A possible role for implantable naltrexone in the management of the high-risk pregnant heroin user

Use of naltrexone in treating opioid use disorder in pregnancy

BACKGROUND

The mainstay of the management of opioid use disorder in pregnancy is with methadone or buprenorphine medication-assisted treatment. Methadone and buprenorphine are opioid agonist drugs. Naltrexone, an opioid antagonist, is also a medication-assisted treatment option; however, to date, only a few retrospective studies have reported its use in pregnancy.

OBJECTIVE

Our study objective was to evaluate prospectively obstetric and newborn outcomes and the maternal/fetal effects of the use of naltrexone as a medication-assisted treatment in pregnant patients with opioid use disorder.

STUDY DESIGN

We performed a prospective cohort study collecting data on all pregnant women who were treated with naltrexone medication-assisted treatment compared with pregnant women who were treated with methadone or buprenorphine medication-assisted treatment. Based on a sample size calculation, it was determined that for a power of 90, a minimum of 160 study participants (80 in each group) was needed with an alpha of .01 and an expected 60% rate of newborn infants who were treated for neonatal abstinence syndrome in the methadone or buprenorphine medication-assisted treatment group compared with a 30% rate in the naltrexone medication-assisted treatment group. In a random subset of 20 maternal/newborn dyads, blood levels for naltrexone and 6-beta-naltrexol (an active metabolite) were analyzed at delivery.

RESULTS

A total of 230 patients were studied: 121 patients with naltrexone medication-assisted treatment compared with 109 patients with methadone or buprenorphine medication-assisted treatment. No differences between groups were seen regarding demographics, the use of comedications/drugs, or obstetric outcomes. For newborn outcomes, the rate of neonatal abstinence syndrome in neonates >34 weeks gestation was significantly lower in the naltrexone medication-assisted treatment group (10/119 [8.4%] vs 79/105 [75.2%]; P<.0001). Multivariate analysis demonstrated that the only significant factor for the rate of neonatal abstinence syndrome was the form of medication-assisted treatment. Of 87 patients who received naltrexone up to delivery, no neonates experienced symptoms of neonatal abstinence syndrome. No maternal relapses occurred in the 7-day no-treatment window before the initiation of naltrexone therapy. No cases of spontaneous abortion or stillbirth occurred in either group. In 64 patients who started naltrexone therapy at ≥24 weeks gestation, no changes were seen in the fetal heart monitor tracing with drug initiation. The incidence of birth anomalies was no different between the groups. Umbilical cord blood and maternal levels for naltrexone and 6-beta-naltrexol matched; no levels were elevated, and values were undetected if naltrexone was discontinued >60 hours before delivery.

CONCLUSION

These study data demonstrate that, in pregnant women who choose to completely detoxify off opioid drugs during gestation, naltrexone, as a continued form of medication-assisted treatment, is a viable option for some pregnant patients who experience opioid use disorder. Naltrexone crosses the placenta, and maternal and fetal levels are concordant. Because naltrexone clears quickly from the maternal circulation, this rapid clearance needs to be addressed with patients. This is important because maternal relapse could occur in a short time-period if the oral drug is discontinued without the knowledge of their healthcare providers. Nonetheless, the drug is well-tolerated by both mother and fetus, and newborn infants do not experience symptoms of neonatal abstinence syndrome if naltrexone medication-assisted treatment is maintained to delivery.

A Retrospective Cohort Study of Birth Outcomes in Neonates Exposed to Naltrexone in Utero: A Comparison with Methadone-, Buprenorphine- and Non-opioid-Exposed Neonates

BACKGROUND

Naltrexone may provide a suitable alternative to methadone and buprenorphine in the treatment of pregnant opioid-dependent women; however, little is known about its effects on neonatal morbidity and mortality.

OBJECTIVE

The aim was to evaluate the health of neonates exposed to naltrexone in utero, and compare it with outcomes in neonates exposed to methadone or buprenorphine and a non-exposed control group.

METHODS

Sequential cohorts of Western Australian (WA) opioid-dependent women treated with implant naltrexone, oral methadone or sublingual buprenorphine were identified via records from a drug and alcohol clinic (Subiaco, WA) for naltrexone and state prescribing records for methadone and buprenorphine. A control cohort of non-opioid-dependent women was obtained from the WA electoral roll. Identifying information and treatment records for these women were linked against the Midwife Notification System records to identify exposed offspring born between 2001 and 2011. Birth characteristics, congenital anomalies and perinatal mortality for all neonates were extracted from state records.

