Naltrexone Placebo Research Articles

Exploring genetic predictors of naltrexone treatment response in opioid use disorder

Purpose: The present study was aimed to evaluate the effect of the opioid receptors genes and dopamine system genes polymorphisms on the treatment outcomes of opioid dependence with implantable and oral naltrexone in randomized double blinded double dummy placebo controlled clinical trial. Methods: 306 patients with opioid dependence were randomized in 3 treatment groups (102 ss in each). The first group received implantation of 1000 mg naltrexone every 2 months during the 6 months period + oral naltrexone placebo; the second group — placebo implant every 2 months + oral naltrexone (50mg/day), and the third group — placebo implant + oral naltrexone placebo. All enrolled participants provided blood sample at baseline for genetic analysis of polymorphisms in following genes: mu-opioid receptor (OPRM1), kappa-opioid receptor (OPRK1), catechol-O-methyltransferase (COMT), dopamine receptors types 2 (DRD2) and 4 (DRD4), dopamine-beta-hydroxylase, and dopamine transporter (DAT1). Results: Regardless of provided treatment several polymorphisms of tested genes were associated with high risk of relapse: allele L (2R) DRD4 120bp (p=0.05; OR(95% CI)=3.3(1.1-10.1) ); allele С DRD2 NcoI (р=0,051 OR(95% CI) = 2,86 (1,09 — 7,52); genotype 9.9 DAT VNTR40bp (р=0,04; RR(95% CI) = 1,4(1,3 — 1,5)); on the contrary variants of polymorphisms (СС+СТ)-(ТТ)) of genes (OPRK1- DRD2Ncol) increased the chance to complete the treatment program (р=0,004; OR(95% CI) = 7.4 (1.8 — 30.4)), Kaplan-Meier survival analysis, р=0,016). The probability of completing treatment program by carriers of all these above mentioned variants of polymorphisms (OPRK1DRD2Ncol) was higher for oral naltrexone group (p=0.016), lower for double placebo group (p=0.015), but did not influence treatment outcomes in naltrexone-implant group. Conclusion: Naltrexone-implant is an effective medication for treatment of opioid dependence and its effectiveness exceeds oral naltrexone and placebo. The study showed joint influence of opioid receptor genes and genes of dopaminergic system on the treatment outcomes of opioid dependence. Genetic analysis is useful for determining potential responders to naltrexone treatment of opioid dependence.

Slow-release naltrexone implant versus oral naltrexone for improving treatment outcomes in people with HIV who are addicted to opioids: a double-blind, placebo-controlled, randomised trial

Untreated opioid addiction in people with HIV is associated with poor HIV treatment outcomes. Slow-release, long-acting, implantable naltrexone might improve these outcomes. Here, we present results of a study aimed to test this hypothesis. We did a 48 week double-blind, double-dummy, placebo-controlled, phase 3, randomised trial with men and women addicted to opioids who were starting antiretroviral therapy (ART) for HIV and whose viral loads were higher than 1000 copies per mL. Participants were seeking treatment at two HIV and two narcology programme centres in Saint Petersburg, Russia, and the surrounding Leningrad region. The Pavlov statistical department created a table with stratification on gender distribution, viral load, and CD4 cell count. We stratified participants according to gender, viral load, and CD4 cells per μL, and randomly assigned (1:1) them to addiction treatment with a naltrexone implant and oral naltrexone placebo (implant group) or oral naltrexone and placebo implant (oral group). The primary outcome was plasma viral load of less than 400 copies per mL at 24 weeks and 48 weeks. We included all randomly assigned participants in outcome analyses (intention to treat). Treatment staff and patients were masked to group assignment. The study is complete and registered at ClinicalTrials.gov, NCT01101815. Between July 14, 2011, and April 14, 2014, 238 potential participants were recruited and screened, 35 were excluded for not meeting inclusion criteria, three declined to participate, and 200 were randomly assigned to treatment (100 to each group). At week 24, 38 (38) participants in the implant group and 35 (35%) in the oral group had viral loads less than 400 copies per mL (risk ratio 1·1, 95% CI 0·76-1·56; p=0·77). At week 48, 66 participants in the implant group and 50 in the oral group had viral loads less than 400 copies per mL (risk ratio 1·32, 95% CI 1·04-1·68; p=0·045). There were seven serious adverse events: three deaths in the implant group (one due to heart disease, one trauma, and one AIDS), and four in the oral group (two overdoses, one pancreatic cancer, and one AIDS). The overdose deaths occurred 9-10 months after the last naltrexone dose. The longer the blockade of opioid effects, the more protection an individual gets from missed ART doses and impulsive behaviours that lead to relapse and poor, even fatal, outcomes. Commercial development of implants could result in a meaningful addition to addiction treatment options. National Institutes of Health, National Institute on Drug Abuse, Penn Centre for AIDS Research, and Penn Mental Health AIDS Research Centre.

