And Asecin, you could try memantine. It is one hell of an effective assist for opioid detoxing. At high doses (50-100mg BD, or even TDS if you take to it, especially with a little alpha2 agonist, such as clonidine, a few hundred mikes a few times a day, or the shorter acting tizanidine (less hypotensive, shorter acting than clonidine, but far more myorelaxant) can work wonders.
I got nicked once, and the fucking filthy bastard pigs tried to use opioid withdrawal as a method of coercion to get information out of me and a false confession. But that particular time, I'd taken a couple of hundred mg of memantine the previous day, along with my opioid dose. I'd had no opiates (being on 110-120mg morphine IM BD min. and 80mg oxy daily minimum (the oxy used to be lower, but was increased after I burnt my eye, courtesy of the filth interfering with the labels on certain bottles containing things that need not be mentioned specifically but were all of them alkaline, some damn strong bases and none of them anything you want close to your eyes, that resulted in a pressurized, ammonia propelled jet of boiling hot basic, salts-laden slops that punched through a bottlecap and hit at an upward angle hard enough to knock the protective goggles up off my eyes and allow the rest of that stream of searing hot, highly basic corrosive shite to belt me one right in the eye, resulting in an emergency hospital trip, a fuckton of absolute screaming agony the likes of which I barely thought possible to exist, and that makes a white phosphorus burn on a kid, look and feel like paradise, along with a HClO4 burn (relatively mild considering what could have happened) plus a SOCl2-induced degloving of 3/4 of one hand, down to the bare raw, acid-soaked smoking muscle, whilst having your testicles slowly burst in a red-hot vice coated in fuming sulfuric acid (albeit I've never had the experience of the bit with the testicles, but the rest of it put together wasn't anywhere near that nasty and painful)
So at the time, I'd developed an even larger tolerance to opiates, and was sometimes using street H or H/fent or fent derivative type strong-ass but short duration opioid mixture, and the memantine plus clonidine even helped take away some of the horrendous pain (was still wearing an eyepatch at that point, it should be noted, because exposure to light was still causing me great pain), and the filth tried to use that, and forced withdrawal (I HAD my meds with me, taken to the station, and they were holding them over me, threatening to force me to wait for many hours until I ever got to see a doctor), and I managed to hold out, giving them an entirely 'no comment' statement, aside from the mandatory name, address and D.O.B.
I am pretty sure I'd have cracked, eventually, if it hadn't been for having that hefty dose last taken of memantine in me, and its long duration of effect. I even SLEPT in the holding cell. (not before urinating all over the meat-wagon mind you, walking around it slowly with my knob out and making sure to take extra time to piss under and on the door-handles of the driver-side and front left side door, whilst making sure they kept their distance until I'd finished, telling them if they came in range, the target would switch from cop van to porkers themselves
)
(yes, the pricks have it in for me, have done for a long time, and I was dying for a piss by the time I'd been taken to a pig shop a long, long way from the one that is minutes driving from where I was), so I'd really had it with the fuckers, and decided it was time for some payback to begin, although I've launched legal action too, aside from getting the personal satisfaction of pissing all over a cop car and making sure extra attention was given to the door handles of the twunts)