RESULTS

The birth characteristics of naltrexone-exposed neonates (n = 68) were superior to methadone-exposed neonates (n = 199) in terms of birth size (birth weight, head circumference and length), hospital length of stay (5.5 vs. 11.3 days), and rates of neonatal abstinence syndrome (NAS) (7.5 vs. 51.5%). Naltrexone-exposed neonates were generally not significantly different to buprenorphine-exposed neonates (n = 124), with the exception of significantly lower rates of NAS (7.5 vs. 41.8%) and shorter hospital length of stay (5.5 vs. 8.0 days) in naltrexone-exposed neonates. Compared with the control group of neonates (n = 569), naltrexone-exposed neonates were not significantly different in terms of overall rates of congenital anomalies, stillbirths and neonatal mortality; however, they were significantly smaller (3137.1 vs. 3378.0 g), spent more time in hospital following birth (5.5 vs. 4.3 days) and had higher rates of NAS (7.5 vs. 0.2%). Exposure of neonates to prenatal methadone was associated with a high incidence of neonatal mortality (2.0 vs. 0.2 per 100 live births) and congenital anomalies (10.6 vs. 4.4 per 100 births) compared with the control group. Rates of neonatal mortality and congenital abnormalities in buprenorphine-exposed neonates were not significantly different to the control group.

CONCLUSIONS

The use of implant naltrexone during pregnancy was not associated with higher rates of negative birth outcomes compared with methadone- and buprenorphine-exposed neonates. Significantly, naltrexone and buprenorphine were not associated with the high rates of neonatal mortality or congenital anomalies seen in methadone-exposed neonates.

Caring for Pregnant Women with Opioid Use Disorder in the USA: Expanding and Improving Treatment

PURPOSE OF THE REVIEW

Opioid use disorder in the USA is rising at an alarming rate, particularly among women of childbearing age. Pregnant women with opioid use disorder face numerous barriers to care, including limited access to treatment, stigma, and fear of legal consequences. This review of opioid use disorder in pregnancy is designed to assist health care providers caring for pregnant and postpartum women with the goal of expanding evidence-based treatment practices for this vulnerable population.

RECENT FINDINGS

We review current literature on opioid use disorder among US women, existing legislation surrounding substance use in pregnancy, and available treatment options for pregnant women with opioid use disorder. Opioid agonist treatment (OAT) remains the standard of care for treating opioid use disorder in pregnancy. Medically assisted opioid withdrawal ("detoxification") is not recommended in pregnancy and is associated with high maternal relapse rates. Extended release naltrexone may confer benefit for carefully selected patients. Histories of trauma and mental health disorders are prevalent in this population; and best practice recommendations incorporate gender-specific, trauma-informed, mental health services. Breastfeeding with OAT is safe and beneficial for the mother-infant dyad.

SUMMARY

Further research investigating options of OAT and the efficacy of opioid antagonists in pregnancy is needed. The US health care system can adapt to provide quality care for these mother-infant dyads by expanding comprehensive treatment services and improving access to care.

Injectable and implantable sustained release naltrexone in the treatment of opioid addiction

Sustained release technologies for administering the opioid antagonist naltrexone (SRX) have the potential to assist opioid-addicted patients in their efforts to maintain abstinence from heroin and other opioid agonists. Recently, reliable SRX formulations in intramuscular or implantable polymers that release naltrexone for 1-7 months have become available for clinical use and research. This qualitative review of the literature provides an overview of the technologies currently available for SRX and their effectiveness in reducing opioid use and other relevant outcomes. The majority of studies indicate that SRX is effective in reducing heroin use, and the most frequently studied SRX formulations have acceptable adverse events profiles. Registry data indicate a protective effect of SRX on mortality and morbidity. In some studies, SRX also seems to affect other outcomes, such as concomitant substance use, vocational training attendance, needle use, and risk behaviour for blood-borne diseases such as hepatitis or human immunodeficiency virus. There is a general need for more controlled studies, in particular to compare SRX with agonist maintenance treatment, to study combinations of SRX with behavioural interventions, and to study at-risk groups such as prison inmates or opioid-addicted pregnant patients. The literature suggests that sustained release naltrexone is a feasible, safe and effective option for assisting abstinence efforts in opioid addiction.