Slow Release Naltrexone Implant vs Oral Naltrexone for Improving Treatment Outcomes in Opioid Addicted Participants with HIV: A Randomised Trial

Background: Untreated opioid addiction in persons with HIV is associated with poor outcome. Agonist maintenance is not always available and some do not want it. Slow release naltrexone may be a useful option. Methods: The study was a 48-week trial in which 200 opioid addicted patients starting antiretroviral treatment (ART) for HIV were stratified according to gender, viral load (VL) and CD4 count, and randomized to addiction treatment using a naltrexone implant and oral naltrexone placebo (NI; n=100), or oral naltrexone 50 mg/day and a placebo implant (ON; n=100). Research staff was blinded to group assignment. Primary outcome was plasma VL<400 copies at 24 and 48 weeks. All participants were included in the outcome analyses according to intention to treat principles. Findings: There was no difference between NI and ON in the number of participants with VL<400 copies at week 24 (38 [38%] vs 35 [35%] p=0*77) but more NI than ON participants had a VL<400 copies at week 48 (66 [66%] vs 50 [50%] RR: 1*32 [95% CI: 1*04-1*68] p=0*0451). Regardless of group assignment, those who continued naltrexone at 24 weeks more commonly had VL<400 copies than discontinuers (51 [70 %] vs 22 [30%] RR: 2*89 [95% CI: 1*91-4*38] p<0*0001) with similar findings at week 48 (VL <400 copies (64 [55%] vs 52 [44%] RR: 1*53 [95% CI: 1*21-1*95] p=0*0005). There were seven serious adverse events registered: three deaths in NI (one heart disease, one trauma, one AIDS), and four in ON (two overdoses, one pancreatic cancer, one AIDS). The overdose deaths occurred 9-10 months after the last naltrexone dose. Interpretation: An implant that is approved in the Russian Federation and provides opioid blockade for three months caused no serious adverse events and improved retention and outcome of persons with opioid addiction and HIV. Clinical Trial Number: The trial is registered at ClinicaTrials.gov, NCT02046252. Funding Statement: NIDA Grants: R01 DA026336; K05 DA17009; U10 DA013043; UG1 DA013034; Penn Center for AIDS Research P30 A1045008; Penn Mental Health AIDS Research Center P30 MH097488 Declaration of Interests: Fidelity Capital provided Prodetoxon®) at a reduced price and Prodetoxon placebo at no charge. Dr. Woody is a consultant to BICX102, a company that submitted a grant to NIDA requesting funds to develop and test a similarly-designed implant that could be submitted to the FDA for approval in the U.S. Dr. Krupitsky was a consultant to Alkermes in 2008-2011 and was a consultant for Prodetoxon LTD in 2017. Ethics Approval Statement: The protocol and consents were written in English, translated into Russian, reviewed by bilingual staff in Russia and the U.S, and approved by human subjects’ committees (IRBs) at First Pavlov State Medical University and the University of Pennsylvania. The sponsor and the two IRBs did annual reviews of study progress and reports of adverse events.

Outpatient transition to extended-release injectable naltrexone for patients with opioid use disorder: A phase 3 randomized trial

BackgroundInjectable extended-release naltrexone (XR-NTX), approved to prevent relapse to opioid dependence, requires initial abstinence. This multisite outpatient clinical trial examined the efficacy and safety of low-dose oral naltrexone (NTX), combined with a brief buprenorphine (BUP) taper and standing ancillary medications, for detoxification and induction onto XR-NTX. MethodsPatients (N = 378) were randomized, stratified by primary short-acting opioid-of-use, to one of three regimens: NTX + BUP; NTX + placebo BUP (PBO-B); placebo NTX (PBO-N) + PBO-B. Patients received 7 days of ascending NTX or placebo, concurrent with a 3-day BUP or placebo taper, and ancillary medications in an outpatient setting. Daily psychoeducational counseling was provided. On Day 8, patients passing a naloxone challenge received XR-NTX. ResultsRates of transition to XR-NTX were comparable across groups: NTX/BUP (46.0%) vs. NTX/PBO-B (40.5%) vs. PBO-N/PBO-B (46.0%). Thus, the study did not meet its primary endpoint. Adverse events, reported by 32.5% of all patients, were mild to moderate in severity and consistent with opioid withdrawal. A first, second, and third XR-NTX injection was received by 44.4%, 29.9%, and 22.5% of patients, respectively. Compared with the PBO-N/PBO-B group, the NTX/BUP group demonstrated higher opioid abstinence during the transition and lower post-XR-NTX subjective opioid withdrawal scores. ConclusionsA 7-day detoxification protocol with NTX alone or NTX + BUP provided similar rates of induction to XR-NTX as placebo. For those inducted onto XR-NTX, management of opioid withdrawal symptoms prior to induction was achieved in a structured outpatient setting using a well-tolerated, fixed-dose ancillary medication regimen common to all three groups.

