Naltrexone Implants

Number: 0878

Policy

Aetna considers naltrexone implants experimental and investigational for the treatment of the following (not an all-inclusive list) because of insufficient evidence in the peer-reviewed published medical literature of their safety and effectiveness.

• Alcohol addiction
• Amphetamine use
• Autism spectrum disorders
• Buprenorphine dependence
• Impulse control disorders in Parkinson disease
• Narcotic addiction
• Prolactinoma (prolactin-secreting pituitary tumor)
• Trichotillomania

Note: This CPB does not apply to Vivitrol Injections (J2315).

Background

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.

Kelly et al (2013) examined self-reported abstinence from amphetamines following treatment with a sustained release naltrexone preparation in patients with self and clinically identified problems with amphetamine use and the relationship between naltrexone blood levels and abstinence from amphetamines.  A total of 44 patients with problematic amphetamine use, who were treated with a naltrexone implant, completed an interview evaluating self-reported reduction in amphetamine use following treatment.  Additional data were collected from the patients' clinical treatment files.  Of the 44 subjects, 29 (65.9 %) interviewed reported that following treatment they ceased using and maintained abstinence from amphetamines for at least 1 month.  Of these patients, 14 (48.3 %) were reportedly still abstinent at 6 months.  Rates of abstinence were found to be 2.27 times higher (95 % % confidence interval (CI): 1.38 to 3.74) in patients when blood naltrexone levels were above 2 ng/ml, with rates as high as 100 % and 90.9 % for greater than or equal to 5 and greater than or equal to 2 ng/ml, respectively, compared with 42.9 % for 1 to 2 ng/ml and 38.9 % low less than 1 ng/ml.  The authors concluded that although this study has several limitations, the findings provided preliminary data in support of the use of implant naltrexone for the treatment of problematic amphetamine use and suggested that naltrexone levels above 2 ng/ml should be targeted for use in patients.  Moreover, they stated that further research is needed.

Larney et al (2014) systematically reviewed the literature to evaluate the safety and effectiveness of naltrexone implants for treating opioid dependence.  Studies were eligible if they compared naltrexone implants with another intervention or placebo.  Examined outcomes were induction to treatment, retention in treatment, opioid and non-opioid use, adverse events, non-fatal overdose and mortality.  Quality of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation approach.  Data from randomized studies were combined using meta-analysis.  Data from non-randomized studies were presented narratively.  A total of 5 randomized trials (n = 576) and 4 non-randomized studies (n = 8,358) were eligible for review.  The quality of the evidence ranged from moderate to very low.  Naltrexone implants were superior to placebo implants [risk ratio (RR): 0.57; 95 % confidence interval (CI): 0.48 to 0.68; k = 2] and oral naltrexone (RR: 0.57; 95 % CI: 0.47 to 0.70; k = 2) in suppressing opioid use.  No difference in opioid use was observed between naltrexone implants and methadone maintenance (standardized mean difference: -0.33; 95 % CI: -0.93 to 0.26; k = 1); however, this finding was based on low-quality evidence from 1 study.  The authors stated that the evidence on safety and effectiveness of naltrexone implants is limited in quantity and quality, and the evidence has little clinical utility in settings where effective treatments for opioid dependence are used.  They concluded that better designed research is needed to establish the safety and effectiveness of naltrexone implants; until such time, their use should be limited to clinical trials.

Autism Spectrum Disorders:

Roy and colleagues (2015) stated that autism spectrum conditions (ASC) may result from a failure of striatal beta endorphins to diminish with maturation. Many symptoms of ASC resemble behaviors induced in animals or humans by opiate administration, including decreased socialization, diminished crying, repetitive stereotypies, insensitivity to pain and motor hyperactivity.  Naltrexone, an opioid antagonist, has been used in the management of children with ASC and can produce a clinically significant reduction in the serious and life-threatening behavior of self-injury for individuals who have not been responsive to any other type of treatment and is important for this reason.  In a systematic review, these researchers reviewed the available evidence regarding the use of opioid antagonists in attenuating the core symptoms of ASC in children.  Four electronic databases were searched for relevant journal articles.  In addition, cross-referencing of pertinent reviews and a hand-search for articles in major international intellectual disability (ID) journals between the years 2010 and 2012 was carried out to ensure that all relevant articles were identified.  These investigators also searched databases for unpublished clinical trials to overcome publication bias.  Each database was searched up to present (February 2013) with no restrictions on the date of publication.  The search terms consisted of broad expressions used to describe ID and autistic spectrum disorder (ASD) as well as terms relating to opioid antagonists and specific drugs.  All studies identified by the electronic database search and hand-search were examined on the basis of title alone for relevance and duplication.  The abstracts of the remaining papers were then scrutinized against the inclusion criteria.  Where abstracts failed to provide adequate information, the full texts for these papers were obtained.  All the full texts were then evaluated against the inclusion proforma.  Two reviewers carried out all the stages of the process independently.  The reviewers met to discuss their selections and where disagreements arose, these were settled by discussion with a member of the study group.  Data from each study meeting the inclusion criteria were extracted on a pre-piloted data extraction form.  The quality of each study was further assessed using the Jadad scale, a tool developed to assess the quality of randomised controlled trials.  A total of 155 children participated in 10 studies; 27 received placebo.  Of the 128 that received naltrexone, 98 (77 %) showed statistically significant improvement in symptoms of irritability and hyperactivity.  Side effects were mild and the drug was generally well-tolerated.  The authors concluded that naltrexone may improve hyperactivity and restlessness in children with autism but there was insufficient evidence that it had an impact on core features of autism in majority of the participants.  They stated that it is likely that a subgroup of children with autism and abnormal endorphin levels may respond to naltrexone and identifying the characteristics of these children must become a priority.