Naltrexone in the treatment of opioid-dependent pregnant women: the case for a considered and measured approach to research

The present paper considers naltrexone to treat opioid dependence during pregnancy. The public health problem of opioid dependence and its treatment during pregnancy is reviewed first. Next, the naltrexone and opioid dependence treatment literature is summarized, with overviews of the pre-clinical and clinical research on prenatal naltrexone exposure. Finally, considerations and recommendations for future medication research for the treatment of opioid dependence in pregnant women are provided. The efficacy of long-acting injectable naltrexone relative to placebo, its blockade of opioid agonist euphoric effects, its lack of abuse and tolerance development and its modest adverse effect profile make it a potential medication for opioid-dependent pregnant women. However, it is not without seriously concerning potential drawbacks, including the difficulty surrounding medication induction that may lead to vulnerability with regard to relapse, physical dependence re-establishment, increased risk behaviors, treatment dropout and resulting opioid overdose. Before embarking on future research with this medication, the benefits and risks for the mother-embryo/fetus/child dyad should be weighed carefully. Should future research be conducted, a multi-level commitment to proactive ethical research is needed to reach the ultimate goal of improving the lives of women and children affected by opioid dependence.

Maternally administered sustained-release naltrexone in rats affects offspring neurochemistry and behaviour in adulthood

Naltrexone is not recommended during pregnancy. However, sustained-release naltrexone implant use in humans has resulted in cases of inadvertent foetal exposure. Here, we used clinically relevant dosing to examine the effects of maternally administered sustained-release naltrexone on the rat brain by examining offspring at birth and in adulthood. Maternal treatment (naltrexone or placebo implant) started before conception and ceased during gestation, birth or weaning. Morphometry was assessed in offspring at birth and adulthood. Adult offspring were evaluated for differences in locomotor behaviour (basal and morphine-induced, 10 mg/kg, s.c.) and opioid neurochemistry, propensity to self-administer morphine and cue-induced drug-seeking after abstinence. Blood analysis confirmed offspring exposure to naltrexone during gestation, birth and weaning. Naltrexone exposure increased litter size and reduced offspring birth-weight but did not alter brain morphometry. Compared to placebo, basal motor activity of naltrexone-exposed adult offspring was lower, yet they showed enhanced development of psychomotor sensitization to morphine. Developmental naltrexone exposure was associated with resistance to morphine-induced down-regulation of striatal preproenkephalin mRNA expression in adulthood. Adult offspring also exhibited greater operant responding for morphine and, in addition, cue-induced drug-seeking was enhanced. Collectively, these data show pronounced effects of developmental naltrexone exposure, some of which persist into adulthood, highlighting the need for follow up of humans that were exposed to naltrexone in utero.

Naltrexone depot formulations for opioid and alcohol dependence: a systematic review

Naltrexone is an opioid receptor antagonist that blocks the reinforcing effects of opioids and reduces alcohol consumption and craving. It has no abuse potential, mild and transient side effects, and thus appears an ideal pharmacotherapy for opioid dependence. Its effectiveness in alcohol dependence is less evident, but compliance with naltrexone combined with psychosocial support has been repeatedly shown to improve drinking outcomes. Limited compliance with oral naltrexone treatment is a known drawback. Several naltrexone implant and injectable depot formulations are being investigated and provide naltrexone release for at least 1 month. Studies among opioid-dependent patients indicate significant reductions in heroin use, but sample sizes are usually small. In alcohol dependence, two large multicenter trials report alcohol and craving reductions for naltrexone and placebo groups, indicating a significant but moderate effect. The pharmacokinetic profile of the injectable formulation indicates reliable naltrexone release over 1 month at therapeutic levels. Implant formulations releasing naltrexone up to 7 months are reported. Findings on safety and tolerability confirm the generally mild adverse effects described for naltrexone tablets. However, further research on therapeutic levels (i.e., opioid blocking) is warranted. The majority of naltrexone implants lacks approval for regular clinical use and larger longitudinal studies are needed. The available naltrexone depot formulations have the potential to significantly improve medication compliance in opioid and alcohol dependence. In certain circumstances, they may constitute a promising new treatment option.