A pharmacogenetic analysis of dopaminergic and opioidergic genes in opioid addicts treated with the combination of naltrexone and guanfacine

To evaluate an effect of opioid receptor and dopamine system gene polymorphisms on the efficacy of combined treatment with oral naltrexone and guanfacine in a randomized double blinded double dummy placebo controlled clinical trial. Three hundred and one patients with opioid dependence were randomized into 4 treatment groups: naltrexone 50 mg/day + guanfacine 1 mg/day (N+G); naltrexone + placebo guanfacine (N+GP); placebo naltrexone + guanfacine (NP+G); double placebo (NP+GP). The primary outcome was treatment retention. All enrolled participants were genotyped for polymorphisms in the following genes: mu- (OPRM1), kappa-opioid receptors (OPRK1), catechol-O-methyltransferase (COMT), dopamine receptors types 2 (DRD2) and 4 (DRD4), dopamine-beta-hydroxylase, and dopamine transporter (SLC6A3, DAT1) and alpha-2-adrenoreceptor (ADRA2A) a pharmacological target of guanfacine. The efficacy of the combination of naltrexone and guanfacine was comparable to naltrexone monotherapy. Regardless of treatment, several gene polymorphisms were associated with higher chance to complete the treatment program: allele Т DRD4 - 521 С/Т (rs1800955) (р=0.039; OR (95% CI)=3.7 (1.1-12.7); log-rank test: р=0.01); allele С DRD2 С957Т (rs6277) (р=0.03; HR=0.6 (0.34-0.95); genotype combination: DRD4 VNTR (LL) + OPRM1 A118G (rs1799971) (AA), р=0.051; DRD2 C957T (ТТ) + OPRM1 (rs1074287) (СС), р=0.025; DRD2 - 141С (II) + OPRM1 (rs510769) (АА), р=0.035; DBH Fau(СС) + OPRM1 (rs1074287) (СС), р=0.0497. Regardless of treatment several polymorphisms were associated with high risk of relapse: allele Т (rs510769) OPRM1 (р=0.053), allele А (rs1799971, A118G) OPRM1 (р=0.056), allele S exon III 48 bp DRD4 VNTR (р=0.001; HR=3.1 (ДИ 95% 1.57-6.18); genotype combinations: DRD4 - 521 С/Т (ТТ) + DRD2 Nco I (TT), р=0.026; DRD4 -521 С/Т (ТТ) + DRD2 -141 С (II), р=0.011; DRD4 - 521 С/Т (ТТ) + OPRM1 A118G (rs1799971) (AA), р=0.011; DRD2 Nco I(ТТ) + ADRA2A (СС), р=0.012; DRD2 Nco I(ТТ) + OPRM1 A118G (AA), р=0.02. The effects dependent on the treatment group were as follows: 1) in the N+G group, patients with the DRD4 -521 С/Т TT genotype had higher probability of completion of treatment program in comparison with other genotypes (CC and CT) (log-rank test: p=0.002); 2) in NP + GP group, patients with the OPRM1 rs510769 T allele had higher risk of relapse compared to the genotype GG (p=0.008) (FDR p<0.0125). The additive effect of opioid receptor genes and dopaminergic system genes on outcomes of treatment opioid dependence with oral naltrexone and guanfacine was shown. Pharmacological effects of naltrexone and guanfacine were associated with genetic variants of the DRD4 - 521C/T polymorphism, since its effect was shown only in the N+G group. The effect of the OPRM1 rs510769 polymorphism was demonstrated in the double placebo group that was associated with personality traits (temperament, character) and determined compliance. Genetic analysis is useful for determining potential responders to treatment of opioid dependence; genotyping can increase the efficacy of pharmacotherapy.

