Withdrawals from opiates are actually caused by the activation of TLR family by a metabolite of the opiate. So for example heroin metabolises into M3G and M6G.
M6G binds to the mu receptors and M3G binds to the TLR4 receptor which floods your body with proinflammatory cytokines. These things create resetless leg, nasua, aches and pains - basically withdrawals. But when you think about it its not the absence of the heroin that is causing it but rather the absence of the M6G which was covering up the pain and agony of the proinflammatory cytokines caused by M3G.
THink if heroin didn't have any M6G but only M3G it wouldn't be a nice drug. It would make you feel like you're in instant withdrawals whenever you shoot it up.
Incidentally improper activation of TLR4 is thought to cause MS. So basically heroin withdrawal syndrome is actually the same thing a MS patient is going through (but never stops) but without any of the analgesic affects of the heroin.
So anyway. back to Polo792. It won't matter if you're on Naltrexone, heroin or whatever. Anything that activates the Toll Like Receptor family, like the metabolite M3G, or B3G (bbuprenorphine-3-glucuronide) is gonna mean that once the pain reliving effect is gone that your gonna feel dope sick.
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1.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2783351/ for more reading.
2.
http://www.huffingtonpost.com.au/entry/meth-addiction-cure-ucla-ibudilast_n_2863126