Comparative treatment and mortality correlates and adverse event profile of implant naltrexone and sublingual buprenorphine

There is increasing interest in the use of implantable naltrexone as a new treatment for opiate dependence. This center has been one of the leaders in this form of treatment in Australia and has recently completed a registry-controlled review of our mortality data. As part of the study of the safety profile of this therapy, we were interested to review both the treatment correlates of previously presented mortality data and of adverse events. A total of 255 naltrexone implant therapy (NIT) and 2,518 buprenorphine (BUP) patients were followed for 1,322.22 and 8,030.02 patient-years, respectively. NIT patients had significantly longer days in treatment per episode (mean +/- standard deviation, 238.32 +/- 110.11 vs. 46.96 +/- 109.79), total treatment duration (371.21 +/- 284.64 vs. 162.50 +/- 245.76), and mean treatment times but fewer treatment episodes than BUP (all p < .0001). Serious local tissue reaction or infection each occurred in 1% of 200 NIT episodes. These data show that NIT economizes treatment resources without compromising safety concerns.

Improved parameters of metabolic glycaemic and immune function and arterial stiffness with naltrexone implant therapy

Here the dramatic and rapid response of a 54-year-old obese hypertensive man with poorly controlled insulin-dependent diabetes with a 33 year history of high dose heroin use, a 1 year history of refractory ulceration of his hands, ankles and feet, treated coronary artery disease, and the metabolic syndrome, to implantation with long-acting naltrexone implants is presented. In particular his hyperlipidaemia, hyperglycaemia, proinflammatory state, evidence of hepatic and renal insufficiency, arterial stiffness, and extensive and chronic cutaneous ulceration all improved dramatically over just 13 weeks, in association with complete control of his heroin, benzodiazepine, tobacco and cannabis use. The metabolic and vascular benefits were all highly statistically significant. The case is the first to document dramatic and rapid metabolic, immune and vascular improvements in association with clinical naltrexone therapy and are consistent with its likely effects in restoring addiction-related stem cell and immunological deficits.

The effects of maternally administered methadone, buprenorphine and naltrexone on offspring: review of human and animal data

Most women using heroin are of reproductive age with major risks for their infants. We review clinical and experimental data on fetal, neonatal and postnatal complications associated with methadone, the current "gold standard", and compare these with more recent, but limited, data on developmental effects of buprenorphine, and naltrexone. Methadone is a micro-opioid receptor agonist and is commonly recommended for treatment of opioid dependence during pregnancy. However, it has undesired outcomes including neonatal abstinence syndrome (NAS). Animal studies also indicate detrimental effects on growth, behaviour, neuroanatomy and biochemistry, and increased perinatal mortality. Buprenorphine is a partial micro-opioid receptor agonist and a kappa-opioid receptor antagonist. Clinical observations suggest that buprenorphine during pregnancy is similar to methadone on developmental measures but is potentially superior in reducing the incidence and prognosis of NAS. However, small animal studies demonstrate that low doses of buprenorphine during pregnancy and lactation lead to changes in offspring behaviour, neuroanatomy and biochemistry. Naltrexone is a non-selective opioid receptor antagonist. Although data are limited, humans treated with oral or sustained-release implantable naltrexone suggest outcomes potentially superior to those with methadone or buprenorphine. However, animal studies using oral or injectable naltrexone have shown developmental changes following exposure during pregnancy and lactation, raising concerns about its use in humans. Animal studies using chronic exposure, equivalent to clinical depot formulations, are required to evaluate safety. While each treatment is likely to have maternal advantages and disadvantages, studies are urgently required to determine which is optimal for offspring in the short and long term.

Sustained-release naltrexone for opioid dependence

BACKGROUND

Naltrexone is an opioid antagonist which effectively blocks heroin effects. Since opioid dependence treatment with naltrexone tablets suffers from high dropout rates, several depot injections and implants are under investigation. Sustained-release formulations are claimed to be effective, but a systematic review of the literature is lacking.

OBJECTIVES

To evaluate the effectiveness of sustained-release naltrexone for opioid dependence and its adverse effects in different study populations.

SEARCH STRATEGY

The following databases were searched from their inception to November 2007: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, LILACS, PsycINFO, ISI Web of Science, trial database at http://clinicaltrials.gov, available NIDA monographs, CPDD and AAAP conference proceedings. The reference lists of identified studies, published reviews and relevant web sides were searched manually. Study authors and drug companies were contacted to obtain any unpublished material or missing data.

SELECTION CRITERIA

To evaluate effectiveness only RCTs were included. To evaluate safety, any clinical trial reporting adverse effects was assessed. Treatment condition was extended to include alcohol dependent subjects and healthy volunteers.