Differentiating the Effect of an Opioid Agonist on Cardiac Repolarization From µ-Receptor–mediated, Indirect Effects on the QT Interval: A Randomized, 3-way Crossover Study in Healthy Subjects

PurposeA thorough QT study was conducted in healthy subjects to evaluate the effect of buprenorphine hydrochloride administered through a buccal soluble film under coverage of naltrexone to block confounding, secondary QT effects. MethodsHealthy subjects were enrolled in a randomized, partially blinded, 4-way crossover designed study. Subjects received buprenorphine 3 mg with naltrexone, naltrexone alone (with placebo films), placebo (placebo films and placebo naltrexone), and open-label moxifloxacin 400 mg with placebo naltrexone in separate in-house treatment periods. Naltrexone treatment (50 mg) was initiated 12 hours before buprenorphine and was given every 12 hours for a total of 4 doses. ECG data were extracted from a continuous recording predose and serially after dosing on the treatment day. ECG intervals were measured at a central ECG laboratory by using the high-precision QT technique. The QT interval was corrected for heart rate with Fridericia’s formula (QTcF), and change-from-predose baseline QTcF (∆QTcF) was analyzed by using a mixed effect model. FindingsFifty-eight subjects (35 males) with a mean age of 32 were enrolled into the study. Treatment with buprenorphine 3 mg resulted in a small QT effect with the largest mean naltrexone-corrected ∆QTcF reaching 5.8 msec at 8 hours’ postdosing (upper bound of the 90% CI below 10 msec). Exposure response analysis with a linear model demonstrated a significant linear relationship between plasma levels and naltrexone-corrected ∆QTcF, with an estimated mean slope of 0.65 msec per nanogram/milliliter (90% CI, 0.22 to 1.08). Using the exposure response model, an effect on ∆QTcF of 4.5 msec (2.80 to 6.12) can be predicted at the observed geometric peak plasma level after administration of the 3-mg buprenorphine dose in this study (3.6 ng/mL [3.33 to 3.98]). Naltrexone alone did not have a relevant effect on the QTcF interval. ImplicationsThe present study showed that buprenorphine plasma levels up to 5 ng/mL had no effect on the QTc above the level of clinical concern.

A double-blind randomized placebo-controlled study of the efficacy of the combined treatment with naltrexone and guanfacine for relapse prevention in opiate dependence

Authors studied the effect of α-2-adrenoreceptor agonist guanfacine on replace prevention in opiate addicts. Three hundred and one recently detoxified opiate addicts were randomized under the double-blind double-dummy conditions into one of four treatment groups: naltrexone 50 mg/day+guanfacine 1 mg/day (N+G), naltrexone+guanfacine placebo (N+GP), naltrexone placebo+guanfacine (NP+G), and double placebo (NP+GP). The primary outcome was retention in treatment. The secondary outcomes were perceived stress (Perceived Stress Scale) and craving. At the end of six months, 20 (26.7%) patients in the N+G group and 15 (19.7%) (p=0.26 to N+G) in N+GP group were retained in treatment compared to 5 (6.7%) in the NP+G group (p=0.002 to N+G group and p=0.017 to N+GP group) and 8 (10.7%) in the double placebo group (p=0.013 to N+G group). There is no significant difference in retention between the N+G group and N+GP group at the end of treatment. Guanfacine had significant craving and stress reducing effect. Naltrexone was more effective than placebo for relapse prevention in opioid dependent patients. The efficacy of the combination of naltrexone and guanfacine was comparable to naltrexone alone. Guanfacine moderately reduced both stress and craving.

Stabilization of remission in patients with opioid dependence with naltrexone implant: a pharmacogenetic approach

To evaluate the effect of opioid receptor genes and dopamine system genes polymorphisms on treatment outcomes of opioid dependence with implantable and oral naltrexone. Authors carried out a randomized double-blind, double-dummy, placebo-controlled clinical trial. Three hundred and six patients with opioid dependence were randomized into 3 equal treatment groups. The first group received implantation of 1000 mg naltrexone every 2 months during 6 months + oral naltrexone placebo; the second group - placebo implant every 2 months + oral naltrexone (50mg/day) and the third group - placebo implant + oral naltrexone placebo. It was genotyped polymorphisms in the following genes: mu-opioid receptor (OPRM1), kappa-opioid receptor (OPRK1), catechol-O-methyltransferase (COMT), dopamine receptors types 2 (DRD2) and 4 (DRD4), dopamine-beta-hydroxylase, and dopamine transporter (DAT1). Regardless of treatment several polymorphisms of these genes were associated with high risk of relapse: an allele L (2R) DRD4 120bp (p=0.05; OR (95% CI)=3.3(1.1-10.1)); an allele С DRD2 NcoI (р=0,051; OR (95% CI)=2,86 (1,09-7,52)); the genotype 9.9 DAT VNTR 40bp (р=0,04; OR (95% CI)=1,4 (1,3-1,5)); on the contrary, (СС+СТ)-(ТТ)) variants of OPRK1-DRD2Ncol increased a chance to complete treatment program (р=0,004; OR (95% CI)=7.4 (1.8-30.4)), Kaplan-Meier survival analysis (р=0,016). The probability of completing treatment program by the carriers of these variants was higher in the oral naltrexone group (p=0.016), lower in the double placebo group (p=0.015), but did not influence on treatment outcomes in the naltrexone-implant group. Naltrexone-implant is a highly effective medication for treatment of opioid dependence and its effectiveness exceeds that of oral naltrexone and placebo. The study has shown the joint influence of opioid receptor genes and genes of dopaminergic system on treatment outcomes of opioid dependence. Genetic analysis is useful for determining potential responders to naltrexone treatment of opioid dependence.

Cravings as a mediator and moderator of drinking outcomes in the COMBINE study.

Investigators of the COMBINE (Combining Medications and Behavioral Interventions for Alcoholism) study examined whether combining medications with a behavioral intervention would improve outcomes over monotherapies. Unexpectedly, the combination did not offer any advantage over either treatment alone. This study aimed to explain the lack of incremental benefit offered by the combination over either monotherapy by assessing the role of cravings as a treatment mediator and moderator. Secondary mediation and moderation analyses of COMBINE study data. Eleven United States academic sites. A total of 863 patients randomized to one of four treatment groups: naltrexone (100 mg/day; n = 209), the combined behavioral intervention (CBI, n = 236), naltrexone and CBI combined (n = 213) and placebo naltrexone (n = 205). Percentage of days abstinent (PDA) measured between 13 and 16 weeks post-baseline. Cravings, the potential mediator/moderator, were measured at baseline, weeks 4 and 12 using the Obsessive-Compulsive Drinking Scale. Compared with placebo, naltrexone, CBI and the combination all increased PDA by an additional 6-10 percentage points for those with high cravings (P < 0.05 for all three treatment groups). None had significant effects on PDA for those with low cravings. The effects of all three treatments were mediated at least partially by cravings; craving reduction explained 48-53% of treatment effects (P < 0.05 for all three treatment groups). Furthermore, naltrexone appeared to reduce cravings at 4 weeks, while CBI did not reduce cravings until 12 weeks. The Combining Medications and Behavioral Interventions for Alcoholism (COMBINE) naltrexone + CBI combination may not be more beneficial than either monotherapy because craving reduction is a common mechanism of both.

Naltrexone with or without guanfacine for preventing relapse to opiate addiction in St.-Petersburg, Russia

BackgroundStress is a key precipitant to discontinuing naltrexone and relapsing to opiate abuse. Alpha-2 adrenergic agonists like guanfacine may reduce stress induced craving and have reduced opiate relapse in small clinical trials. MethodsThis randomized, double blind double dummy placebo-controlled 6-month trial tested oral naltrexone with or without guanfacine for reducing stress and preventing opiate relapse. We randomized 301 patients to: naltrexone 50mg/day+guanfacine 1mg/day (n=75) (N/G), naltrexone+guanfacine placebo (N/P) (n=76), naltrexone placebo+guanfacine (n=75) (P/G), and double placebo (n=75) (P/P). ResultsAmong the 75 patients in each group the percentage still retained on naltrexone treatment at six months was: N/G 26.7%, N/P 19.7% (p=0.258 to N/G), P/G 6.7% (p<0.05 to both N groups), and P/P 10.7% (p=0.013 to N+G). Guanfacine reduced the severity of stress particularly at weeks 10 and 18. Adverse events (AE) were infrequent (4.7%) without group differences, with most common AEs: headache, poor appetite, insomnia, and dizziness. ConclusionsAdding guanfacine to naltrexone did not improve treatment retention or opiate free urines, but it reduced both stress and craving at later time points in treatment, which may be related to stress-induced craving and the animal model of incubation of reinstatement. During treatment, HIV risk, anxiety, and depression reduced among all patients in treatment, regardless of group.

Modeling longitudinal drinking data in clinical trials: An application to the COMBINE study

BackgroundThere is a lack of consensus in the literature as to how to define drinking outcomes in clinical trials. Typically, separate statistical models are fit to assess treatment effects on several summary drinking measures. These summary measures do not capture the complexity of drinking behavior. We used the COMBINE study to illustrate a statistical approach for examining treatment effects on high-resolution drinking data. MethodsThis is a secondary data analysis of COMBINE participants randomly assigned to naltrexone, acamprosate, with medical management and/or combined behavioral intervention (CBI). Using a Poisson hurdle model, abstinence and number of drinks were simultaneously modeled as a function of treatment and covariates. An emphasis was placed on the evaluation of “risky drinking” (3 drinks/day for women and 4 for men). ResultsDuring treatment, naltrexone increased the odds of abstinence vs placebo naltrexone (OR=1.35 [1.06, 1.65]) but receiving CBI in addition to naltrexone (vs not) obscured this effect; thus, the naltrexone effect was largest in the group not receiving CBI (OR=1.87 [1.29, 2.46]). Naltrexone vs placebo naltrexone also reduced the risk of drinking in those who resumed risky drinking (RR=0.58 [0.24, 0.93]) and increased the odds of maintaining low risk drinking (OT=1.99 [1.07, 2.90]). Both effects were strongest in the absence of CBI when only “medical management” was provided. ConclusionsThe hurdle model is an appropriate statistical tool for assessing the effect of treatment on the two part drinking process, abstinence and number of drinks. When applied to COMBINE, results bolster the use of naltrexone in promoting abstinence and reduction in risky drinking.

