The pharmacokinetics of heroin in patients with chronic pain

Blood Oxygenation and Heart Rate Changes After Diamorphine Intravenous Injection During Opioid Agonist Treatment for Outpatients With Heroin Dependence

OBJECTIVES

More than 60 million people use opioids each year, and many countries have declared an opioid overdose crisis. Heroin, one of the most commonly used opioids, has depressant effects on autonomic functioning; however, few studies have been able to examine the effects of heroin or its pharmaceutically prepared equivalent, diamorphine, in human clinical populations. The present study examined heart rate and oxygen saturation in the minutes immediately after acute diamorphine administration in outpatients with heroin dependence.

METHODS

The sample was a subset of participants (N = 36) in the German Project of Heroin Assisted Treatment of Opiate Dependent Patients Trial in Bonn, Germany. Patients were given 3 daily doses of intravenous diamorphine. Doses were determined on an individual basis by study physicians. Pulse oximetry was recorded at baseline and at 30-second intervals from 0 to 450 seconds after diamorphine administration.

RESULTS

Heart rate was significantly higher than baseline at 30 seconds after diamorphine administration and significantly lower than baseline at 270 seconds onward. Oxygen saturation was significantly lower than baseline at 60 seconds onward.

CONCLUSIONS

Results are consistent with other studies in which depressant effects of opioids were observed. Our findings suggest that even therapeutic doses of diamorphine may have rapid and significant-predominantly depressant-effects on oxygenation and heart rate in populations that frequently use opioids. Monitoring of potential adverse opioid effects would be beneficial even in populations presumed to have developed physiological tolerance.

Heroin metabolism in human blood and its impact for the design of an immunotherapeutic approach against heroin effects

Immunotherapeutic interventions that block drug effects by binding drug molecules to specific antibodies in the bloodstream have shown promising effects in animal studies. For heroin, which effects are mainly mediated by the metabolites 6-acetylmorphine (6-AM; also known as 6-monoacetylmorphine or 6-MAM) and morphine, the optimal antibody specificity has been discussed. In rodents, 6-AM specific antibodies have been recommended based on the rapid metabolism of heroin to 6-AM in the bloodstream. Since the metabolic rate of heroin in blood is unsettled in humans, we examined heroin metabolism with state-of-the-art analytical methodology (UHPLC-MS/MS) in freshly drawn human whole blood incubated with a wide range of heroin concentrations (1-500 μM). The half-life of heroin was highly concentration dependent, ranging from 1.2-1.7 min for concentrations at or above 25 μM, and gradually increasing to approximately 20 min for 1 μM heroin. At concentrations that can be attained in the bloodstream shortly after an i.v. injection, approximately 70% was transformed into 6-AM within 3 min, similar to previous observations in vivo. Our results indicate that blood enzymes play a more important role for the rapid metabolism of heroin in humans than previously assumed. This points to 6-AM as an important target for an efficient immunotherapeutic approach to block heroin effects in humans.

Heroin and its metabolites: relevance to heroin use disorder

Heroin is an opioid agonist commonly abused for its rewarding effects. Since its synthesis at the end of the nineteenth century, its popularity as a recreational drug has ebbed and flowed. In the last three decades, heroin use has increased again, and yet the pharmacology of heroin is still poorly understood. After entering the body, heroin is rapidly deacetylated to 6-monoacetylmorphine (6-MAM), which is then deacetylated to morphine. Thus, drug addiction literature has long settled on the notion that heroin is little more than a pro-drug. In contrast to these former views, we will argue for a more complex interplay among heroin and its active metabolites: 6-MAM, morphine, and morphine-6-glucuronide (M6G). In particular, we propose that the complex temporal pattern of heroin effects results from the sequential, only partially overlapping, actions not only of 6-MAM, morphine, and M6G, but also of heroin per se, which, therefore, should not be seen as a mere brain-delivery system for its active metabolites. We will first review the literature concerning the pharmacokinetics and pharmacodynamics of heroin and its metabolites, then examine their neural and behavioral effects, and finally discuss the possible implications of these data for a better understanding of opioid reward and heroin addiction. By so doing we hope to highlight research topics to be investigated by future clinical and pre-clinical studies.

The suitability of oral diacetylmorphine in treatment-refractory patients with heroin dependence: A scoping review

OBJECTIVE

To review the scientific literature on the pharmacokinetics, pharmacodynamics and clinical efficacy and safety of (supervised) oral diacetylmorphine for patients with severe heroin dependence.

METHODS

The PubMed, Embase, Web of Science and PsycINFO databases were searched. Eleven published studies were identified and selected based on defined eligibility and exclusion criteria.