Impulse Control Disorders in Parkinson Disease:

In a placebo-controlled study, Papay et al (2014) determined the tolerability and effectiveness of naltrexone for the treatment of impulse control disorders (ICDs) in Parkinson’s disease (PD). Patients with PD (n = 50) and an ICD were enrolled in an 8-week, randomized (1:1), double-blind, placebo-controlled study of naltrexone 50 to 100 mg/day (flexible dosing).  The primary outcome measure was response based on the Clinical Global Impression-Change score, and the secondary outcome measure was change in symptom severity using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale (QUIP-RS) ICD score.  A total of 45 patients (90 %) completed the study.  The Clinical Global Impression-Change response rate difference favoring naltrexone in completers was 19.8 % (95 % CI: -8.7 % to 44.2 %).  While this difference was not significant (odds ratio [OR] = 1.6, 95 % CI: 0.5 to 5.2, Wald χ2 [df] = 0.5 [1], p = 0.5), naltrexone treatment led to a significantly greater decrease in QUIP-RS ICD score over time compared with placebo (regression coefficient for interaction term in linear mixed-effects model = -7.37, F[df] = 4.3 [1, 49], p = 0.04).  The estimated changes in QUIP-RS ICD scores from baseline to week 8 were 14.9 points (95 % CI: 9.9 to 19.9) for naltrexone and 7.5 points (95 % CI: 2.5 to 12.6) for placebo.  The authors concluded that naltrexone treatment was not effective for the treatment of ICDs in PD using a global assessment of response, but findings using a PD-specific ICD rating scale support further evaluation of opioid antagonists for the treatment of ICD symptoms in PD.

Trichotillomania:

In a double-blind, placebo-controlled study, Grant et al (2014) examined the effectiveness of naltrexone in adults with trichotillomania (TTM) who had urges to pull their hair.  A total of 51 individuals with TTM were randomized to naltrexone or placebo in an 8-week, double-blind trial.  Subjects were assessed with measures of TTM severity and selected cognitive tasks.  Naltrexone failed to demonstrate significantly greater reductions in hair pulling compared to placebo.  Cognitive flexibility, however, significantly improved with naltrexone (p = 0.026).  Subjects taking naltrexone with a family history of addiction showed a greater numerical reduction in the urges to pull, although it was not statistically significant.  The authors concluded that future studies are needed to examine if pharmacological modulation of the opiate system may provide promise in controlling pulling behavior in a subgroup of individuals with TTM.

Buprenorphine Dependence:

Jhugroo and associates (2014) stated that although substitution therapy with opiate agonist treatments such as methadone and buprenorphine has resulted in a reduction of illicit drug use related harm, such treatment has also resulted in severe problems in some countries where opioid-dependent individuals now inject illicitly sold buprenorphine or buprenorphine-naloxone instead of heroin.  There is no approved treatment for buprenorphine dependence.  Naltrexone is an opioid antagonist that has been used for the treatment of both alcohol and opioid dependencies.  Although both buprenorphine and heroin resemble each other concerning their effects, buprenorphine has a higher affinity to opioid receptors than heroin.  Thus, it is unclear if naltrexone can block the psychoactive effects of buprenorphine as it does for heroin.  The authors presented observational case-series data on the use of a sustained-release naltrexone implant for the treatment of buprenorphine dependence.  To the authors' knowledge, this was the 1st use of sustained-release naltrexone for this indication.  The use of naltrexone implants for the treatment of buprenorphine dependence needs to be further investigated.

Prolactinoma (Prolactin-Secreting Pituitary Tumor):

Maglakelidze and colleagues (2017) stated that prolactinoma (prolactin-secreting pituitary adenomas) is the most common pituitary tumors in humans.  Animal studies have identified aggressive prolactinoma development in fetal alcohol exposed rats.  These researchers have recently identified a combination treatment of a μ opioid receptor antagonist naltrexone and a δ opioid receptor agonist D-Ala2-,N-Me-Phe4,Gly-ol Enkephalin (DPDPE) increases innate immune function.  In this study, these investigators  examined if naltrexone and DPDPE combination therapy is useful to control pituitary tumor growth.  Fetal alcohol exposed and control Fischer 344 female rats at 60 days of age were ovariectomized and received an estrogen implant to induce prolactinomas.  Six weeks after the estrogen implant, these animals received treatments of naltrexone and DPDPE or saline.  The growth of the pituitary tumor prior to and after opioidergic agent treatments was visualized using magnetic resonance imaging (MRI).  At the end of the treatment, pituitary weights, plasma prolactin and splenic levels of cytotoxic factors were determined.  Both imaging data and weight data indicated that the volume and the weight of the pituitary were increased more after estrogen treatment in animals exposed to fetal alcohol than control.  Naltrexone and DPDPE treatment reduced the weight and volume of the pituitary gland and plasma levels of prolactin in both fetal alcohol exposed and control-fed animals.  The treatment of opioidergic agents also increased the levels of cytotoxic factors in the spleen.  The authors concluded that these data provided a novel possibility in treating pituitary tumors using a combination therapy of naltrexone and DPDPE.

The above policy is based on the following references: