Methadone, buprenorphine, and street drug interactions with antiretroviral medications

Effectiveness and Safety of Bictegravir/Emtricitabine/Tenofovir Alafenamide in Patients With HIV-1 Infection and Ongoing Substance Use Disorder: The BASE Study

Background

People with human immunodeficiency virus (HIV) and substance use disorder (PWH/SUD) are at higher risk of nonadherence to antiretroviral therapy. Bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF) exhibits high rates of efficacy with a favorable adverse event profile. The BASE study (NCT03998176) is a phase 4, single-arm study evaluating the effectiveness and safety of B/F/TAF among PWH/SUD.

Methods

Viremic (HIV RNA >1000 copies/mL) PWH/SUD initiated B/F/TAF once daily for 48 weeks (W). The primary endpoint was proportion of participants with HIV RNA <50 copies/mL at W24. Secondary endpoints were proportion of participants with HIV-1 RNA <50 copies/mL at W48, safety, B/F/TAF adherence (dried blood spot [DBS] concentrations of emtricitabine triphosphate and tenofovir diphosphate [TFV-DP]), substance use (NIDA-ASSIST), and quality of life (SF-12).

Results

Forty-three participants were enrolled; 95% reported methamphetamine use. Median age was 38 (range, 21-62) years; 21% were female, 81% White, 14% Black, and 16% Hispanic. Thirty-two (74%) and 21 (49%) participants had HIV RNA <50 copies/mL (intention-to-treat) at W24 and W48, respectively. Seven participants (16%) experienced confirmed virologic failure through W48; 1 developed emergent drug resistance (M184V). Fifteen participants (35%) experienced grade ≥3 adverse events. Five participants (12%) reported suicidal ideation; none resulted in discontinuation. Median DBS concentrations were representative of 5-6 doses/week (TFV-DP, 1603 fmol/punches). NIDA-ASSIST scores declined from baseline to W48 with methamphetamine use decreasing most (-7.9 points; -29%), and SF-12 physical/mental scores increased 1.2 and 7.6 points, respectively.

Conclusions

B/F/TAF among a high-risk population of PWH/SUD resulted in an initial 72% viral suppression rate at W24 before dropping to 49% at W48 as retention declined. One participant developed emergent drug resistance (M184V).

Drugs of Abuse and Their Impact on Viral Pathogenesis

Commonly misused substances such as alcohol, cocaine, heroin, methamphetamine, and opioids suppress immune responses and may impact viral pathogenesis. In recent years, illicit use of opioids has fueled outbreaks of several viral pathogens, including the human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV). This review focuses on the myriad of mechanisms by which drugs of abuse impact viral replication and disease progression. Virus–drug interactions can accelerate viral disease progression and lead to increased risk of virus transmission.

Effect of HIV, antiretrovirals, and genetics on methadone pharmacokinetics: Results from the methadone antiretroviral pharmacokinetics study

BACKGROUND

Methadone treatment of opioid use disorder in HIV-infected individuals is complicated by drug-drug interactions. Genetic and other cofactors further contribute to interindividual variability in methadone pharmacokinetics. We used population pharmacokinetics to estimate the effect of drug-drug interactions, genetics, and other cofactors on methadone pharmacokinetics in a methadone maintained population in Vietnam.

METHODS

Plasma R- and S-methadone levels were measured in 309 methadone maintained individuals just before and 2-5 h following methadone dosing. A linear one-compartment population pharmacokinetic model with first-order conditional estimation with interaction was used to evaluate methadone clearance (CL/F) and volume of distribution (V/F). The influence of covariates on parameter estimates was evaluated using stepwise covariate modeling. Covariates included HIV status, antiretroviral use (efavirenz or nevirapine), weight, BMI, age, methadone dose, and 8 single nucleotide polymorphisms in across the CYP2B6, ABCB1, and NR1I3 genes.

RESULTS

Taking either efavirenz or nevirapine increased R-methadone CL/F 220%. Nevirapine and efavirenz increased S-methadone CL/F by 404% and 273%, respectively. Variants in NR1I3 increased R- and S-methadone CL/F by approximately 20% only in patients taking efavirenz. Different alleles in ABCB1 rs2032582 either increased or decreased R-methadone CL/F by 10%. The CYP 2B6*4 variant decreased S-methadone CL/F by 18%. HIV-infection increased R- and S-methadone CL/F and V/F by 24%-39%.

CONCLUSIONS

The HIV antiretrovirals nevirapine and efavirenz significantly increase methadone clearance. Variants inNR1I3 increased the effect of efavirenz on methadone clearance. Other variants affecting methadone CL/F were also confirmed. To our knowledge, this is the first report of HIV itself affecting methadone pharmacokinetics.

Factors Affecting Changes of Cluster of Differentiation 4 Cell Counts Among Human Immunodeficiency Virus-positive People Who Inject Heroin and Receive Methadone Maintenance Treatment

AIMS

Opioids have been hypothesized to suppress the immune function and worsen outcomes among people living with human immunodeficiency virus (HIV). The study aimed to identify key factors associated with the increased cluster of differentiation 4 (CD4) cell counts among HIV-positive people who inject heroin and receive methadone maintenance treatment (MMT).

METHODS

This longitudinal study was conducted at a psychiatric hospital in Northern Taiwan. Participants were recruited from 2006 through 2011, and received CD4 cell counts and HIV viral load monitoring once every 4 to 6 months. Trend in CD4 cell counts, defined as change in CD4 cell count over time, was used as the outcome measure. Independent variables included MMT-related factors and baseline characteristics. Baseline characteristics included age, gender, CD4 cell count, HIV viral load, tests for other infections, liver function tests, and urine drug screens.

RESULTS

Three hundred and fifty one participants were recruited during the study period. The multivariate linear mixed model analysis revealed a higher MMT attendance rate, a higher baseline CD4 cell count, and a shorter duration of MMT were associated with an increase in CD4 cell count over time.

CONCLUSIONS

The study showed better adherence to MMT was associated with better preserved immune functions. The negative impact of duration of MMT on CD4 cell counts may be ameliorated by improving the attendance rate, initiation of MMT earlier when the baseline CD4 cell count is still relatively high and by the other beneficial effects of MMT, such as healthier lifestyles with reduced use of short-acting opioids.

Treating viruses in the brain: Perspectives from NeuroAIDS

Aggressive use of antiretroviral therapy has led to excellent viral suppression within the systemic circulation. However, despite these advances, HIV reservoirs still persist. The persistence of HIV within the brain can lead to the development of HIV-associated neurocognitive disorders (HAND). Although the causes of the development of neurocognitive disorders is likely multifactorial, the inability of antiretroviral therapy to achieve adequate concentrations within the brain is likely a major contributing factor. Information about antiretroviral drug exposure within the brain is limited. Clinically, drug concentrations within the cerebrospinal fluid (CSF) are used as markers for central nervous system (CNS) drug exposure. However, significant differences exist; CSF concentration is often a poor predictor of drug exposure within the brain. This article reviews the current information regarding antiretroviral exposure within the brain in humans as well as preclinical animals and discusses the impact of co-morbidities on antiretroviral efficacy within the brain. A more thorough understanding of antiretroviral penetration into the brain is an essential component to the development of better therapeutic strategies for neuroAIDS.

The impact of high-dose opioid prescription on mortality rates among people living with HIV: A retrospective cohort study

OBJECTIVES

High-dose opioid use is associated with increased morbidity, mortality, and healthcare utilization. People living with HIV (PLHIV) are frequently prescribed these medications to manage their pain. However, little is known about the relationship between being prescribed high doses of opioids (> 90 MME/d) and mortality risk among this population. The objective of this study was to examine the trends in mortality and the relationship between high-dose opioid analgesic prescribing and mortality among PLHIV.

