8 August 2003

Spanish group's experience with naltrexone implants.

Spanish group's experience with naltrexone implants. 'AddictionBiology' report.

Maintenance treatment with depot opioid antagonists in subcutaneousimplants: an alternative in the treatment of opioid dependence. Carren JE,Alvarez CE, San Narciso GI, Bascaran MT, Diaz M, Bobes J. Addiction Biology(2003) 8, 429-438

Dear Colleagues,

In this paper a group of Spanish naltrexone enthusiasts report on 156patients, nearly all male, who were treated with a rapid opioiddetoxification process followed by a naltrexone implant. It is due to the‘open’ policies of the editors of Addiction Biology that they are preparedto publish such papers. Research of this nature would be unlikely tosurvive the strict new ‘Farmington’ editorial rigours of the NAC ‘sister’journal, Addiction, edited by Griffith Edwards.

These researchers’ main finding is a two year follow-up with 4 six-monthlyretention rates of 80%, 65%, 55% and 21% “all of them remaining abstinent toopioids.” “It is concluded that the programme is safe for the patients andshows a better retention index than programmes using oral antagonists, withan improved compliance (negative urine analysis) compared to the latter.”Thus, although 80% of patients are lost to follow-up the authors seemconfident to report comparative results.

The authors also allow us to compare these naltrexone treated patients withthose prescribed methadone. Their reported statistics show only very minordifferences in social, drug use and other demographics over the 24 monthsfrom starting the treatment. This is in stark contrast to methadone andbuprenorphine patients who generally report dramatic and sustainedimprovements in employment, housing, drug use and criminal statistics afterjoining treatment. Indeed, despite finding a worrying increase in alcoholconsumption (mean 50%) over the period, the Spanish authors do not address this.It is also unfortunate that the authors of this naltrexone study do not givetheir specific clinical indications for the use of an experimental treatmentin preference to methadone or buprenorphine treatments which are the normal ‘gold standards’ for unstable opiate addiction in most western countries. At one point they give the feeble and almost embarrassing information thatnaltrexone is beneficial over methadone because it has no drug interactions,apart from the obvious one (the effects of opioids are negated in patients on naltrexone).

In our practice we have prescribed naltrexone to many patients over the years with a small number doing well for limited periods taking the oral formulation. Our indication for the use of naltrexone is for stronglymotivated patients seeking abstinence and who have faired poorly on agonist treatments. There is also a proportion of addicts who refuse to takemethadone and buprenorphine but their success rates on naltrexone do not seem to be any better than the others, the majority relapsing after stopping the medication, whether oral or implanted.
There may be sub-groups who do well with naltrexone but as long as research is done by ‘enthusiasts’ for the treatment in an undiscriminating manner, we will never learn what those subgroups are. Only randomised controlled research can resolve this question and the few such trials that there are to date using naltrexone are not encouraging for its use in non-selected opioid dependent patients.

Comments by Andrew Byrne ..