Buprenorphine replacement therapy for adolescents with opioid dependence: early experience from a children's hospital-based outpatient treatment program

Opioid use by adolescents is on the rise and replacement therapy is an effective treatment. Methadone replacement has been used safely and effectively with adults, but methadone programs are often unattractive to teenagers. Buprenorphine is a new replacement therapy that has been shown to be as effective as high dose methadone and may be better suited for the treatment of younger patients. We describe the experiences of several adolescent patients who received treatment from an outpatient adolescent substance abuse program that operates within a children's hospital, with an emphasis on issues of adolescent development.

Emerging treatment modalities: balancing efficacy and safety

PURPOSE

The advantages and disadvantages of intravenous patient-controlled analgesia (i.v. PCA) and epidural analgesia are discussed. New approaches to the management of patients with acute post-operative pain are described. The results of controlled clinical trials with these modalities are presented.

SUMMARY

Intravenous patient-controlled analgesia, while effective, is a burdensome technology requiring approximately 125 steps and at least 6 staff members. Furthermore, medication and pump programming errors may lead to patient injury. Epidural analgesia via catheter has a high reported failure rate, causing analgesic gaps and requiring a high level of staff intervention. In a clinical trial involving hip arthroplasty, extended-release epidural morphine demonstrated a 48-hour duration of action with a marked reduction in need for supplemental analgesia. The fentanyl Iontophoretic Transdermal System has demonstrated therapeutic equivalence with morphine intravenous patient-controlled analgesia and similar safety. Selective opioid antagonists are under development that may selectively block gastrointestinal opioid receptors while preserving analgesia.

CONCLUSION

Recently approved agents and those in development may address a variety of unmet needs in the management of patients with post-operative pain.

Oral naltrexone as a treatment for relapse prevention in formerly opioid-dependent drug users: a systematic review and economic evaluation

OBJECTIVES

To investigate the clinical effectiveness and cost-effectiveness of naltrexone for relapse prevention in detoxified formerly opioid-dependent individuals compared with any strategy that does not use naltrexone, including treatment with placebo, other pharmacological treatments, psychosocial interventions or no treatment.

DATA SOURCES

Major electronic databases were searched from inception to September 2005.

REVIEW METHODS

Selected studies were screened and quality assessed. Meta-analyses were carried out as appropriate. A decision-analytic model using Monte Carlo simulation was developed that compared naltrexone as an adjunctive therapy to no naltrexone. It assumed compliance rates that were not enhanced by contingent management rewards (because this is current UK practice). Utility values could not be identified from the literature and so were obtained by research specially commissioned from the Value of Health Panel.

RESULTS

The methodological quality of the 26 randomised controlled trials (RCTs) that met the inclusion criteria was poor to moderate. The results suggest that naltrexone as maintenance therapy may be better than placebo in terms of retention in treatment, but this was not statistically significant. A meta-analysis of seven included RCTs gave the relative risk (RR) of loss of retention in treatment in the naltrexone arm as 0.94. The pooled hazard ratio (HR) reported in five of the RCTs for retention in treatment data followed up to 35 weeks was calculated as 0.90 in favour of naltrexone and also did not reach statistical significance. The risk of drug abuse in naltrexone versus placebo, with or without psychological support given in both arms, gave a pooled RR of 0.72, which was a statistically significant difference in favour of naltrexone. The pooled HR from three RCTs for opioid relapse-free rates was significantly different from placebo in favour of naltrexone 0.53; however, this fell off over time and may be of limited clinical significance. The RR of reimprisonment while on naltrexone therapy showed results in favour of naltrexone in the combined two studies of parolees or people on probation, but the number of participants was small. One study of 52 participants found that the difference in improvement score for risky sexual behaviour in the naltrexone group compared with the placebo group was not statistically significant. The adverse events data reported showed no significant difference between the naltrexone and placebo arms. The quality of the nine RCTs of interventions designed to increase retention with naltrexone was poor to moderate; however, all three different modalities of enhanced care showed some evidence of effectiveness. All of the contingency management programmes used incentive vouchers; the mean duration of treatment retention was 7.4 weeks for the contingency management intervention compared with 2.3-5.6 weeks for the naltrexone treatment alone. The mean length of time for which patients stayed on naltrexone was 84-103 days with additional psychosocial therapy compared with 43-64 days for the control group. In trials with added pharmacological agents the RRs of stopping treatment were 1.63 at 6 months and 1.31 at 12 months (in favour of naltrexone plus fluoxetine). It became statistically significant at 6 months, but not at 12 months. A meta-analysis of the RR of stopping treatment at week 12 (the minimum follow-up period) was carried out using six of the nine studies. The pooled RR of stopping treatment was 0.81. The results indicated that overall the intervention groups had 19% fewer patients who stopped treatment compared with the control group, but there was only a small number of studies and their quality was relatively poor. No existing economic evaluations were identified. The point estimate for the cost-effectiveness of naltrexone was pound42,500 per quality-adjusted life-year (QALY). Sensitivity analysis was carried out and the incremental cost-effectiveness ratio varied between pound34,600 and pound42,500 per QALY gained.

