
In case you are curious, it takes us about three to four days to get a patient off of any opiate including Suboxone, and feeling well. But what can you do to feel better now? See if a doctor can write your friend a prescription for some Requip for restlessness, Neurontin for anxiety and malaise, some Flexeril or Soma for a few weeks for muscle spasms and maybe some Seroquel low dose, for sleep and Klonopin which will be helpful for sleeplessness and anxiety. It will make his withdrawals easier. Valerian and Magnesium is sometimes helpful remedies over the counter.
The residual symptoms of insomnia and depression can last another few months. Thus, it is not easy, but it gets better and better over time and he can look forward to a drug free healthy energetic self in the future. When one takes opiates for a long time like you have, the body's physiology has been altered. The central nervous system has created a multitude of opioid receptors that all are screaming for endorphins (opiates) to fill them, but one's body has now forgotten how to make them by itself. It will take time - two to four weeks at least, for your receptors to down-regulate (for the brain begin to heal) and to start making its own endorphins. Brain heals pretty slowly, so it may take him as long as a couple of months to get rid of feelings of sluggishness, restlessness and depression. The best thing he can do is take good care of himself, eat healthy food, stay hydrated, keep active and busy. Stay away from sugar, soda, and simple carbs. Do not consume caffeine at least 6 hours prior to bedtime.
Take a look at my blogs about options for detox and recovery. You may also take a look at my clinic website where I also have my blogs and a lot of other info about drug addiction and recovery. Look especially into the blog and the info on Naltrexone therapy after getting clean. It really improves your chances of staying clean for good by cutting down your physical cravings. Look into my clinic website as well. All this can be done by clicking on my name in blue.