RESULTS

Four pharmacokinetic studies reported negligible plasma concentrations of diacetylmorphine and its active metabolite 6-monacetylmorphine. Among six pharmacodynamic studies, three trials showed that oral diacetylmorphine reduced opioid withdrawal symptoms, one open-label pilot study reported that two patients experienced a modest 'rush' after oral diacetylmorphine and two studies found that patients could not distinguish between oral diacetylmorphine, methadone, or morphine. Regarding the clinical studies, a Swiss prospective cohort study in patients with heroin dependence showed high retention rates of oral diacetylmorphine treatment with few serious adverse events, whereas in the Canadian SALOME trial, oral diacetylmorphine treatment was prematurely discontinued because treatment retention of oral diacetylmorphine was lower than injectable diacetylmorphine maintenance treatment. Finally, two case studies illustrate the limitations and potential problems of oral diacetylmorphine in the treatment of treatment-refractory heroin dependent patients.

CONCLUSIONS

Based on all published data, it is unlikely that oral diacetylmorphine produces a substantial 'rush'. Prescription of oral diacetylmorphine might therefore be effective only for treatment-refractory patients with heroin dependence (i) as maintenance treatment for those who never injected or inhaled opioids; (ii) as maintenance treatment for those who want to switch from injection to oral administration of diacetylmorphine; and/or (iii) to reduce opioid withdrawal symptoms.

The effect of depressive symptoms on pain in a substance-using population with persistent pain: a cross-sectional cohort study

BACKGROUND

In light of the ongoing opioid overdose crisis, there is an urgent need for research on the impacts of mental health among people presenting with concurrent pain and substance use. This study examined the effect of depressive symptoms on pain severity and functional interference among people who use drugs (PWUD) during a community-wide overdose crisis.

METHODS

From December 1st 2016 to December 31st 2018, 288 participants in two cohort studies of PWUD in Vancouver, Canada completed interviewer-administered questionnaires that included the Brief Pain Inventory and PROMIS Emotional Distress-Depression instruments. Generalized linear regression modelling (GLM) was used to examine the cross-sectional effect of depressive symptoms and other confounding factors on pain severity and interference.

RESULTS

Moderate to severe depressive symptoms were significantly associated with greater pain-related functional interference (adjusted β = 1.24, 95% confidence interval [CI] = 0.33-2.15), but not significantly associated with greater average pain severity (adjusted β = 0.22, 95% CI = - 0.3 - 0.82), when controlling for confounding variables. Reported daily heroin use (adjusted β = 1.26, 95% CI = 0.47-2.05) and non-fatal overdose (adjusted β = 1.02, 95% CI = 0.08-1.96) were also significantly associated with greater pain-related functional interference.

CONCLUSIONS

In a substance-using population, greater pain-related functional interference was positively associated with depressive symptoms as well as overdose and daily heroin use. These findings emphasize the need to address the functional impact of pain, mental health comorbidity, and high-risk substance use that may contribute to overdose and other harms.

DARK Classics in Chemical Neuroscience: Heroin and Desomorphine

Opioids are arguably one of the most important pharmacologic classes, mainly due to their rich history, their useful and potent analgesic effects, and also, just as importantly, their "Dark Side", constituted by their reinforcing properties that have led countless of users to a spiral of addiction, biological dependence, tolerance, withdrawal syndromes, and death. Among the most significant abused and addictive known opioids are heroin and desomorphine, both synthetic derivatives of morphine that belong to the 4,5-epoxymorphinan structural chemical group of the opioid family drugs. These agents share not only structural, pharmacological, and epidemiological features but also a common geographical distribution. A drop in Afghan heroin production and its "exports" to Russia gave rise to widespread consumption of desomorphine in ex-Soviet republics during the first decade of the 21st century, representing an economical and accessible alternative for misusers to this sort of derivative. Herein we review the state of the art of history, chemistry and synthesis, pharmacology, and impact on society of these "cursed cousins".

Preclinical Evaluation of Vaccines to Treat Opioid Use Disorders: How Close are We to a Clinically Viable Therapeutic?