CONCLUSIONS

Following successful withdrawal from opioids, naltrexone may be administered on a chronic basis to block any future effects of opioids. Naltrexone appears to have some limited benefit in helping formerly opioid-dependent individuals to remain abstinent, although the quality of the evidence is relatively poor and heterogeneous. The limited quality and extent of the studies precluded an analysis of subgroups likely to benefit from naltrexone prescribing. Oral naltrexone is used infrequently in current UK practice, and this review suggests that this is appropriate as there is little evidence to support its wider implementation. There is an important deficit in information about the quality of life of people who use illicit opioids and this would perhaps be a worthwhile area of research in informing policy questions about the cost-effectiveness of different programmes and interventions.

Buprenorphine treatment: factors and first-hand experiences for providers to consider

The viability of using buprenorphine to treat opiate dependence was well documented prior to federal approval in October 2002. What has been lacking in the literature is "hands-on" experience of providers from a clinical management and practice management perspective. This article adds to the knowledge base by providing information about buprenorphine treatment as well as anecdotes from patients treated by the authors, leading to a detailed list of factors worth considering for the treatment provider contemplating adding an opiate-addicted population to an existing treatment base.

Buprenorphine substitution treatment in France: drug users' views of the doctor-user relationship

The French system for drug substitution, or maintenance treatment, established in 1996, differs from the often strict conditions attached to methadone clinics in other countries. Because of the predominant role of general practitioners and the flexible prescription rules for Subutex in France, the relationship between the physician and the drug user becomes a central element in the treatment. This article deals with the expectations that these users have of the physician, and their perception of his or her attitude towards them. In order to identify possible reasons for the absence of treatment compliance and of Subutex misuse, it focuses on the users' assessment of the physician's response to the problems they report. This study, based on a diversified convenience sample of 28 persons (19 men, 9 women) in treatment, showed 4 patterns of relationships between physicians and users, which differed in their focus: (1) closely focused on the posology of the prescription; (2) compliance with the prescribed regimen is the main issue in a relationship dominated by the physician; (3) an alliance between the physician and the user who is acknowledged as a person, and (4) a instrumental solely on the part of the user, who comes to procure a free, legal drug from a doctor's office. In all four case types, users had difficulty reporting other drug use or intravenous Subutex injection within this relationship, in which the stigma attached to drug dependence seems to reappear. Moreover, the lack of clarity about the treatment objectives and the time frame of the consultation limits the users' ability to integrate the treatment into their lives and to commit themselves to it. The heterogeneity and fragility of the users' situations, and the treatment objectives require regular assessment during contact with the physician. This constant reappraisal of the situation with the physician should help to optimize the treatment and avoid the hiatus that can generate or continue "misuse."

In-patient detoxification procedures, treatment retention, and post-treatment opiate use: comparison of lofexidine + naloxone, lofexidine + placebo, and methadone

OBJECTIVE

In-treatment and post-treatment outcomes were compared for three detoxification procedures (lofexidine+naloxone, lofexidine+placebo naloxone, and methadone). SAMPLE AND DESIGN: The sample was 137 opiate dependent in-patients. Detoxification treatments were 6-day lofexidine+naloxone (n=45), lofexidine+placebo naloxone (n=46), or 10-day methadone reduction (n=46). A cohort study design was used with double-blind random allocation to lofexidine+naloxone versus lofexidine+placebo. Patients who did not consent to, or who were excluded from randomisation received methadone.