DATA COLLECTION AND ANALYSIS

Reviewers independently evaluated the reports, rated methodological quality and extracted data. Analyses were performed separately for opioid dependent, alcohol dependent and healthy participants.

MAIN RESULTS

Foe effectiveness, one report met inclusion criteria. Two dosages of naltrexone depot injections (192 and 384 mg) were compared to placebo. High-dose significantly increased days in treatment compared to placebo (WMD 21.00, 95% CI 10.68 to 31.32, p<0.0001). High-dose compared to low-dose significantly increased days in treatment (WMD 12.00, 95% CI 1.69 to 22.31, p=0.02). Number of patients retained in treatment did not show significant differences between groups. For adverse effects, seventeen reports met inclusion criteria analyses, six were RCTs. Side effects were significantly more frequent in naltrexone depot groups compared to placebo. In alcohol dependent samples only, adverse effects appeared to be significantly more frequent in the low-dose naltrexone depot groups compared to placebo (RR 1.18, 95% CI 1.02 to 1.36, p=0.02). In the opioid dependent sample, group differences were not statistically significant. Reports on systematic assessment of side effects and adverse events were scarce.

AUTHORS' CONCLUSIONS

There is insufficient evidence to evaluate the effectiveness of sustained-release naltrexone for treatment of opioid dependence. For naltrexone injections, administration site-related adverse effects appear to be frequent, but of moderate intensity and time limited. For a harm-benefit evaluation of naltrexone implants, more data on side effects and adverse events are needed.

Pharmacological treatments for heroin and cocaine addiction

AIMS

To provide an overview of the pharmacological options for the treatment of heroin- and cocaine-dependent patients based on known biochemical pathways to addiction and the chronic disease model as a starting point for treatment planning.

RESULTS

Recent pre-clinical and clinical studies indicate that different brain structures and different neurotransmitters are involved in different stages of the addiction process. In addition, clinical experience shows that heroin and cocaine addiction can best be conceptualised and treated as a chronic, relapsing disorder with the following treatment goals: crisis intervention, cure or recovery (detoxification, relapse prevention) and care or partial remission (stabilization and harm reduction). The various high-quality studies, systematic literature reviews and formal meta-analyses clearly demonstrate that today many proven effective interventions are available for crisis intervention, detoxification, stabilization and harm reduction for heroin-dependent patients. Interventions directed at relapse prevention are still problematic and only effective in a minority of motivated patients in stable living conditions and adequate social support. In contrast, no proven effective pharmacological interventions are available for the treatment of cocaine-dependent patients, maybe with the exception of some patient groups that seem to benefit from treatment with disulfiram or amantadine. Treatment innovations are primarily based on experimental animal studies. Newly developed cannabinoid receptor antagonists and cortisol synthesis inhibitors show great promise.

CONCLUSION

Heroin addiction is a chronic relapsing disease that is difficult to cure, but stabilization and harm reduction can greatly increase the life time expectancy and the quality of life of the patient, his direct environment and society as a whole. Currently, no proven effective pharmacological interventions are available for cocaine addiction, and treatment has to rely on existing cognitive behaviour therapies combined with contingency management strategies.

Using naltrexone implants in the management of the pregnant heroin user

OBJECTIVES

To describe the case history and associated obstetric and neonatal outcomes of eight women who had their heroin dependency managed over pregnancy by naltrexone implant (two x 1.8 g of naltrexone embedded in poly-DL-lactide acid) treatment.

METHOD

Case data on maternal management associated with naltrexone implant were collected at the Australian Medical Procedures Research Foundation, Perth, Australia and three Perth hospitals.

RESULTS

Despite earlier instability on oral naltrexone and repeated relapses back to dependent heroin use these women, following treatment with naltrexone implant, remained heroin free throughout their pregnancies. Neonatal and obstetric outcomes were unremarkable.

CONCLUSIONS

This case series provides preliminary evidence that the pregnant heroin user can be managed by naltrexone implant without obvious risk to the mother or developing foetus. Importantly, the current case series suggests that the pregnant woman who finds it difficult to stabilise on oral naltrexone maintenance and returns to dependent heroin use may be managed using implantable naltrexone, thereby removing from her the onus for daily naltrexone medication compliance. The authors conclude that naltrexone implant may represent an important procedure for managing the pregnant heroin dependent patient who finds it difficult to shift away from her heroin use patterns. These preliminary findings require confirmation using a much larger controlled study.