The Combination Very Low-Dose Naltrexone–Clonidine in the Management of Opioid Withdrawal

Background: The management of withdrawal absorbs substantial clinical efforts in opioid dependence (OD). The real challenge lies in improving current pharmacotherapies. Although widely used, clonidine causes problematic adverse effects and does not alleviate important symptoms of opioid withdrawal, alone or in combination with the opioid antagonist naltrexone. Very low-dose naltrexone (VLNTX) has been shown to attenuate withdrawal intensity and noradrenaline release following opioid agonist taper, suggesting a combination with clonidine may result in improved safety and efficacy. Objectives: We investigated the effects of a VLNTX–clonidine combination in a secondary analysis of data from a double-blind, randomized opioid detoxification trial. Methods: Withdrawal symptoms and treatment completion were compared following VLNTX (.125 or .25 mg/day) and clonidine (.1–.2 mg q6h) in 127 individuals with OD undergoing 6-day methadone inpatient taper at a community program. Results: VLNTX was more effective than placebo or clonidine in reducing symptoms and signs of withdrawal. The use of VLNTX in combination with clonidine was associated with attenuated subjective withdrawal compared with each medication alone, favoring detoxification completion in comparison with clonidine or naltrexone placebo. VLNTX/clonidine was effective in reducing symptoms that are both undertreated and well controlled with clonidine treatment and was not associated with significant adverse events compared with other treatments. Conclusions and Scientific Significance: Preliminary results elucidate neurobiological mechanisms of OD and support the utility of controlled studies on a novel VLNTX + low-dose clonidine combination for the management of opioid withdrawal.Portions of this article were presented at the American Society of Addiction Medicine, 42nd Annual Medical Scientific Conference, April 14–17, 2011, in Washington, DC.

Opioid antagonism enhances marijuana's effects in heavy marijuana smokers

Studies in laboratory animals strongly suggest reciprocal modulation of the opioidergic and endocannabinoid systems, a relationship that has not been demonstrated in humans. This study sought to clarify this interaction by assessing how a range of naltrexone doses altered the subjective, cognitive, and cardiovascular effects of marijuana. Daily marijuana smokers (n = 29) participated in this within-subject, randomized, double-blind, placebo-controlled study. Naltrexone (0, 12, 25, 50, or 100 mg) was administered before active or inactive marijuana (3.27 or 0% THC) was smoked. Active marijuana increased subjective ratings of marijuana 'Strength,' 'High,' and positive subjective ratings of marijuana quality and drug effect including 'Liking,' 'Good,' and 'Take Again' compared to inactive marijuana. Naltrexone alone decreased ratings of 'Liking,' 'Take Again,' and 'Stimulated' compared with placebo, but increased ratings of drug 'Strength,' 'High,' 'Good,' 'Liking,' 'Stimulated,' and 'Take Again' when administered under active marijuana conditions. Active marijuana did not affect performance on cognitive tasks relative to inactive marijuana, whereas naltrexone decreased performance when administered alone or in combination with active marijuana. Active marijuana increased heart rate compared to inactive marijuana under placebo naltrexone conditions. Although naltrexone alone decreased heart rate, it further increased marijuana's cardiovascular effect. In heavy marijuana smokers opioid-receptor blockade enhanced the subjective and cardiovascular effects of marijuana, suggesting that endogenous opioids dampen cannabinoid effects in this population. These findings demonstrate that a broad range of clinically used doses of naltrexone potentially increases the abuse liability and cardiovascular risks of cannabinoids.

Naltrexone alone and with sertraline for the treatment of alcohol dependence in Alaska natives and non-natives residing in rural settings: a randomized controlled trial.