RESULTS

Outcome differences between treatment groups at follow-up were generally associated with length of stay post-detoxification rather than detoxification procedure. Among patients who were not opiate abstinent throughout follow-up (n=85), those who received lofexidine+naloxone detoxification reported a longer interval to first heroin use, with an interaction between detoxification medication and subsequent retention in treatment also identified.

CONCLUSIONS

Detoxification medication may influence medium-term opiate use outcomes via its effect upon retention in treatment.

Distinct patterns of neural activation associated with ethanol seeking: effects of naltrexone

BACKGROUND

Alcoholism, like other substance abuse disorders, is a chronically relapsing condition. Compared with other abused drugs, however, little is known about the neural mechanisms mediating ethanol (EtOH)-craving and -seeking behavior leading to relapse. This study, therefore, was conducted to identify candidate brain regions that are recruited by an EtOH-associated contextual stimulus (S(+)). A secondary objective was to determine whether EtOH S(+)-elicited neural recruitment patterns are modified by the opiate antagonist naltrexone (NTX), a compound that reduces cue-induced craving in alcoholics and attenuates ethanol seeking in animal models of relapse.

METHODS

Rats were tested in a conditioned reinstatement model of relapse with subsequent examination of brain c-fos expression patterns elicited by an EtOH S(+) versus a cue associated with nonreward (S(-)). In addition, modification of these expression patterns by NTX was examined.

RESULTS

The EtOH S(+) reinstated extinguished responding and increased c-fos expression within the prefrontal cortex, hippocampus, nucleus accumbens, and hypothalamic paraventricular nucleus (PVN). Naltrexone suppressed the S(+)-induced reinstatement and attenuated hippocampal CA3 c-fos expression, while increasing neural activity in the extended amygdala and PVN.

CONCLUSIONS

Ethanol-associated contextual stimuli recruit key brain regions that regulate associative learning, goal-directed behavior, and Pavlovian conditioning of emotional significance to previously neutral stimuli. In addition, the data implicate the hippocampus, amygdala, and PVN as potential substrates for the inhibitory effects of NTX on conditioned reinstatement.

Overcoming policy and financing barriers to integrated buprenorphine and HIV primary care

Treatment for substance abuse and human immunodeficiency virus (HIV) infection historically have come from different providers, often in separate locations, and have been reimbursed through separate funding streams. We describe policy and financing challenges faced by health care providers seeking to integrate buprenorphine, a new treatment for opioid dependence, into HIV primary care. Regulatory challenges include licensing and training restrictions imposed by the Drug Addiction Treatment Act of 2000 and confidentiality regulations for alcohol and drug treatment records. Potential responses include the development of local training programs and electronic medical records. Addressing the complexity of funding sources for integrated care will require administrative support, up-front investments, and federal and state leadership. A policy and financing research agenda should address evidence gaps in the rationales for regulatory restrictions and should include cost-effectiveness studies that quantify the "value for money" of investments in integrated care to improve health outcomes for HIV-infected patients with opioid dependence.

Interactions between buprenorphine and antiretrovirals. I. The nonnucleoside reverse-transcriptase inhibitors efavirenz and delavirdine

This study examined drug interactions between buprenorphine, an opioid partial agonist medication used in the treatment of opioid dependence, and the nonnucleoside reverse-transcriptase inhibitors (NNRTIs) efavirenz (EFV) and delavirdine (DLV). Opioid-dependent, buprenorphine/naloxone-maintained, human immunodeficiency virus (HIV)-negative volunteers (n=10 per NNRTI) participated in 24-h sessions to determine pharmacokinetics of buprenorphine and of buprenorphine with either EFV or DLV after administration of standard doses of either antiretroviral for 15 or 7 days, respectively. Opiate withdrawal symptoms, cognitive effects, and adverse events were determined before and after antiretroviral administration in opioid-dependent participants. The pharmacokinetics of NNRTIs in healthy control participants were used to determine the effect of buprenorphine on NNRTIs. EFV decreased the buprenorphine area under the concentration-time curve (P<.001). DLV increased buprenorphine concentrations (P<.001). Clinically significant consequences of these interactions were not observed. Buprenorphine did not alter antiretroviral pharmacokinetics. Adjustments of doses of either buprenorphine or EFV or DLV are not likely to be necessary when these drugs are administered for the treatment of opiate dependence and HIV disease.

