Recent developments in naltrexone implants and depot injections for opiate abuse: the new kid on the block is...

Implants and depot injections (DI) of naltrexone (NTX) have undergone considerable development since the first commercially available implants appeared in the mid-1990s. In particular, long-acting implants that can deliver relapse-preventing serum NTX levels for around six months have now been subjected to classic randomised controlled trials that have given positive and generally significant results when compared with oral NTX and placebo implants, or with standard post-detoxification care. They also provide lower serum levels that can prevent opiate overdose for several additional months and 3-year mortality rates are similar to those of methadone maintenance treatment (MMT). At least 18 months of antagonist-assisted abstinence may be desirable to normalise new, opiatefree cognitive-behavioural habits and extinguish old, maladaptive ones. We discuss ideological antagonisms between protagonists of MMT and of NTX implants, notably in Australia, but we argue that both treatments can and should co-exist. The main obstacle to the expansion of longacting implant treatment is not the lack of an evidential or theoretical base but the lack of a licensed product. NTX appears to block all opiates if serum levels are adequate and we stress its apparent lack of clinically significant hepatotoxicity. Some patients may need above-average serum levels and occasionally, habitual injectors continue to inject opiates despite experiencing no opiate effects.