Access to specialty alcoholism treatment in rural environments is limited and new treatment approaches are needed. The objective was to evaluate the efficacy of naltrexone alone and in combination with sertraline among Alaska Natives and other Alaskans living in rural settings. An exploratory aim examined whether the Asn40Asp polymorphism of the mu-opioid receptor gene (OPRM1) predicted response to naltrexone, as had been reported in Caucasians. Randomized, controlled trial enrolling 101 Alaskans with alcohol dependence, including 68 American Indians/Alaska Natives. Participants received 16 weeks of either (1) placebo (placebo naltrexone + placebo sertraline), (2) naltrexone monotherapy (50 mg naltrexone + sertraline placebo) and (3) naltrexone + sertraline (100 mg) plus nine sessions of medical management and supportive advice. Primary outcomes included Time to First Heavy Drinking Day and Total Abstinence. Naltrexone monotherapy demonstrated significantly higher total abstinence (35%) compared with placebo (12%, p = 0027) and longer, but not statistically different, Time to First Heavy Drinking Day (p = 0.093). On secondary measures, naltrexone compared with placebo demonstrated significant improvements in percent days abstinent (p = 0.024) and drinking-related consequences (p = 0.02). Combined sertraline and naltrexone did not differ from naltrexone alone. The pattern of findings was generally similar for the American Indian/Alaska Native subsample. Naltrexone treatment response was significant within the group of 75 individuals who were homozygous for OPRM1 Asn40 allele. There was a small number of Asp40 carriers, precluding statistical testing of the effect of this allele on response. Naltrexone can be used effectively to treat alcoholism in remote and rural communities, with evidence of benefit for American Indians and Alaska Natives. New models of care incorporating pharmacotherapy could reduce important health disparities related to alcoholism.

Guanfacine Effective for Attention-Deficit/Hyerpactivity Disorder, but Side Effects Are Significant

Stress is a key precipitant to discontinuing naltrexone and relapsing to opiate abuse. Alpha-2 adrenergic agonists like guanfacine may reduce stress induced craving and have reduced opiate relapse in small clinical trials.This randomized, double blind double dummy placebo-controlled 6-month trial tested oral naltrexone with or without guanfacine for reducing stress and preventing opiate relapse. We randomized 301 patients to: naltrexone 50 mg/day + guanfacine 1 mg/day (n = 75) (N/G), naltrexone + guanfacine placebo (N/P) (n = 76), naltrexone placebo + guanfacine (n = 75) (P/G), and double placebo (n = 75) (P/P).Among the 75 patients in each group the percentage still retained on naltrexone treatment at six months was: N/G 26.7%, N/P 19.7% (p = 0.258 to N/G), P/G 6.7% (p < 0.05 to both N groups), and P/P 10.7% (p = 0.013 to N + G). Guanfacine reduced the severity of stress particularly at weeks 10 and 18. Adverse events (AE) were infrequent (4.7%) without group differences, with most common AEs: headache, poor appetite, insomnia, and dizziness.Adding guanfacine to naltrexone did not improve treatment retention or opiate free urines, but it reduced both stress and craving at later time points in treatment, which may be related to stress-induced craving and the animal model of incubation of reinstatement. During treatment, HIV risk, anxiety, and depression reduced among all patients in treatment, regardless of group.

Naltrexone with or without fluoxetine for preventing relapse to heroin addiction in St. Petersburg, Russia

This randomized placebo-controlled trial tested the efficacy of oral naltrexone with or without fluoxetine for preventing relapse to heroin addiction and for reducing HIV risk, psychiatric symptoms, and outcome. All patients received drug counseling with parental or significant-other involvement to encourage adherence. Patients totaling 414 were approached, 343 gave informed consent, and 280 were randomized (mean age, 23.6 ± 0.4 years). At 6 months, two to three times as many naltrexone patients as naltrexone placebo patients remained in treatment and had not relapsed, odds ratio (OR) = 3.5 (1.96–6.12), p < .0001. Overall, adding fluoxetine did not improve outcomes, OR = 1.35 (0.68–2.66), p = .49; however, women receiving naltrexone and fluoxetine showed a trend toward a statistically significant advantage when compared to women receiving naltrexone and fluoxetine placebo, OR = 2.4 (0.88–6.59), p = .08. HIV risk, psychiatric symptoms, and overall adjustment were markedly improved among all patients who remained on treatment and did not relapse, regardless of group assignment. More widespread use of naltrexone could be an important addition to addiction treatment and HIV prevention in Russia.

Naltrexone for heroin dependence treatment in St. Petersburg, Russia

Naltrexone may be more effective for treating opioid (heroin) dependence in Russia than in the U.S. because patients are mostly young and living with their parents, who can control medication compliance. In this pilot study we randomized 52 consenting patients who completed detoxification in St. Petersburg to a double blind, 6-month course of biweekly drug counseling and naltrexone, or counseling and placebo naltrexone. Significant differences in retention and relapse favoring naltrexone were seen beginning at 1 month and continuing throughout the study. At the end of 6 months, 12 of the 27 naltrexone patients (44.4%) remained in treatment and had not relapsed as compared to 4 of 25 placebo patients (16%; p<0.05). Since heroin dependence is the main way HIV is being spread in Russia, naltrexone is likely to improve treatment outcome and help reduce the spread of HIV if it can be made more widely available.