METHODS

Utilizing the STOP HIV/AIDS cohort--a population-level linked database of treatment of PLHIV in British Columbia--we conducted bivariable and multivariable generalized estimating equation (GEE) models with a Poisson distribution to examine the relationship between high-dose opioid prescription and all-cause mortality rates in the study sample.

RESULTS

Between 1996 and 2015, 9272 PLHIV were included in the study. Age- and sex-adjusted mortality rate (using the 2011 Canadian population as the reference) was 30.99 per 1000 person-years (95% confidence interval [CI]: 28.11-33.88). In a multivariable GEE model with adjustment for various demographic and clinical confounders, there was a positive and independent association between being prescribed high-dose opioids and all-cause mortality rates (adjusted rate ratio [ARR] = 3.01; 95%CI: 2.47-3.66).

DISCUSSION

We found that mortality rates were significantly higher among PLHIV who were prescribed high-dose opioids compared to those who were prescribed lower doses. Our results highlight the risk associated with the prescribing of high-dose opioids to manage HIV-related pain and emphasize the need to explore non-opioid approaches to pain management.

Use of generally recognized as safe or dietary compounds to inhibit buprenorphine metabolism: potential to improve buprenorphine oral bioavailability

The present study evaluated the potential of five generally recognized as safe (GRAS) or dietary compounds (α-mangostin, chrysin, ginger extract, pterostilbene and silybin) to inhibit oxidative (CYP) and conjugative (UGT) metabolism using pooled human intestinal and liver microsomes. Buprenorphine was chosen as the model substrate as it is extensively metabolized by CYPs to norbuprenorphine and by UGTs to buprenorphine glucuronide. Chrysin, ginger extract, α-mangostin, pterostilbene and silybin were tested for their inhibition of the formation of norbuprenorphine or buprenorphine glucuronide in both intestinal and liver microsomes. Pterostilbene was the most potent inhibitor of norbuprenorphine formation in both intestinal and liver microsomes, with IC50 values of 1.3 and 0.8 μM, respectively, while α-mangostin and silybin most potently inhibited buprenorphine glucuronide formation. The equipotent combination of pterostilbene and ginger extract additively inhibited both pathways in intestinal microsomes. Since pterostilbene and ginger extract showed potent CYP and/or UGT inhibition of buprenorphine metabolism, their equipotent combination was tested to assess the presence of synergistic inhibition. However, because the combination showed additive inhibition, it was not used while performing IVIVE analysis. Based on quantitative in vitro-in vivo extrapolation, pterostilbene (21 mg oral dose) appeared to be most effective in improving the mean predicted Foral and AUC∞ PO of buprenorphine from 3 ± 2% and 340 ± 330 ng*min/ml to 75 ± 8% and 36,000 ± 25,000 ng*min/ml, respectively. At a 10-fold lower dose of pterostilbene, the predicted buprenorphine Foral approximated sublingual bioavailability (~35%) and showed a 2-4 fold reduction in the variability around the predicted AUC∞ PO of buprenorphine. These results demonstrate the feasibility of using various GRAS/dietary compounds to inhibit substantially the metabolism by CYP and UGT enzymes to achieve higher and less variable oral bioavailability. This inhibitor strategy may be useful for drugs suffering from low and variable oral bioavailability due to extensive presystemic oxidative and/or conjugative metabolism.

Histopathological study of liver tissue due to methadone consumption and its effect on liver enzymes and inflammatory indices in rat

Background

Methadone (MET)-based treatment is currently one of the best known approaches in the treatment of opioid dependence. It is claimed that MET use exerts adverse effects on the performance of some organs, especially liver. Thus, the present study aims to investigate MET effects on the hepatic tissue as well as its effect on the hepatic enzyme levels and inflammatory markers in rats.

Materials and methods

Twenty-eight mature male Wistar rats underwent an 8-week treatment in four equal groups including the control group (an ordinary daily dietary regime) as well as the experimental groups 1, 2, and 3 (an ordinary daily dietary regime and gavage-fed on MET syrup for 5, 20, and 40 mg/kg body weight per day). Blood samples were collected from all rats in the beginning and end of the study to measure their hepatic enzyme levels and inflammatory markers. In the end, their livers were subjected to histological examinations.

Results

The mean serum levels of hepatic enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) increased considerably across all the three groups that had received various dosages of MET (5, 20, and 40 mg/kg) in the end of the study as compared to the beginning of the study (P<0.001). It was also found that the inflammatory indicators (interleukin-6, tumor necrosis factor-alpha, and C-reactive protein) rose significantly in the groups that had received various dosages of MET in contrast to the control group (P<0.01, P<0.001, and P<0.001, respectively). The histopathological images of the liver cross-sections revealed dosage-dependent tissue changes in the groups that had received various dosages of MET.

Conclusion

The present study tried to prove the adverse effects of MET in the development of liver damage. Since MET-based treatment is frequently prescribed by physicians for curing the addiction to narcotics, better strategies are required for its correct usage.

Treatment of opioid dependence with buprenorphine: current update

Opioid maintenance treatment is the first-line approach in opioid dependence. Both the full opioid agonist methadone (MET) and the partial agonist buprenorphine (BUP) are licensed for the treatment of opioid dependence. BUP differs significantly from MET in its pharmacology, side effects, and safety issues. For example, the risk of respiratory depression is lower than with MET. The risk of diversion and injection of BUP have been reduced by also making it available as a tablet containing the opioid antagonist naloxone. This review summarizes the clinical effects of BUP and examines possible factors that can support decisions regarding the use of BUP or MET in opioid-dependent people.

Pharmacokinetic Considerations for Combining Antiretroviral Therapy, Direct-Acting Antiviral Agents for Hepatitis C Virus, and Addiction Treatment Medications

There are many factors that can affect the pharmacokinetics (PK) of drugs. Pathophysiological changes from disease states can alter the mechanisms that control the PK of antiretrovirals (ARVs), direct-acting antivirals (DAAs), and addiction treatment medications. Drug-drug interaction pathways of certain ARVs and DAAs can be very complex, with agents being substrates, inhibitors, or inducers of multiple metabolic and transporter pathways. Buprenorphine and methadone may be used in HIV- and hepatitis C virus (HCV)-infected patients and may also be affected by drug interactions. Current research is focused on novel PK analyses, which aim to describe the PK of agents within organs that host the infection of interest, such as within hepatocytes during treatment for HCV. Modeling techniques allow for the prediction of drug PK in specific organs and the plasma compartment. This review will provide a summary of these areas while exploring PK considerations for ARVs, DAAs, and addiction treatment medications.

Factors associated with concurrent heroin use among patients on methadone maintenance treatment in Vietnam: A 24-month retrospective analysis of a nationally representative sample

BACKGROUND

Methadone maintenance treatment (MMT) is highly effective for reducing heroin use and HIV transmission among people who inject opioids. We sought to measure and understand factors associated with continued heroin use, a critical factor affecting treatment outcome among MMT patients in Vietnam.

METHOD

We collected data from medical charts of a nationally representative sample of patients who were on MMT from May 2008 to December 2013. We selected 10 MMT clinics using probability proportional to size and 50 patients/clinic by systematic random sampling. Concurrent heroin use was defined by self-report/positive urine test recorded in patient charts during month 3, 6, 12, and 24 after MMT initiation. We used multivariable logistic regression to identify factors associated with concurrent heroin use over the first 24 months in treatment.

FINDINGS

All clients used heroin at baseline; concurrent heroin use was 55% at month 3; 19%, 14.6% and 15.2% at month 6, 12, and 24, respectively. Having no family emotional/financial support at baseline versus having this support (AOR = 2.03; 95% confidence interval [CI] = 1.17-3.53); using heroin for <15 years versus ≥15 years at baseline (AOR = 1.55; 95% CI = 1.01-2.38); being HIV-infected/not on antiretroviral treatment (ART; AOR = 1.79; 95% CI = 1.07-2.98) or being HIV infected/on ART (AOR = 2.39; 95% CI = 1.61-3.55), versus not being HIV infected; baseline methamphetamine use versus non-use (AOR = 2.68; 95% CI = 1.08-6.65), were associated with increased odds of concurrent heroin use among patients.

CONCLUSION

The association between concurrent heroin use among MMT patients and lack of family emotional/financial support, highlights the critical importance of these types of support for successful treatment. Association with shorter heroin use history suggests motivational enhancement may reduce concurrent heroin use. Living with HIV, whether on ART or not, is associated with increased concurrent heroin use and suggests safe injection commodities and education, and drug-drug interaction management, are needed for this subgroup. Though few MMT clients reported baseline methamphetamine use, its association with later heroin use suggests the need for effective methamphetamine use interventions.

Methadone Pharmacogenetics: CYP2B6 Polymorphisms Determine Plasma Concentrations, Clearance, and Metabolism

BACKGROUND

Interindividual variability in methadone disposition remains unexplained, and methadone accidental overdose in pain therapy is a significant public health problem. Cytochrome P4502B6 (CYP2B6) is the principle determinant of clinical methadone elimination. The CYP2B6 gene is highly polymorphic, with several variant alleles. CYP2B6.6, the protein encoded by the CYP2B6*6 polymorphism, deficiently catalyzes methadone metabolism in vitro. This investigation determined the influence of CYP2B6*6, and other allelic variants encountered, on methadone concentrations, clearance, and metabolism.

METHODS

Healthy volunteers in genotype cohorts CYP2B6*1/*1 (n = 21), CYP2B6*1/*6 (n = 20), and CYP2B6*6/*6 (n = 17), and also CYP2B6*1/*4 (n = 1), CYP2B6*4/*6 (n = 3), and CYP2B6*5/*5 (n = 2) subjects, received single doses of IV and oral methadone. Plasma and urine methadone and metabolite concentrations were determined by tandem mass spectrometry.

RESULTS

Average S-methadone apparent oral clearance was 35 and 45% lower in CYP2B6*1/*6 and CYP2B6*6/*6 genotypes, respectively, compared with CYP2B6*1/*1. R-methadone apparent oral clearance was 25 and 35% lower in CYP2B6*1/*6 and CYP2B6*6/*6 genotypes, respectively, compared with CYP2B6*1/*1. R- and S-methadone apparent oral clearance was threefold and fourfold greater in CYP2B6*4 carriers. IV and oral R- and S-methadone metabolism was significantly lower in CYP2B6*6 carriers compared with that of CYP2B6*1 homozygotes and greater in CYP2B6*4 carriers. Methadone metabolism and clearance were lower in African Americans in part because of the CYP2B6*6 genetic polymorphism.

CONCLUSIONS

CYP2B6 polymorphisms influence methadone plasma concentrations, because of altered methadone metabolism and thus clearance. Genetic influence is greater for oral than IV methadone and S- than R-methadone. CYP2B6 pharmacogenetics explains, in part, interindividual variability in methadone elimination. CYP2B6 genetic effects on methadone metabolism and clearance may identify subjects at risk for methadone toxicity and drug interactions.

Impact of a methadone maintenance therapy pilot in Vietnam and its role in a scaled-up response

BACKGROUND

As a dual response to the HIV epidemic and the high level of injecting drug use in Vietnam, the Ministry of Health (MOH) initiated a pilot methadone maintenance therapy (MMT) program in Hai Phong and Ho Chi Minh City (HCMC) in early 2009. The objectives of the pilot were to provide evidence on whether MMT could be successfully implemented in Vietnam and scaled up to other localities.

METHODS

A prospective study was conducted among 965 opiate drug users admitted to the pilot. Data on demographic characteristics, sexual behaviors, substance use behaviors (including heroin use), and blood-borne virus infection (HIV, hepatitis B, and hepatitis C) were collected at treatment initiation and then again at 3-, 6-, 9-, 12-, 18-, and 24-month intervals thereafter.

RESULTS

Twenty-four months after treatment initiation, heroin use as measured by urine test or self-report had reduced from 100 % of participants at both sites to 14.6 % in Hai Phong and 22.9 % in HCMC. When adjusted for multiple factors in Generalized Estimating Equations (GEE) logistic regression modeling, independent predictors of continued heroin use after 24 months of MMT in HCMC were the following: poor methadone adherence (adjusted odds ratio (AOR) = 3.7, 95 % confidence interval (CI) 1.8-7.8); currently on antiretroviral treatment (ART) (AOR = 1.8, 95 % CI 1.4-2.4); currently on TB treatment (AOR = 2.2, 95 % CI 1.4-3.4); currently experiencing family conflict (AOR = 1.6, 95 % CI 1.1-2.4); and currently employed (AOR = 0.8, 95 % CI 0.6-1.0). For Hai Phong participants, predictors were the following: currently on ART (AOR = 2.0, 95 % CI = 1.4-3.0); currently experiencing family conflict (AOR = 2.0, 95 % CI = 1.0-3.9); and moderate adherence to methadone (AOR = 2.1, 95 % CI = 1.2-1.9). In Hai Phong, the percentage of participants who were employed had also increased by end of study from 35.0 to 52.8 %, while in HCMC the level remained relatively unchanged, between 52.2 and 55.1 %.

DISCUSSION

Study findings were used in multiple fora to convince policymakers and the public on the significant and vital role MMT can play in reducing heroin use and improving quality of life for individuals and families. Four years after this study was completed, Vietnam had expanded MMT to 162 clinics in 44 provinces serving 32,000 patients.

A Review of the Toxicity of HIV Medications II: Interactions with Drugs and Complementary and Alternative Medicine Products

For many patients today, HIV has become a chronic disease. For those patients who have access to and adhere to lifelong antiretroviral (ARV) therapy, the potential for drug-drug interactions has become a real and life-threatening concern. It is known that most ARV drug interactions occur through the cytochrome P450 (CYP) pathway. Medications for comorbid medical conditions, holistic supplements, and illicit drugs can be affected by CYP inhibitors and inducers and have the potential to cause harm and toxicity. Protease inhibitors (PIs) tend to inhibit CYP3A4, while most non-nucleoside reverse transcriptase inhibitors (NNRTIs) tend to induce the enzyme. As such, failure to adjust the dose of co-administered medications, such as statins and steroids, may lead to serious complications including rhabdomyolysis and hypercortisolism, respectively. Similarly, gastric acid blockers can decrease several ARV absorption, and warfarin doses may need to be adjusted to maintain therapeutic concentrations. Illicit drugs such as methylenedioxymethamphetamine (MDMA, "ecstasy") in combination with PIs lead to increased toxicity, while the concomitant administration of sedative drugs such as midazolam and alprazolam in patients taking PIs can result in prolonged sedation, delayed recovery, and increased length of stay. Even supplements like St. John's Wort can alter PI concentrations. In theory, any drug that is metabolized by CYP has potential for a pharmacokinetic drug-drug interaction with all PIs, cobicistat, and most NNRTIs. When adding a new medication to an ARV regimen, use of a drug-drug interaction software and/or consultation with a clinical pharmacist/pharmacologist or HIV specialist is recommended.

Arrhythmia associated with buprenorphine and methadone reported to the Food and Drug Administration

AIM

To assess the relative frequency of reporting of adverse events involving ventricular arrhythmia, cardiac arrest, corrected QT interval (QTc) prolongation or torsade de pointes to the US Food and Drug Administration (FDA) between buprenorphine and methadone.

DESIGN

Retrospective pharmacoepidemiological study.

SETTING

Adverse drug events reported spontaneously to the FDA between 1969 and June 2011 originating in 196 countries (71% events from the United States).

CASES

Adverse event cases mentioning methadone (n = 14 915) or buprenorphine (n = 7283) were evaluated against all other adverse event cases (n = 4 796 017).

MEASUREMENTS

The primary outcome was the composite of ventricular arrhythmia or cardiac arrest. The secondary outcome was the composite of QTc prolongation or torsade de pointes. The proportional reporting ratio (PRR) was used to identify disproportionate reporting defined as a PRR > 2, χ(2) error > 4, with ≥ 3 cases.

FINDINGS

There were 132 (1.8%) ventricular arrhythmia/cardiac arrest and 19 (0.3%) QTc prolongation/torsade de pointes cases associated with buprenorphine compared with 1729 (11.6%) ventricular arrhythmia/cardiac arrest and 390 (2.6%) QTc prolongation/torsade de pointes cases involving methadone. PRRs associated with buprenorphine were not significant for ventricular arrhythmia/cardiac arrest (1.10, 95%, confidence interval (0.93-1.31, χ(2)  = 1.2) or QTc prolongation/torsade de pointes (1.03, 95% CI = 0.66-1.62, χ(2)  = 0.01), but were for methadone (7.20, 95% CI = 6.88-7.52, χ(2)  = 8027; 10.7, 95% CI = 9.66-11.8, χ(2)  = 1538, respectively).

CONCLUSION

In spontaneously reported adverse events, methadone is associated with disproportionate reporting of cardiac arrhythmias, whereas buprenorphine is not. Although these findings probably reflect clinically relevant differences, a causal connection cannot be presumed and disproportionality analysis cannot quantify absolute risk per treatment episode. Population-based studies to definitively quantify differential incidence rates are warranted.

Long-term Prescription of Opioids and/or Benzodiazepines and Mortality Among HIV-Infected and Uninfected Patients

BACKGROUND

Increased long-term prescription of opioids and/or benzodiazepines necessitates evaluating risks associated with their receipt. We sought to evaluate the association between long-term opioids and/or benzodiazepines and mortality in HIV-infected patients receiving antiretroviral therapy and uninfected patients.

METHODS

Prospective analysis of all-cause mortality using multivariable methods and propensity score matching among HIV-infected patients receiving antiretroviral therapy and uninfected patients.

RESULTS

Of 64,602 available patients (16,989 HIV-infected and 47,613 uninfected), 27,128 (exposed and unexposed to long-term opioids and/or benzodiazepines) were 1:1 matched by propensity score. The hazard ratio for death was 1.40 [95% confidence interval (CI): 1.22 to 1.61] for long-term opioid receipt, 1.26 (95% CI: 1.08 to 1.48) for long-term benzodiazepine receipt, and 1.56 (95% CI: 1.26 to 1.92) for long-term opioid and benzodiazepine receipt. There was an interaction (P = 0.01) between long-term opioid receipt and HIV status with mortality. For long-term opioid receipt, the hazard ratio was 1.46 (95% CI: 1.15 to 1.87) among HIV-infected patients, and 1.25 (95% CI: 1.05 to 1.49) among uninfected patients. Mortality risk was increased for patients receiving both long-term opioids and benzodiazepines when opioid doses were ≥ 20 mg morphine-equivalent daily dose and for patients receiving long-term opioids alone when doses were ≥ 50 mg morphine-equivalent daily dose.

CONCLUSIONS

Long-term opioid receipt was associated with an increased risk of death; especially with long-term benzodiazepine receipt, higher opioid doses, and among HIV-infected patients. Long-term benzodiazepine receipt was associated with an increased risk of death regardless of opioid receipt. Strategies to mitigate risks associated with these medications, and caution when they are coprescribed, are needed particularly in HIV-infected populations.

HIV-gp120 and physical dependence to buprenorphine

BACKGROUND

Opioids are among the most effective and commonly used analgesics in clinical practice for severe pain. However, the use of opioid medications is clinically limited by several adverse properties including dependence. While opioid dependence is a complex health condition, the treatment of HIV-infected individuals with opioid dependence presents additional challenges. The goal of this study was to examine the physical dependence to buprenorphine in the context of HIV.

METHODS

Young adult male rats (Sprague-Dawley) were pretreated with HIV-1 envelope glycoprotein 120 (gp120) injected into the periaqueductal gray area (PAG) and we examined the impact on physical dependence to opioid.

RESULTS

It was found that the physical dependence to methadone occurred earlier than that to buprenorphine, and that gp120 did not enhance or precipitate the buprenorphine withdrawal.

CONCLUSION

The results suggest that buprenorphine could be the better therapeutic option to manage opioid dependence in HIV.

Drug-Drug Interactions With Antiviral Agents in People Who Inject Drugs Requiring Substitution Therapy

OBJECTIVE

To describe potential drug-drug interactions in the area of HIV/hepatitis C virus (HCV) coinfection and injection drug use, including those between antiretrovirals (ARVs), direct-acting antivirals (DAAs), and opioid-agonist therapy, and to supply a practical approach to their management.

DATA SOURCES

We searched PubMed for relevant articles published up until February 2015 as well as conference reports and drug-drug-interaction Web sites.

DATA SELECTION AND DATA EXTRACTION

We used the following search terms: pharmacokinetic and pharmacodynamic drug-drug interaction, opioid substitution, HIV, hepatitis and the individual names of the relevant agents of the following drug classes and the drug classes itself: reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors, protease inhibitors, direct-acting antivirals, opioide, benzodiazepines, anticonvulsants, antidepressants and antipsychotics. Additional references were identified from a review of literature citations and drug-drug interaction Web sites. In our evaluation, we included German- and English-language studies and reports addressing drug-drug interactions between opioid agonist therapy and ARVs or DAAs.

DATA SYNTHESIS

Pharmacokinetic data were available for all ARVs and DAAs except rilpivirine, indinavir, saquinavir, maraviroc, dolutegravir, and MK-8742 with buprenorphine as well as maraviroc with methadone Drug-drug interactions of potential clinical relevance are most likely to occur between opioid-replacement therapy and ARVs, particularly the nonnucleoside reverse transcriptase inhibitors, efavirenz and nevirapine, and HIV protease inhibitors.

CONCLUSION

Integrase inhibitors may be safely coadministered with opioid-replacement therapy. With respect to HCV DAAs, most currently approved and late-stage investigational agents do not have clinically significant interactions with opioid-replacement therapy. ARV and DAAs may interact with other drug classes commonly used in the opioid-dependent population, including benzodiazepines, antidepressants, anticonvulsants, and antipsychotics.

Within-prison drug injection among HIV-infected male prisoners in Indonesia: a highly constrained choice

BACKGROUND

In Indonesia, incarceration of people who inject drugs (PWID) and access to drugs in prison potentiate within-prison drug injection (WP-DI), a preventable and extremely high-risk behavior that may contribute substantially to HIV transmission in prison and communities to which prisoners are released.

AIMS

This mixed method study examined the prevalence, correlates, and social context of WP-DI among HIV-infected male prisoners in Indonesia.

METHODS

102 randomly selected HIV-infected male prisoners completed semi-structured voice-recorded interviews about drug use changes after arrest, drug use cues within prison, and impact of WP-DI on HIV and addiction treatment. Logistic regression identified multivariate correlates of WP-DI and thematic analysis of interview transcripts used grounded-theory.

RESULTS

Over half (56%) of participants reported previous WP-DI. Of those, 93% shared injection equipment in prison, and 78.6% estimated sharing needles with ≥ 10 other prisoners. Multivariate analyses independently correlated WP-DI with being incarcerated for drug offenses (AOR = 3.29, 95%CI = 1.30-8.31, p = 0.011) and daily drug injection before arrest (AOR = 5.23, 95%CI = 1.42-19.25, p = 0.013). Drug availability and proximity to drug users while incarcerated were associated with frequent drug craving and escalating drug use risk behaviors after arrest. Energetic heroin marketing and stigmatizing attitudes toward methadone contribute to WP-DI and impede addiction and HIV treatment.

CONCLUSIONS

Frequent WP-DI and needle sharing among these HIV-infected Indonesian prison inmates indicate the need for structural interventions that reduce overcrowding, drug supply, and needle sharing, and improve detection and treatment of substance use disorders upon incarceration to minimize WP-DI and associated harm.

Influence of HIV antiretrovirals on methadone N-demethylation and transport

Drug interactions involving methadone and/or HIV antiretrovirals can be problematic. Mechanisms whereby antiretrovirals induce clinical methadone clearance are poorly understood. Methadone is N-demethylated to 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) by CYP2B6 and CYP3A4 in vitro, but by CYP2B6 in vivo. This investigation evaluated human hepatocytes as a model for methadone induction, and tested the hypothesis that methadone and EDDP are substrates for human drug transporters. Human hepatocyte induction by several antiretrovirals of methadone N-demethylation, and CYP2B6 and CYP3A4 transcription, protein expression and catalytic activity, and pregnane X receptor (PXR) activation were evaluated. Methadone and EDDP uptake and efflux by overexpressed transporters were also determined. Methadone N-demethylation was generally not significantly increased by the antiretrovirals. CYP2B6 mRNA and activity (bupropion N-demethylation) were induced by several antiretrovirals, as were CYP3A4 mRNA and protein expression, but only indinavir increased CYP3A activity (alfentanil dealkylation). CYP upregulation appeared related to PXR activation. Methadone was not a substrate for uptake (OCT1, OCT2, OCT3, OATP1A2, OATP1B1, OATP1B3, OATP2B1) or efflux (P-gp, BCRP) transporters. EDDP was a good substrate for P-gp, BCRP, OCT1, OCT3, OATP1A2, and OATP1B1. OATP1A2- and OCT3-mediated EDDP uptake, and BCRP-mediated EDDP efflux transport, was inhibited by several antiretrovirals. Results show that hepatocyte methadone N-demethylation resembles expressed and liver microsomal metabolism more than clinical metabolism. Compared with clinical studies, hepatocytes underreport induction of methadone metabolism by HIV drugs. Hepatocytes are not a good predictive model for clinical antiretroviral induction of methadone metabolism and not a substitute for clinical studies. EDDP is a transporter substrate, and is susceptible to transporter-mediated interactions.

New developments in the management of opioid dependence: focus on sublingual buprenorphine-naloxone

Opioid maintenance therapy is a well-established first-line treatment approach in opioid dependence. Buprenorphine, a partial opioid agonist, has been found by numerous studies to be an effective and safe medication in the treatment of opioid dependence. At present, buprenorphine is available as a monodrug or in a fixed 4:1 ratio combination with naloxone. A diminished risk of diversion and abuse for the buprenorphine-naloxone combination is likely but not firmly established. Conventional formulations are given sublingually to avoid the hepatic first-pass effect. A novel film tablet is available only in the US and Australia. Other novel, sustained-release formulations (implant, depot) are currently being developed and tested. Recent studies, including a Cochrane meta-analysis, suggest that the retention with buprenorphine is lower than for methadone, but that buprenorphine may be associated with less drug use. Higher doses of buprenorphine are associated with better retention rates. Buprenorphine has a ceiling effect at the opioid receptor with regard to respiratory depression, and may cause fewer fatal intoxications than methadone. Possible antidepressant effects of buprenorphine and its use in comorbid psychiatric patients has not been studied in much detail. Clinical implications are discussed.

Associated factors of drug-drug interactions of highly active antiretroviral therapy: report from a referral center

OBJECTIVE

To assess different aspects of potential drug-drug interactions (DDIs) including incidence, severity, level of evidence and probable associated factors in Iranian HIV-infected individuals receiving antiretroviral therapy.

METHODS

All adult HIV-infected patients under highly active antiretroviral therapy regimen attending a referral HIV clinic during 1 year were screened retrospectively for potential moderate or severe DDIs by the Lexi-Interact On-Desktop software.

RESULTS

Near seventy percent (69.89%) of detected DDIs in our population were major. The three most common detected potential DDIs were efavirenz + methadone (11 cases), lopinavir-ritonavir + sulfamethoxazole-trimethoprim, (10 cases) and lamivudine + ribavirin (7 cases). Lopinavir-ritonavir (27.96%) and citalopram (23.66%) were the most common offending antiretroviral and non-antiretroviral agents, respectively.

CONCLUSION

Performing multicenter and prospective studies is warranted to assess the real clinical as well as economic impacts of DDIs on HIV-infected patients receiving antiretroviral agents in our population and also to develop efficient preventive strategies.

Considerations on the role of buprenorphine in recovery from heroin addiction from a UK perspective

The United Kingdom Drug Strategy emphasises recovery as a key focus in the treatment of drug dependence. A framework for recovery is defined in the Recovery-Orientated Drug Treatment report, written by an expert working group, and comprises four key phases: engagement and stabilisation, including the establishment of treatment goals; preparation for change, involving engagement in psychosocial and pharmacological interventions; active change, including detoxification and medical withdrawal; and completion, including interventions that strengthen community integration. A body of evidence supports the benefits of buprenorphine, a partial agonist at mu opioid receptors, in supporting individualised recovery based on this framework, specifically in relation to the potential for rapid stabilisation, flexibility to transition to other treatment options or achieve abstinence, effective blocking of on-top use of illicit drugs, the treatment of comorbidities through the minimisation of drug-drug interactions, and a good safety profile. In addition, the newer abuse-deterrent formulation of buprenorphine combined with the opioid antagonist naloxone is likely to strengthen recovery-orientated systems of care due to its potential to reduce misuse and diversion. Progress through the recovery journey and the ability to sustain recovery will depend on individual needs and goals and on the amount of recovery capital that individuals have developed.

Psychiatric services and prescription fills among veterans with serious mental illness in methadone maintenance treatment

OBJECTIVE

Comorbidity and co-prescription patterns of people with serious mental illness in methadone maintenance may complicate their treatment and have not been studied. The goal of this study was to examine the care and characteristics of people with serious mental illness in methadone maintenance treatment nationally in the Veterans Health Administration (VHA).

METHODS

Using national VHA data from FY2012, bivariate and multiple logistic regression analyses were used to compare veterans in methadone maintenance treatment wo had a serious mental illness (schizophrenia, bipolar disorder, or major affective disorder) to patients in methadone maintenance treatment without serious mental illness and patients with serious mental illness who were not in methadone maintenance treatment.

RESULTS

Only a small fraction of patients with serious mental illness were receiving methadone maintenance treatment (0.65%), but a relatively large proportion in methadone maintenance treatment had a serious mental illness (33.2%). Compared to patients without serious mental illness, patients with serious mental illness in methadone maintenance treatment were more likely to have been homeless, to have had a recent psychiatric hospitalization, to be over 50% disabled, and to have had more fills for more classes of psychotropic drugs. Compared to other patients with serious mental illness, patients with serious mental illness in methadone maintenance treatment were more likely to have a drug abuse diagnosis and to reside in large urban areas.

CONCLUSIONS

One-third of patients in methadone maintenance treatment have serious mental illness and more frequent psychiatric comorbidity, and they are more likely to use psychiatric and general health services and fill more types of psychiatric prescriptions. Further study and clinical awareness of potential drug-drug interactions in this high medication and service using population are needed.

The impact of recent cocaine use on plasma levels of methadone and buprenorphine in patients with and without HIV-infection

Cocaine decreases methadone and buprenorphine plasma concentrations. HIV infection and/or antiretroviral medication use may impact these relationships. We sought to determine the association between recent cocaine use and methadone and buprenorphine concentrations in HIV-infected and uninfected subjects in clinical care. R- and S-methadone or buprenorphine and norbuprenorphine concentrations were assessed at 0.5, 1, 2, and 24 hours after dosing in subjects with confirmed cocaine use and abstinence. We compared methadone and buprenorphine concentrations for cocaine use vs. abstinence, by HIV status in 16 subjects receiving methadone (6 HIV-infected) and 17 receiving buprenorphine (8 HIV-infected). With recent cocaine use, peak R-methadone (244 vs. 297 ng/mL, p = 0.03) and peak S-methadone (285 vs. 339 ng/mL); p = 0.03 concentrations were lower in HIV-uninfected subjects only. Peak buprenorphine and norbuprenorphine concentrations were unchanged regardless of cocaine use or HIV status. Cocaine may decrease methadone concentrations in HIV-uninfected subjects. HIV infection or its treatment may attenuate cocaine's effect on methadone.

Buprenorphine for Cancer Pain

Buprenorphine (BUP) is a semisynthetic derivative of the opium alkaloid thebaine found in the poppy Papaver somniferum. Its chemical structure contains the morphine structure but differs by having a cyclopropylmethyl group. Buprenorphine is a potent µ opioid agonist. Buprenorphine undergoes extensive first-pass metabolism in the liver and gut. The development of a transdermal BUP formulation in 2001 led to its evaluation in cancer pain. This article provides the practitioner with an update on the current role of BUP in cancer care. It highlights data suggesting effectiveness in various types of cancer pain. The article reviews pharmacology, routes of administration, adverse effects, drug interactions, and cost considerations.

French 2013 guidelines for antiretroviral therapy of HIV-1 infection in adults

Introduction

These guidelines are part of the French Experts’ recommendations for the management of people living with HIV/AIDS, which were made public and submitted to the French health authorities in September 2013. The objective was to provide updated recommendations for antiretroviral treatment (ART) of HIV-positive adults. Guidelines included the following topics: when to start, what to start, specific situations for the choice of the first session of antiretroviral therapy, optimization of antiretroviral therapy after virologic suppression, and management of virologic failure.

Methods

Ten members of the French HIV 2013 expert group were responsible for guidelines on ART. They systematically reviewed the most recent literature. The chairman of the subgroup was responsible for drafting the guidelines, which were subsequently discussed within, and finalized by the whole expert group to obtain a consensus. Recommendations were graded for strength and level of evidence using predefined criteria. Economic considerations were part of the decision-making process for selecting preferred first-line options. Potential conflicts of interest were actively managed throughout the whole process.

Results

ART should be initiated in any HIV-positive person, whatever his/her CD4 T-cell count, even when >500/mm³. The level of evidence of the individual benefit of ART in terms of mortality or progression to AIDS increases with decreasing CD4 cell count. Preferred initial regimens include two nucleoside reverse transcriptase inhibitors (tenofovir/emtricitabine or abacavir/lamivudine) plus a non-nucleoside reverse transcriptase inhibitor (efavirenz or rilpivirine), or a ritonavir-boosted protease inhibitor (atazanavir or darunavir). Raltegravir, lopinavir/r, and nevirapine are recommended as alternative third agents, with specific indications and restrictions. Specific situations such as HIV infection in women, primary HIV infection, severe immune suppression with or without identified opportunistic infection, and person who injects drugs are addressed. Options for optimization of ART once virologic suppression is achieved are discussed. Evaluation and management of virologic failure are described, the aim of any intervention in such situation being to reduce plasma viral load to <50 copies/ml.

Conclusion

These guidelines recommend that any HIV-positive individual should be treated with ART. This recommendation was issued both for the patient’s own sake and for promoting treatment as prevention.

Antiretroviral medication: an emerging category of prescription drug misuse

BACKGROUND AND OBJECTIVES

Prescription drug abuse has been a focus of public health concern over the past two decades with many studies addressing patterns of narcotic analgesic abuse and diversion. Most research in this domain has centered on controlled substances with known abuse liability. However, the scientific literature has been virtually silent regarding other prescribed medications with previously undocumented addictive potential, such as antiretroviral (ARV) medications for treatment of human immunodeficiency virus.

METHODS

This article reviews the available evidence that suggests a growing problem of ARV diversion and abuse and explores the reasons for the misuse of these medications based on the theoretical neuropsychiatric effects of ARVs and the drug-drug interactions between ARVs and other drugs of abuse.

RESULTS

Review of media reports and qualitative studies suggest that ARV medications are emerging drugs of abuse. Claims about the psychoactive effects of ARV medications are supported by scientific case reports.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

This article reviews the evidence to date of an emerging problem of diversion and misuse of ARV medications for recreational purposes. Implications of ARV misuse and diversion are discussed with suggestions for future research and intervention.

High-sensitivity analysis of buprenorphine, norbuprenorphine, buprenorphine glucuronide, and norbuprenorphine glucuronide in plasma and urine by liquid chromatography-mass spectrometry

A new method using ultra-fast liquid chromatography and tandem mass spectrometry (UFLC-MS/MS) was developed for the simultaneous determination of buprenorphine and the metabolites norbuprenorphine, buprenorphine-3β-glucuronide, and norbuprenorphine-3β-glucuronide in plasma and urine. Sample handling, sample preparation and solid-phase extraction procedures were optimized for maximum analyte recovery. All four analytes of interest were quantified by positive ion electrospray ionization tandem mass spectrometry after solid-phase microextraction. The lower limits of quantification in plasma were 1pg/mL for buprenorphine and buprenorphine glucuronide, and 10pg/mL for norbuprenorphine and norbuprenorphine glucuronide. The lower limits of quantitation in urine were 10pg/mL for buprenorphine, norbuprenorphine and their glucuronides. Overall extraction recoveries ranged from 68-100% in both matrices. Interassay precision and accuracy was within 10% for all four analytes in plasma and within 15% in urine. The method was applicable to pharmacokinetic studies of low-dose buprenorphine.

The next therapeutic challenge in HIV: polypharmacy

With the adoption of combination antiretroviral therapy (ART), most HIV-infected individuals in care are on five or more medications and at risk of harm from polypharmacy, a risk that likely increases with number of medications, age, and physiologic frailty. Established harms of polypharmacy include decreased medication adherence and increased serious adverse drug events, including organ system injury, hospitalization, geriatric syndromes (falls, fractures, and cognitive decline) and mortality. The literature on polypharmacy among those with HIV infection is limited, and the literature on polypharmacy among non-HIV patients requires adaptation to the special issues facing those on chronic ART. First, those aging with HIV infection often initiate ART in their 3rd or 4th decade of life and are expected to remain on ART for the rest of their lives. Second, those with HIV may be at higher risk for age-associated comorbid disease, further increasing their risk of polypharmacy. Third, those with HIV may have an enhanced susceptibility to harm from polypharmacy due to decreased organ system reserve, chronic inflammation, and ongoing immune dysfunction. Finally, because ART is life-extending, nonadherence to ART is particularly concerning. After reviewing the relevant literature, we propose an adapted framework with which to address polypharmacy among those on lifelong ART and suggest areas for future work.

Mechanism of autoinduction of methadone N-demethylation in human hepatocytes

BACKGROUND

There is considerable interindividual and intraindividual variability in methadone metabolism and clearance. Methadone dosing is particularly challenging during initiation of therapy, because of time-dependent increases in hepatic clearance (autoinduction). Although methadone N-demethylation is catalyzed in vitro by cytochrome P4502B6 (CYP2B6) and CYP3A4, and clearance in vivo depends on CYP2B6, mechanism(s) of autoinduction are incompletely understood. In this investigation, we determined mechanism(s) of methadone autoinduction using human hepatocytes.

METHODS

Fresh human hepatocytes were exposed to 0.1 to 10 µM methadone for 72 hours. Cells were washed and methadone N-demethylation assessed. CYP2B6, CYP3A4, and CYP3A5 messenger RNA (mRNA), protein expression (by gel-free high-performance liquid chromatography mass spectrometry) and catalytic activity (bupropion hydroxylation and alfentanil dealkylation for CYP2B6 and CYP3A4/5, respectively) were measured. Mechanisms of CYP induction were characterized using pregnane X receptor and constitutive androstane receptor reporter gene assays.

RESULTS

Methadone (10 µM) increased methadone N-demethylation 2-fold, CYP2B6 and CYP3A4 mRNA 3-fold, and protein expression 2-fold. CYP3A5 mRNA was unchanged. CYP2B6 and CYP3A4/5 activities increased 2-fold. Induction by methadone enantiomers (R-methadone versus S-methadone) did not differ. Induction was relatively weak compared with maximum induction by phenobarbital and rifampin. Lower methadone concentrations had smaller effects. Methadone was an agonist for the pregnane X receptor but not the constitutive androstane receptor.

CONCLUSIONS

Methadone caused concentration-dependent autoinduction of methadone N-demethylation in human hepatocytes, related to induction of CYP2B6 and CYP3A4 mRNA expression, protein expression, and catalytic activity. Induction was related to pregnane X receptor but not constitutive androstane receptor activation. These in vitro findings provide mechanistic insights into clinical autoinduction of methadone metabolism and clearance.

Factors associated with mortality of HIV-positive clients receiving methadone maintenance treatment in China

BACKGROUND

Little is known about mortality of opiate users attending methadone maintenance treatment (MMT) clinics. We sought to investigate mortality and its predictors among human immunodeficiency virus (HIV)-positive MMT clients.

METHODS

Records of 306 786 clients enrolled in China's MMT program from 24 March 2004 to 30 April 2011 were abstracted. Mortality rates were calculated for all HIV-positive antiretroviral treatment (ART)-naive and ART-experienced clients. Risk factors were examined using stratified proportional hazard ratios (HRs).

RESULTS

The observed mortality rate for all clients was 11.8/1000 person-years (PY, 95% confidence interval [CI], 11.5-12.1) and 57.2/1000 PY (CI, 54.9-59.4) for HIV-positive clients (n = 18 193). An increase in average methadone doses to >75 mg/day was associated with a 24% reduction in mortality (HR = 0.76, CI, .70-.82), a 48% reduction for ART-naive HIV-positive clients (HR = 0.52, CI, .42-.65), and a 47% reduction for ART-experienced HIV-positive clients (HR = 0.53, CI, .46-.62). Among ART-experienced clients, initiation of ART when the CD4(+) T-cell count was >300 cells/mm(3) (HR = 0.64, CI, .43-.94) was also associated with decreased risk of death.

CONCLUSIONS

We found high mortality rates among HIV-positive MMT clients, yet decreased risk of death, with earlier ART initiation and higher methadone doses. A higher daily methadone dose was associated with reduced mortality in both HIV-infected and HIV-uninfected clients, independent of ART.

Corrected QT interval during treatment with methadone and buprenorphine--relation to doses and serum concentrations

BACKGROUND

Methadone and buprenorphine are widely used in the treatment of opioid addiction. Some study results suggest that methadone can be associated with QT interval prolongation and torsades de pointes ventricular arrhythmias, whereas no such risk has been observed for buprenorphine. The aim of this study is to determine the risk of corrected QT interval (QTc) increase among patients treated with these medications in an opioid maintenance treatment (OMT) programme, and to study possible associations between QTc changes and serum concentrations of methadone or buprenorphine.

METHODS

Eighty patients enrolled in the OMT programme were followed after start of treatment with methadone (n=45) or buprenorphine (n=35). QTc interval was assessed by electrocardiography (ECG) at baseline and after 1 month (n=79) and 6 months (n=66) in the OMT programme. Blood samples were obtained for the analysis of serum concentrations of buprenorphine, (R)-methadone, (S)-methadone and total methadone.

RESULTS

No patients had QTc prolongation (defined as a QTc value above 450 ms) at baseline or after 1 or 6 months. When analysed in a linear mixed effects model, QTc was not associated with the serum concentrations of buprenorphine or methadone. However, low serum potassium levels increased QTc significantly.

CONCLUSIONS

These results support and extend previous findings that treatment with methadone in modest doses (i.e. below 100mg/d) is not associated with clinically significant QTc increases, and that buprenorphine in commonly used doses is a suitable alternative to methadone with regard to the risk of QTc prolongation.

Pain treatment in patients infected with human immunodeficiency virus in later stages: pharmacological aspects

Pain is a common and debilitating symptom of human immunodeficiency virus (HIV) disease, although it is often underestimated and undertreated, especially in HIV-infected intravenous drug users. It is more likely to occur in the later stages of the HIV disease, where it assumes particular significance, especially in terminally ill patients. However, its successful management is possible, though the goal of effective therapy is hampered by the side effects of highly active antiretroviral therapy and drug-drug interactions. In order to appraise these issues, a search in MEDLINE database was conducted. Book reviews and a search on relevant Web sites were also included. Treatment of HIV is itself very complex and becomes even more difficult when palliative therapy is added. Protease inhibitors, mainly ritonavir, and nonnucleoside reverse transcriptase inhibitors have higher interaction potential, due to their inducer or inhibitory actions on cytochrome P450, posing a risk when coadministered with palliative treatments; so, better outcomes can be achieved with knowledge of pharmacological aspects.

Psychiatric comorbidity in injecting drug users in Asia and Africa

PURPOSE OF REVIEW

The prevalence of psychiatric co-morbidity in injecting drug users (IDUs) in the Western countries is high and is associated with lower quality of life and reduces the effectiveness of treatment programs. The aim of this study is to provide a review about psychiatric comorbidity in IDUs in Asia and Africa, where HIV prevalence is high and still increasing.

RECENT FINDINGS

Studies focusing on psychiatric comorbidity in Asia and Africa are scarce. The prevalence of psychiatric comorbidity is comparable with the prevalence in western countries. Psychiatric disorders can occur before or during drug abuse and are also associated with substance abuse and physical comorbidity and its treatments. Childhood trauma followed by post-traumatic disorders is a significant risk factor for substance abuse. Psychiatric co-occurring disorders influence the adherence to the physical and drug use treatment. Evidence-based treatment for psychiatric comorbidity in IDUs is still limited.

SUMMARY

A better understanding of the prevalence of psychiatric disorders in IDUs and its impact on the overall treatments is growing. However, more studies focusing on the treatment for psychiatric comorbidity in IDUs in Asia and Africa are needed.

Mechanism of efavirenz influence on methadone pharmacokinetics and pharmacodynamics

Mechanisms by which efavirenz diminishes methadone plasma concentrations are unknown. This investigation determined efavirenz influence on clinical methadone disposition and miosis, intravenous and oral alfentanil clearance (hepatic and intestinal cytochrome P450 3A4/5 (CYP3A4/5) activity), fexofenadine disposition (intestinal transporters activity), and efavirenz clearance and 8-hydroxylation (CYP2B6 activity), and human hepatocyte effects. Efavirenz induced systemic and oral alfentanil clearances two- to fivefold and induced efavirenz 8-hydroxylation. Efavirenz stereoselectively decreased methadone plasma concentrations 50-70%. Methadone systemic and oral clearances, hepatic clearance and extraction ratio, N-demethylation, and metabolite formation clearance were stereoselectively increased two- to threefold. Bioavailability decreased. Efavirenz shifted methadone concentration-miosis curves leftward and upward. Efavirenz induced hepatocyte CYP2B6 and CYP3A4 expression, activity, and methadone N-demethylation. Results show that efavirenz coinduced hepatic CYP2B6 and CYP3A4/5, coinduced hepatic and intestinal CYP3A4/5, and coinduced gastrointestinal CYP3A4/5 and efflux transporters. Methadone disposition was most consistent with efavirenz induction of hepatic CYP2B6-mediated methadone N-demethylation. Efavirenz may alter methadone pharmacodynamics.