Initial strategies for integrating buprenorphine into HIV care settings in the United States

The Centers for Disease Control and Prevention's HIV Prevention Strategic Plan Through 2005 advocated for increasing the proportion of persons with human immunodeficiency virus (HIV) infection and in need of substance abuse treatment who are successfully linked to services for these 2 conditions. There is evidence that integrating care for HIV infection and substance abuse optimizes outcomes for patients with both disorders. Buprenorphine, a recently approved medication for the treatment of opioid dependence in physicians' offices, provides the opportunity to integrate the treatment of HIV infection and substance abuse in one clinical setting, yet little information exists on the models of care that will most successfully facilitate this integration. To promote the uptake of this type of integrated care, the current review provides a description of 4 recently implemented models for combining buprenorphine treatment with HIV primary care: (1) an on-site addiction/HIV specialist treatment model; (2) a HIV primary care physician model; (3) a nonphysician health professional model; and (4) a community outreach model.

The potential role of buprenorphine in the treatment of opioid dependence in HIV-infected individuals and in HIV infection prevention

Untreated opioid dependence is a major obstacle to the successful treatment and prevention of human immunodeficiency virus (HIV) infection. In this review, we examine the interwoven epidemics of HIV infection and opioid dependence and the emerging role of buprenorphine in improving HIV treatment outcomes among infected individuals, as well as its role in primary and secondary prevention. This article addresses some of the emerging issues about integrating buprenorphine treatment into HIV clinical care settings and the various strategies that must be considered. Specifically, it addresses the role of buprenorphine in improving HIV treatment outcomes through engagement in care, access to antiretroviral therapy and preventive therapies for opportunistic infections, and the potential benefits of and pitfalls in integrating buprenorphine into HIV clinical care settings. We discuss the key research questions regarding buprenorphine in the area of improving HIV treatment outcomes and prevention, including a review of published studies of buprenorphine and antiretroviral treatment and currently ongoing studies, and provide insight into and models for integrating buprenorphine into HIV clinical care settings. Dialogue among practitioners and policy makers in the HIV care and substance abuse communities will facilitate an effective expansion of buprenorphine and ensure that these beneficial outcomes are achieved.

Interactions between buprenorphine and antiretrovirals. II. The protease inhibitors nelfinavir, lopinavir/ritonavir, and ritonavir

We examined drug interactions between buprenorphine, an opioid partial agonist available by prescription for treatment of opioid dependence, and the protease inhibitors (PIs) nelfinavir (NFV), ritonavir (RTV), and lopinavir/ritonavir (LPV/R). Opioid-dependent, buprenorphine/naloxone-maintained, human immunodeficiency virus (HIV)-negative volunteers (n=10 per PI) participated in 24-h pharmacokinetic studies, before and after administration of each PI. Symptoms of opiate withdrawal and excess were determined before and after PI administration. PI pharmacokinetics were determined and compared between opiate-dependent participants and healthy control participants (n=15 per PI). Administration of RTV, but not of NFV or LPV/R, resulted in a significant increase in the buprenorphine area under the concentration-time curve (AUC). Symptoms of opiate excess, however, were not observed. Buprenorphine had no significant effects on PI AUC. Adjustments of doses of either buprenorphine or NFV, LPV/R, or RTV are not likely to be necessary when these drugs are administered for the treatment of opioid dependence and HIV disease.