The ongoing opioid crisis, now into its second decade, represents a global public health challenge. Moreover, the opioid crisis has manifested despite clinical access to three approved opioid use disorder medications: the full opioid agonist methadone, the partial opioid agonist buprenorphine, and the opioid antagonist naltrexone. Although current opioid use disorder medications are underutilized, the ongoing opioid crisis has also identified the need for basic research to develop both safer and more effective opioid use disorder medications. Emerging preclinical evidence suggests that opioid-targeted vaccines or immunopharmacotherapies may be promising opioid use disorder therapeutics. One premise for this article is to critically examine whether vaccine effectiveness evaluated using preclinical antinociceptive endpoints is predictive of vaccine effectiveness on abuse-related endpoints such as drug self-administration, drug discrimination, and conditioned place preference. A second premise is to apply decades of knowledge in the preclinical evaluation of candidate small-molecule therapeutics for opioid use disorder to the preclinical evaluation of candidate opioid use disorder immunopharmacotherapies. We conclude with preclinical experimental design attributes to enhance preclinical-to-clinical translatability and potential future directions for immunopharmacotherapies to address the dynamic illicit opioid environment.

Indices of dentate gyrus neurogenesis are unaffected immediately after or following withdrawal from morphine self-administration compared to saline self-administering control male rats

Opiates - including morphine - are powerful analgesics with high abuse potential. In rodents, chronic opiate exposure or self-administration negatively impacts hippocampal-dependent function, an effect perhaps due in part to the well-documented opiate-induced inhibition of dentate gyrus (DG) precursor proliferation and neurogenesis. Recently, however, intravenous (i.v.) morphine self-administration (MSA) was reported to enhance the survival of new rat DG neurons. To reconcile these disparate results, we used rat i.v. MSA to assess 1) whether a slightly-higher dose MSA paradigm also increases new DG neuron survival; 2) how MSA influences cells in different stages of DG neurogenesis, particularly maturation and survival; and 3) if MSA-induced changes in DG neurogenesis persist through a period of abstinence. To label basal levels of proliferation, rats received the S-phase marker bromodeoxyuridine (BrdU, i.p.) 24 -h prior to 21 days (D) of i.v. MSA or saline self-administration (SSA). Either immediately after SA (0-D) or after 4 weeks in the home cage (28-D withdrawal), stereology was used to quantify DG proliferating precursors (or cells in cell cycle; Ki67+ cells), neuroblast/immature neurons (DCX+ cells), and surviving DG granule cells (BrdU+ cells). Analysis revealed the number of DG cells immunopositive for these neurogenesis-relevant markers was similar between MSA and SSA rats at the 0-D or 28-D timepoints. These negative data highlight the impact experimental parameters, timepoint selection, and quantification approach have on neurogenesis results, and are discussed in the context of the large literature showing the negative impact of opiates on DG neurogenesis.

The influence of carboxylesterase 1 polymorphism and cannabidiol on the hepatic metabolism of heroin

Heroin (diamorphine) is a highly addictive opioid drug synthesized from morphine. The use of heroin and incidence of heroin associated overdose death has increased sharply in the US. Heroin is primarily metabolized via deacetylation (hydrolysis) forming the active metabolites 6-monoacetylmorphine (6-MAM) and morphine. A diminution in heroin hydrolysis is likely to cause higher drug effects and toxicities. In this study, we sought to determine the contribution of the major hepatic hydrolase carboxylesterase 1 (CES1) to heroin metabolism in the liver as well as the potential influence of one of its known genetic variants, G143E (rs71647871). Furthermore, given the potential therapeutic application of cannabidiol (CBD) for heroin addiction and the frequent co-abuse of cannabis and heroin, we also assessed the effects of CBD on heroin metabolism. In vitro systems containing human liver, wild-type CES1, and G143E CES1 S9 fractions were utilized in the assessment. The contribution of CES1 to the hydrolysis of heroin to 6-MAM was determined as 3.66%, and CES1 was unable to further catalyze 6-MAM under our assay conditions. The G143E variant showed a 3.2-fold lower intrinsic clearance of heroin as compared to the WT. CBD inhibited heroin and 6-MAM hydrolysis in a reversible manner, with IC₅₀s of 14.7 and 12.1 μM, respectively. Our study results suggested only minor involvement of CES1 in heroin hydrolysis in the liver. Therefore, the G143E variant is unlikely to cause significant impact despite a much lower hydrolytic activity. CBD exhibited potent in vitro inhibition toward both heroin and 6-MAM hydrolysis, which may be of potential clinical relevance.

Diagnosis of acute intoxications in critically ill patients: focus on biomarkers - part 1: epidemiology, methodology and general overview

Acute intoxications account for a significant proportion of the patient population in intensive care units and sedative medications, ethanol, illicit drugs, inhalable poisons and mixed intoxications are the most common causes. The aim of this article is to describe biomarkers for screening and diagnosis of acute intoxications in critically ill patients. For this purpose, a survey of the relevant literature was conducted, and guidelines, case reports, expert assessments, and scientific publications were reviewed. In critical care, it should always be attempted to identify and quantify the poison or toxin with the assistance of enzyme immunoassay (EIA), chromatography, and mass spectrometry techniques and this section is critically appraised in this publication. The principles for anion gap, osmol gap and lactate gap and their usage in intoxications is shown. Basic rules in test methodology and pre-analytics are reviewed. Biomarkers in general are presented in part one and biomarkers for specific intoxications including ethanol, paracetamol, cardiovascular drugs and many others are presented in part two of these publications.

Effectiveness and selectivity of a heroin conjugate vaccine to attenuate heroin, 6-acetylmorphine, and morphine antinociception in rats: Comparison with naltrexone

BACKGROUND

One emerging strategy to address the opioid crisis includes opioid-targeted immunopharmacotherapies. This study compared effectiveness of a heroin-tetanus toxoid (TT) conjugate vaccine to antagonize heroin, 6-acetylmorphine (6-AM), morphine, and fentanyl antinociception in rats.

METHODS

Adult male and female Sprague Dawley rats received three doses of active or control vaccine at weeks 0, 2, and 4. Vaccine pharmacological selectivity was assessed by comparing opioid dose-effect curves in 50 °C  warm-water tail-withdrawal procedure before and after active or control heroin-TT vaccine. Route of heroin administration [subcutaneous (SC) vs. intravenous [IV)] was also examined as a determinant of vaccine effectiveness. Continuous naltrexone treatment (0.0032-0.032 mg/kg/h) effects on heroin, 6-AM, and morphine antinociceptive potency were also determined as a benchmark for minimal vaccine effectiveness.

RESULTS

The heroin-TT vaccine decreased potency of SC heroin (5-fold), IV heroin (3-fold), and IV 6-AM (3-fold) for several weeks without affecting IV morphine or SC and IV fentanyl potency. The control vaccine did not alter potency of any opioid. Naltrexone dose-dependently decreased antinociceptive potency of SC heroin, and treatment with 0.01 mg/kg/h naltrexone produced similar, approximate 8-fold decreases in potencies of SC and IV heroin, IV 6-AM, and IV morphine. The combination of naltrexone and active vaccine was more effective than naltrexone alone to antagonize SC heroin but not IV heroin.

CONCLUSIONS

The heroin-TT vaccine formulation examined is less effective, but more selective, than chronic naltrexone to attenuate heroin antinociception in rats. Furthermore, these results provide an empirical framework for future preclinical opioid vaccine research to benchmark effectiveness against naltrexone.

Current status of opioid addiction treatment and related preclinical research

Opioid use disorders (OUDs) are diseases of the brain with behavioral, psychological, neurobiological, and medical manifestations. Vulnerability to OUDs can be affected by factors such as genetic background, environment, stress, and prolonged exposure to μ-opioid agonists for analgesia. Two standard-of-care maintenance medications, methadone and buprenorphine-naloxone, have a long-term positive influence on health of persons with opioid addiction. Buprenorphine and another medication, naltrexone, have also been approved for administration as monthly depot injections. However, neither medication is used as widely as needed, due largely to stigma, insufficient medical education or training, inadequate resources, and inadequate access to treatment. Ongoing directions in the field include (i) personalized approaches leveraging genetic factors for prediction of OUD vulnerability and prognosis, or for targeted pharmacotherapy, and (ii) development of novel analgesic medicines with new neurobiological targets with reduced abuse potential, reduced toxicity, and improved effectiveness, especially for chronic pain states other than cancer pain.

Opioid Addiction, Genetic Susceptibility, and Medical Treatments: A Review

Opioid addiction is a chronic and complex disease characterized by relapse and remission. In the past decade, the opioid epidemic or opioid crisis in the United States has raised public awareness. Methadone, buprenorphine, and naloxone have proven their effectiveness in treating addicted individuals, and each of them has different effects on different opioid receptors. Classic and molecular genetic research has provided valuable information and revealed the possible mechanism of individual differences in vulnerability for opioid addiction. The polygenic risk score based on the results of a genome-wide association study (GWAS) may be a promising tool to evaluate the association between phenotypes and genetic markers across the entire genome. A novel gene editing approach, clustered, regularly-interspaced short palindromic repeats (CRISPR), has been widely used in basic research and potentially applied to human therapeutics such as mental illness; many applications against addiction based on CRISPR are currently under research, and some are successful in animal studies. In this article, we summarized the biological mechanisms of opioid addiction and medical treatments, and we reviewed articles about the genetics of opioid addiction, the promising approach to predict the risk of opioid addiction, and a novel gene editing approach. Further research on medical treatments based on individual vulnerability is needed.