Effects of low-dose naltrexone on analgesia produced by hydrocodone

Purpose To assess the impact of oral naltrexone (NTX) on the analgesic effects of oral immediate-release hydrocodone (HYIR) in healthy subjects with thermally induced hyperalgesia. Methods Subjects first received a thermal discomfort test to determine hyperalgesic response and their responsiveness to opioid analgesic effects. Subjects who qualified then entered a 4-way crossover, double blind phase in which they received HYIR + NTX placebo, or HYIR + NTX 0.25, 0.5, or 1.0 mg. Results No significant differences occurred between HYIR + NTX placebo and HYIR + NTX 0.25, 0.5, or 1.0 mg in thermal discomfort scores, pain latency, or other measures of hyperalgesia. There were no significant differences among treatments or consistent dose-related trends in the subjective opioid agonist effects of HYIR measured in this study. No safety concerns were associated with any HYIR and/or NTX dose. No adverse events commonly associated with opioid use occurred with the NTX 1.0 mg dose. Conclusion No dose of NTX studied resulted in a significant decrease in HYIR-induced analgesia. There was no consistent, dose-related NTX effect on the subjective opioid agonist effects of HYIR measured in this study. Clinical Pharmacology & Therapeutics (2004) 75, P71–P71; doi: 10.1016/j.clpt.2003.11.267

Dose-response effects of low-dose naltrexone on the analgesia produced by hydrocodone

Purpose To determine the dose response of low-dose oral naltrexone (NTX) on the analgesia produced from 10 mg of hydrocodone (HYIR) in healthy subjects with thermally induced hyperalgesia. Methods Subjects first received a thermal discomfort test to determine hyperalgesic response and their responsiveness to opioid analgesic effects. Subjects who qualified entered a 5-treatment, 5-period crossover, double-blind phase in which they received placebo HYIR plus placebo NTX, HYIR plus placebo, or HYIR + 0.125, 0.250, or 0.500 mg of NTX. Results A suggested dose response was observed among the NTX doses on reducing thermal discomfort scores. Mean values among the different doses of NTX in thermal discomfort scores did not reveal any clinically relevant differences. Other measures of opioid effects such as 'drug liking' and 'feel the drug' revealed no differences among NTX doses. Observed adverse events were those commonly associated with opioids. Conclusion Increasing doses of naltrexone appear to slightly attenuate the analgesia from hydocodone; however, the effects do not appear to be relevant in this model. Clinical Pharmacology & Therapeutics (2004) 75, P71–P71; doi: 10.1016/j.clpt.2003.11.268

The Effect of Nimodipine on Opioid Antagonist-Induced Upregulation and Supersensitivity

Regulation of calcium flux has been suggested to play a role in acute and chronic effects of opioids. Previous studies have shown calcium channel blockers can inhibit opioid agonist-induced downregulation of μ-opioid receptors and may reduce the magnitude of tolerance. In the present study, we determined if calcium channel blockade would affect increases in opioid receptor density and functional supersensitivity produced by chronic opioid antagonist treatment in the mouse. Mice were implanted subcutaneously with a 15-mg naltrexone (NTX) or placebo pellet. Mice also were implanted with an osmotic minipump that infused nimodipine (100 μg/kg/day) or a second placebo pellet. This protocol yielded four groups: nimodipine–NTX; nimodipine–placebo; placebo–NTX; placebo–placebo. On the seventh day, pumps and pellets were removed. Twenty-four hours later, a morphine dose–response study was conducted (tail flick); or mice were sacrificed and saturation binding studies ([ 3H]DAMGO) were performed in whole brain. NTX treatment significantly increased the analgesic potency of morphine by ∼60%. Nimodipine increased the potency of morphine by ∼50%. For mice treated with both nimodipine and NTX, there was an additive effect on morphine potency (∼120% increase). In binding studies, NTX increased the density of μ-opioid receptors similarly (∼60–70%) in the presence and absence of nimodipine treatment, with no change in affinity. No effect of chronic nimodipine alone on μ-opioid receptor binding was observed. These data indicate that NTX-induced upregulation and supersensitivity are independent of calcium channel blockade by nimodipine. These results contrast with those from tolerance and downregulation studies, and confirm suggestions that different substrates mediate chronic opioid agonist and antagonist-induced effects in vivo. Finally, in a separate study, morphine potency was unaffected by acute nimodiopine (100 μg/kg; SC), suggesting that prolonged exposure to this calcium channel blocker is required to increase morphine potency.