Predictors of retention in naltrexone maintenance for opioid dependence: analysis of a stage I trial

Behavioral naltrexone therapy (BNT) was developed to address the shortcomings of naltrexone maintenance for opiate dependence and improve compliance by integrating several empirically validated methods, including the use of a significant other to monitor compliance, voucher incentives, and motivational techniques. An uncontrolled Stage I pilot trial (N = 47) of BNT was conducted. Baseline demographic and clinical variables were evaluated as predictors of retention with univariate tests. Significant predictors were entered together into a multiple regression model. Poorer (shorter) retention in treatment was associated with methadone use and higher average bags per day of heroin. Other variables that became non-significant in multiple regression analysis included older age and depressive symptoms. Individuals with greater physiologic dependence and/or dependence on longer-acting opiates are at higher risk to drop out from naltrexone maintenance and may require a more gradual detoxification and more intensive behavioral therapy aimed at enhancing initial compliance.

High and low dosage oxcarbazepine versus naltrexone for the prevention of relapse in alcohol-dependent patients

INTRODUCTION

Oxcarbazepine (OXC) reduces high-voltage-activated calcium currents, thus reducing glutamatergic transmission at corticostriatal synapses. This effect on NMDA glutamatergic transmission may play a role against the increased glutamatergic transmission determined by alcohol withdrawal. To investigate the efficacy and safety of OXC in relapse prevention we compared OXC at different dosages with Naltrexone (NAL) in a 90 days randomised open-label trial. Craving and psychiatric symptoms improvements were the secondary endpoints.

METHODS

Eighty-four detoxified alcohol dependent subjects currently meeting clinical criteria for alcohol dependence were randomised into three groups: 27 patients received 50 mg of naltrexone, 29 received 1500-1800 mg of oxcarbazepine (OXC high), 28 patients 600-900 mg of oxcarbazepine (OXC low). Craving (VAS; OCDS) and withdrawal (AWRS) rating scales were applied; psychiatric symptoms were evaluated through the SCL-90-R.

RESULTS

A significantly larger number of subjects remained alcohol free in the OXC high group (58.6%) with respect to both the OXC low (42.8%) and the NAL groups (40.7%). Comparing the OCDS total scores at the end of the treatment, the improvement was significantly greater for the NAL group with respect to the OXC low group. The reduction of the Hostility-Aggression subscore of the SCL-90-R was significantly greater in the OXC high group than that of the other groups. Dual diagnosis patients had a better outcome when treated with OXC high.

DISCUSSION

OXC at a dosage of 1500-1800 mg/day might be beneficial in terms of alcohol relapse prevention. The low dosage formulation did not show the same trend, but it still remain in the same range as NAL. The mechanism involved in the efficacy of oxcarbazepine in relapse prevention could be less related to craving and more connected to the treatment of the comorbid psychiatric symptomatology and the alcohol protracted withdrawal syndrome.

Stress and drug-cue-induced craving in opioid-dependent individuals in naltrexone treatment

BACKGROUND

Naltrexone is a nonaddictive medication that blocks the euphoric effects of opioids. However, naltrexone treatment is associated with high rates of noncompliance and opioid relapse, possibly because it does not reduce stress and protracted withdrawal symptoms during early recovery. Prior clinical and preclinical research has indicated that both stress and drug-cue-related arousal response is associated with craving and vulnerability to relapse in a range of drug-using populations.

AIMS

To examine opioid craving and the subjective and cardiovascular response to stress and drug cues in naltrexone-treated opioid abusers.

METHOD

Eleven men and three women engaged in naltrexone treatment for opioid dependence. They were exposed to personalized stress, drug-cue, and neutral-relaxing imagery in a single laboratory session. Subjective (craving, emotion) and cardiovascular (heart rate, systolic blood pressure, and diastolic blood pressure) measures were assessed.

RESULTS

Stress and drug-cue-related imagery significantly increased opioid craving, anxiety, and negative emotions and significantly decreased positive emotions compared to neutral imagery. Selective emotional responses were greater in the stress condition than in the drug-cue condition. Only stress-related imagery was associated with an increased cardiovascular response.

CONCLUSIONS

Naltrexone-treated opioid abusers demonstrate vulnerability to stress and drug-cue-induced craving and arousal responses that may contribute to the high rates of noncompliance and relapse among opioid-dependent individuals undergoing naltrexone treatment. Pharmacological and behavioral interventions that specifically target the negative affectivity that co-occurs with drug-cue and stress-induced craving could be of benefit in improving naltrexone treatment outcomes in opioid dependence.

