Naltrexone is a drug used in the management of alcohol and opioid dependence. When taken, naltrexone attaches to the opiate receptors in the brain and blocks them, preventing the euphoric effect from the opiate. .
Naltrexone is available in oral, ‘depot’ (slow-release) injection or implant preparations, however only the oral and depot forms of naltrexone have been approved for use by the Food and Drug Administration (FDA). The potential benefits of a naltrexone implant include less frequent dosage and reduced rates of withdrawal and relapse between doses.
An assessment by the Australian National Health and Medical Research Council (NHMC, 2011) concluded that.naltrone implants are unproven for treatment of opioid dependence. The review concluded that evidence is currently at an early stage and as such, naltrexone implants remain an experimental product and should only be used within a research setting. Until the relevant data are available and validated, the efficacy of the treatment, alone or in comparison to best practice, cannot be determined (NHMC, 2011). NHMRC’s position on naltrexone implants is that further research on adverse effects is required before a statement on safety can be confidently made.
Specifically regarding the use of the naltrexone implant for alcoholism, a systematic evidence review concluded that larger longitudinal studies of the naltrexone implants are needed (Lobmaier, et al., 2011).
World Journal of Biological Psychiatry Guidelines on the Treatment of Substance Use and Related Disorders (2011) state: “Naltrexone implants cannot yet be recommended for clinical use because although there are promising efficacy data for them, safety concerns remain and require further evaluation.”
However, since then, some randomized controlled clinical trials of naltrexone implants have been published examining the effectiveness of the naltrexone implants for narcotic addictions. Limitations include the fact that these studies were not U.S. based, they examined short-term impact, and compared the implants to oral naltrexone rather than the depot injection (Vivitrol) that has been approved by the FDA.
Kelty and Hulse (2012) have reported on the mortality in cohorts of patients treated with oral and implant naltrexone. Some concerns with the methodology of this study have been raised including the comparison used; it was suggested that comparison with currently accepted modes of treatment such as opioid substitution treatment would be more appropriate (Hickman, et al., 2012).
There are some published reports of deaths attributable to naltrexone implants (Gibson, et al., 2007a; Gibson, et al, 2007b; Olivier, 2005) and other reports claiming significantly reduced mortality (Ngo, et al., 2008). Further research is needed to establish the risk of mortality during and after treatment with naltrexone implants and other treatment approaches.