HIV infection and risk of overdose: a systematic review and meta-analysis

Drug overdose is a common cause of non-AIDS death among people with HIV and the leading cause of death for people who inject drugs. People with HIV are often exposed to opioid medications during their HIV care experience; others may continue to use illicit opioids despite their disease status. In either situation, there may be a heightened risk for nonfatal or fatal overdose. The potential mechanisms for this elevated risk remain controversial. We systematically reviewed the literature on the HIV-overdose association, meta-analyzed results, and investigated sources of heterogeneity, including study characteristics related to hypothesize biological, behavioral, and structural mechanisms of the association. Forty-six studies were reviewed, 24 of which measured HIV status serologically and provided data quantifying an association. Meta-analysis results showed that HIV seropositivity was associated with an increased risk of overdose mortality (pooled risk ratio 1.74, 95% confidence interval 1.45, 2.09), although the effect was heterogeneous (Q = 80.3, P < 0.01, I(2) = 71%). The wide variability in study designs and aims limited our ability to detect potentially important sources of heterogeneity. Causal mechanisms considered in the literature focused primarily on biological and behavioral factors, although evidence suggests structural or environmental factors may help explain the greater risk of overdose among HIV-infected drug users. Gaps in the literature for future research and prevention efforts as well as recommendations that follow from these findings are discussed.

Lack of indinavir effects on methadone disposition despite inhibition of hepatic and intestinal cytochrome P4503A (CYP3A)

BACKGROUND

Methadone disposition and pharmacodynamics are highly susceptible to interactions with antiretroviral drugs. Methadone clearance and drug interactions have been attributed to cytochrome P4503A4 (CYP3A4), but actual mechanisms are unknown. Drug interactions can be clinically and mechanistically informative. This investigation assessed effects of the protease inhibitor indinavir on methadone pharmacokinetics and pharmacodynamics, hepatic and intestinal CYP3A4/5 activity (using alfentanil), and intestinal transporter activity (using fexofenadine).

METHODS

Twelve healthy volunteers underwent a sequential crossover. On three consecutive days they received oral alfentanil plus fexofenadine, intravenous alfentanil, and intravenous plus oral (deuterium-labeled) methadone. This was repeated after 2 weeks of indinavir. Plasma and urine analytes were measured by mass spectrometry. Opioid effects were measured by miosis.

RESULTS

Indinavir significantly inhibited hepatic and first-pass CYP3A activity. Intravenous alfentanil systemic clearance and hepatic extraction were reduced to 40-50% of control, apparent oral clearance to 30% of control, and intestinal extraction decreased by half, indicating 50% and 70% inhibition of hepatic and first-pass CYP3A activity. Indinavir increased fexofenadine area under the plasma concentration-time curve 3-fold, suggesting significant P-glycoprotein inhibition. Indinavir had no significant effects on methadone plasma concentrations, methadone N-demethylation, systemic or apparent oral clearance, renal clearance, hepatic extraction or clearance, or bioavailability. Methadone plasma concentration-effect relationships were unaffected by indinavir.

CONCLUSIONS

Despite significant inhibition of hepatic and intestinal CYP3A activity, indinavir had no effect on methadone N-demethylation and clearance, suggesting little or no role for CYP3A in clinical disposition of single-dose methadone. Inhibition of gastrointestinal transporter activity had no influence of methadone bioavailability.

Therapeutic drug monitoring of protease inhibitors and efavirenz in HIV-infected individuals with active substance-related disorders

BACKGROUND

Achieving targeted antiretroviral (ARV) plasma concentrations during long-term treatment in human immunodeficiency virus (HIV)-infected patients with substance-related disorders (SRDs) may be challenging due to a number of factors, including medication adherence, coinfection with hepatitis B or C virus, medication intolerance, and drug interactions. One approach to investigate these factors is to conduct therapeutic drug monitoring to measure ARV exposure during treatment. The objective of this study was to utilize therapeutic drug monitoring to compare efavirenz (EFV) and protease inhibitor pharmacokinetics in patients with and without SRDs.

METHODS

This was a multicenter, cross-sectional open-label study in patients with HIV-1 infection receiving antiretroviral therapy (ART), with active (n=129) or without (n=146) SRD according to National Institute on Drug Abuse criteria. Two hundred seventy-five subjects who were receiving either protease inhibitor-based or EFV-based ART regimens for >6 months were enrolled at 4 HIV treatment centers with an equal distribution of SRD and non-SRD at each site. The patients were instructed during enrollment visits with regard to the importance of adherence before and after study visits. Demographics and routine clinical laboratory tests were recorded.

RESULTS

Among the 275 patients, 47% had SRD with at least 1 substance. There were no significant differences between SRD and non-SRD groups for race, gender, age, or CD4 count at entry. A significantly higher proportion of patients with SRD had an entry HIV RNA plasma concentration>75 copies per milliliter compared with patients without SRD (40% vs 28%, P=0.044). Logistic regression modeling revealed an association between HIV RNA plasma concentration and African American race (P=0.017). A significantly higher proportion of SRDs also had an EFV or protease inhibitor trough concentration below the desired range (23% vs 9%, P=0.048). Significantly lower trough concentrations were noted in patients with SRDs receiving atazanavir (0.290 vs 0.976 μg/mL) or lopinavir (3.75 vs 5.30 μg/mL).

CONCLUSIONS

The pharmacokinetic data indicate differences between HIV-infected patients with and without SRDs that may influence viral load suppression during long-term ART. These findings require additional investigation in a randomized design with more intensive pharmacokinetic assessment to identify individual factors that are contributing to suboptimal ARV exposure in patients with SRDs.

The World Federation of Societies of Biological Psychiatry (WFSBP) guidelines for the biological treatment of substance use and related disorders. Part 2: Opioid dependence

OBJECTIVES

To develop evidence-based practice guidelines for the pharmacological treatment of opioid abuse and dependence.

METHODS

An international task force of the World Federation of Societies of Biological Psychiatry (WFSBP) developed these practice guidelines after a systematic review of the available evidence pertaining to the treatment of opioid dependence. On the basis of the evidence, the Task Force reached a consensus on practice recommendations, which are intended to be clinically and scientifically meaningful for physicians who treat adults with opioid dependence. The data used to develop these guidelines were extracted primarily from national treatment guidelines for opioid use disorders, as well as from meta-analyses, reviews, and publications of randomized clinical trials on the efficacy of pharmacological and other biological treatments for these disorders. Publications were identified by searching the MEDLINE database and the Cochrane Library. The literature was evaluated with respect to the strength of evidence for efficacy, which was categorized into one of six levels (A-F).

RESULTS

There is an excellent evidence base supporting the efficacy of methadone and buprenorphine or the combination of buprenorphine and naloxone for the treatment of opioid withdrawal, with clonidine and lofexidine as secondary or adjunctive medications. Opioid maintenance with methadone and buprenorphine is the best-studied and most effective treatment for opioid dependence, with heroin and naltrexone as second-line medications.

CONCLUSIONS

There is enough high quality data to formulate evidence-based guidelines for the treatment of opioid abuse and dependence. This task force report provides evidence for the efficacy of a number of medications to treat opioid abuse and dependence, particularly the opioid agonists methadone or buprenorphine. These medications have great relevance for clinical practice.