Naltrexone and disulfiram in patients with alcohol dependence and current depression

OBJECTIVE

Although disulfiram and naltrexone have been approved by the Food and Drug Administration for the treatment of alcoholism, no medications have been approved for individuals with alcohol dependence and comorbid psychiatric disorders. In particular, the effect of these medications on alcohol use outcomes and on specific psychiatric symptoms is still unknown in patients with the most common co-occurring disorder, major depression.

METHOD

Two hundred fifty-four patients with a major Axis I psychiatric disorder and comorbid alcohol dependence were treated for 12 weeks in an outpatient medication study conducted at 3 Veterans Administration outpatient clinics. Randomization included (1) open randomization to disulfiram or no disulfiram, and (2) double-blind randomization to naltrexone or placebo. This resulted in 4 groups: (1) naltrexone alone, (2) placebo alone, (3) disulfiram and naltrexone, and (4) disulfiram and placebo. Primary outcomes were measures of alcohol use. Secondary outcomes included psychiatric symptoms assessed by the Hamilton Depression Rating Scale, alcohol craving, gamma-glutamyltransferase levels, and adverse events.

RESULTS

One hundred thirty-nine subjects (54.7%) met the current Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for major depression. There was no relationship between the diagnosis of depression and medication treatment on alcohol use outcomes, psychiatric symptoms, or the reporting of side effects for these medications. There was a significant interaction between diagnosis, medication group, and craving, where subjects with depression on disulfram reported lower craving over time than subjects with depression on naltrexone.

CONCLUSIONS

The results suggest that disulfiram and naltrexone are safe pharmacotherapeutic agents for dually diagnosed individuals with depression for the treatment of alcohol use disorders.

Comparison of buprenorphine and methadone in the treatment of opiate withdrawal: possible advantages of buprenorphine for the treatment of opiate-benzodiazepine codependent patients?

The study is a preliminary investigation to compare the effectiveness of buprenorphine and methadone as opiate detoxification treatments. The sample comprised 123 drug misusers who were dependent upon opiates only or who were codependent upon opiates and benzodiazepines. Drug misusers dependent upon methadone doses up to 70 mg were eligible for the study. Detoxification took place within a specialist inpatient drug-dependence unit. Withdrawal symptom severity was assessed on a daily basis by means of the Short Opiate Withdrawal Scale. Outcome was assessed for reductions in severity of withdrawal symptoms, treatment retention, and treatment completion. Buprenorphine detoxification was associated with less severe opiate withdrawal symptoms than methadone. Opiate/Benzodiazepine codependent patients reported less severe withdrawal symptoms during treatment with buprenorphine than with methadone and were also more likely to complete detoxification when treated with buprenorphine.

Treatment of opioid-induced gut dysfunction

Opioid analgesics are the mainstay in the treatment of moderate-to-severe pain, yet their use is frequently associated with adverse effects, the most common and debilitating being constipation. Opioid-induced motor stasis results from blockade of gastrointestinal peristalsis and fluid secretion, and reflects the action of the endogenous opioid system in the gut. Methylnaltrexone and alvimopan are new investigational drugs that selectively target peripheral mu-opioid receptors because they are poorly absorbed in the intestine and do not enter the brain. Clinical studies have proved the concept that these drugs prevent opioid-induced bowel dysfunction without interfering with analgesia. As reviewed in this article, opioid receptor antagonists with a peripherally restricted site of action also hold therapeutic promise in postoperative ileus and chronic constipation due to the fact that they have been found to stimulate intestinal transit.

Role of opioid antagonists in the treatment of women with glucoregulation abnormalities

Beta-endorphin were detected in the endocrine pancreas and seem able to influence insulin and glucagon release. Hence, endogenous opioids could have a role in glucoregulation and in the pathogenesis of obesity beyond the previously detected effects on appetite. Metabolic abnormalities, such as hyperinsulinemia, insulin-resistance and obesity, are common features of polycystic ovary syndrome (PCOS), and seem to have a pathogenetic role in this disorder. A link between opioids and PCOS-related hyperinsulinism is suggested by the finding of altered central opioid tone and elevated beta-endorphins levels, directly correlated with body weight, in these patients. Furthermore, naloxone and naltrexone significantly reduce the insulin response to glucose load only in hyperinsulinemic PCOS patients. This effect is obtained chiefly through an improvement of insulin clearance. Naltrexone is also able to ameliorate the abnormal gonadotrophins secretion and to improve the ovarian responsiveness in obese PCOS women undergoing ovulation induction with exogenous GnRH. Such effects are believed to be obtained through an amelioration of hyperinsulinemia. Gonadal steroids modulate the opioid system both centrally and in peripheral districts. Nevertheless, the decline of ovarian function does not abolish the opioidergic control of glucoregulation. Post-menopausal period is characterised by a high prevalence of hyperinsulinemia and insulin-resistance. In particular, an association between hyperinsulinemia and increased opioid activity was found in postmenopausal women showing a central body fat distribution. Both naloxone and naltrexone ameliorate the metabolic imbalance also when it appears in the climacteric period, and mainly by increasing insulin clearance. The benefits of naltrexone may represent in the future a useful tool for the treatment of women with hyperinsulinism in the clinical practice.

Reversal of opioid-induced bladder dysfunction by intravenous naloxone and methylnaltrexone

Peripheral mechanisms may be involved in opioid actions on the urinary bladder. This double-blind study investigated whether opioid inhibition of bladder function is reversed by methylnaltrexone, a peripheral opioid antagonist. Thirteen healthy male volunteers received an intravenous (i.v.) infusion of remifentanil, 0.15 mcg/kg/min, then a single i.v. dose of study medication (methylnaltrexone 0.3 mg/kg, naloxone 0.01 mg/kg, or saline). Urodynamics were measured with indwelling bladder and rectal catheters, and pupil size was assessed with infrared pupillometry. Remifentanil decreased detrusor pressure in 21/25 sessions and caused complete urinary retention in 18/25. Voiding was possible in 7/7, 5/12, and 0/6 sessions after naloxone, methylnaltrexone, and saline, respectively (P=0.0013). Remifentanil caused marked miosis that was reversed by naloxone, but not methylnaltrexone or placebo (P<0.0001). The pupil data confirm that methylnaltrexone did not reverse central opioid effects. Reversal of urinary retention by methylnaltrexone indicates that peripheral mechanisms may play a role in opioid-induced bladder dysfunction.

The opioid receptor antagonist, naloxone, protects spinal motor neurons in a murine model of alphavirus encephalomyelitis

Spread of neuroadapted Sindbis virus (NSV) to motor neurons (MN) of the spinal cord (SC) causes severe hind limb weakness in C57BL/6 mice and models the paralysis that can accompany alphavirus and flavivirus encephalomyelitis in humans. The fate of spinal MN dictates the severity of NSV-induced paralysis, and recent data suggest that MN damage can occur indirectly via the actions of activated microglial cells. Because the opioid receptor antagonist, naloxone (NAL), blocks microglial-mediated neurodegeneration in other models, we examined its effects during NSV infection. Drug treatment prevented paralysis and enhanced the survival of MN without altering NSV tropism, replication, or clearance from SC tissue. Further studies showed that NAL most effectively inhibited paralysis in a 72-h window after NSV challenge, suggesting that the drug inhibits an early event in SC pathogenesis. Histochemical studies demonstrated that NAL blocked early microglial activation in SC tissue sections, and protein assays showed that the early induction of pathogenic IL-1 beta was blunted in SC homogenates. Finally, loss of glutamate transporter-1 (GLT-1) expression in SC, an astrocyte glutamate reuptake protein responsible for lowering toxic extracellular levels of glutamate and preventing MN damage, was reversed by NAL treatment. This GLT-1 loss proved to be highly IL-1 beta-dependent. Taken together, these data suggest that NAL is neuroprotective in the SC by inhibiting microglial activation that, in turn, maintains normal astrocyte glutamate homeostasis. We propose that drugs targeting such microglial responses may have therapeutic benefit in humans with related viral infections.