Historical Review: Opiate Addiction and Opioid Receptors

Substance use disorders (SUDs), defined as a collection of symptoms including tolerance and withdrawal, are chronic illnesses characterized by relapse and remission. In the United States, billions of dollars have been lost due to SUDs. In the past 30 years, effective medications and behavioral interventions have played a major role in preventing relapse and facilitating longer periods of abstinence. From the late 1990s to the present, the opioid epidemic or opioid crisis in the United States has raised public awareness of SUDs. Methadone, buprenorphine, and naloxone have proven their effectiveness in treating addicted individuals, and each of them has different effects on different opioid receptors. Methadone and buprenorphine target mu opioid receptors (MORs) in the brain to treat opioid dependence by reducing withdrawal and craving, whereas naloxone is an opioid antagonist used to treat opioid overdose. Mu, kappa, and delta are opioid receptor subtypes with common analgesic effects, and each also has unique effects and distribution in the brain. MORs in distinct brain regions, such as the nucleus accumbens and basolateral amygdala, trigger the euphoria and incentive properties of rewarding stimuli. Kappa opioid receptors can trigger anti-reward effects and produce dysphoric effects. Delta opioid receptors can induce anxiolytic effects. Though effective medications are available, relapse is still common due to neurobiological changes in brain pathways and tolerance of opioid receptors with repeated abuse of substances. In this article, I summarize the biological mechanisms of opioid dependence and opioid receptors and review previous articles about medications used to treat SUDs and their clinical effects.

Take-home naloxone treatment for opioid emergencies: a comparison of routes of administration and associated delivery systems

INTRODUCTION

Naloxone reversal of opioid-induced respiratory depression outside of medical facilities has become more prevalent because of the escalating opioid epidemic in the USA. Take-home naloxone for treatment of opioid emergencies is now being recommended by numerous federal, state, and professional organizations. Areas covered: The scope of the opioid overdose epidemic is reviewed along with practical, clinical, regulatory, and usability considerations for take-home naloxone routes of administration currently available and associated delivery systems. Specific opioid-related factors are discussed in detail with emphasis placed on life-threatening respiratory depression and naloxone antagonism. A clinical overview, including pharmacokinetic and FDA approval information for each take-home naloxone product is discussed in detail as well as the impact of take-home naloxone in the community. Finally, given these products are to be used in a panic-stricken, life-threatening opioid emergency, an analysis of available usability data is provided with proposed directions for further study. Expert opinion: Based on the available clinical evidence, auto-injectable naloxone should be the preferred administration route for take-home naloxone treatment until additional safety, efficacy, and comparative outcomes data are available for unconventional routes of administration that unequivocally provide equal or superior results.

Identifying cases of heroin toxicity where 6-acetylmorphine (6-AM) is not detected by toxicological analyses

PURPOSE

Heroin has a half-life of 2-6 min and is metabolized too quickly to be detected in autopsy samples. The presence of 6-acetylmophine (6-AM) in urine, blood, or other samples is convincing evidence of heroin use by a decedent, but 6-AM itself has a half-life of 6-25 min before it is hydrolyzed to morphine, so 6-AM may not be present in sufficient concentration to detect in postmortem samples. Codeine is often present in heroin preparations as an impurity and is not a metabolite of heroin. Studies report that a ratio of morphine to codeine greater than one indicates heroin use. We hypothesize that the ratio of morphine to codeine in our decedents abusing drugs intravenously will be no different in individuals with 6-AM present than in individuals where no 6-AM is detected, and we report our study of this hypothesis.

METHODS

All accidental deaths investigated by the Jefferson County Coroner/Medical Examiner Office from 2010 to 2013 with morphine detected in blood samples collected at autopsy were reviewed. Five deaths where trauma caused or contributed to death were excluded from the review. The presence or absence of 6-AM and the concentrations of morphine and codeine were recorded for each case. The ratio of morphine to codeine was calculated for all decedents. Any individual in whom no morphine or codeine was detected in a postmortem sample was excluded from further study. Absence or presence of drug paraphernalia or evidence of intravascular (IV) drug use was documented in each case to identify IV drug users. The proportion of the IV drug users with and without 6-AM present in a postmortem sample was compared to the M/C ratio for the individuals.

RESULTS

Of the 230 deaths included in the analysis, 103 IV drug users with quantifiable morphine and codeine in a postmortem sample were identified allowing for calculation of an M/C ratio. In these IV drug users, the M/C ratio was greater than 1 in 98 % of decedents. When controlling for the absence or presence of 6-AM there was no statistically significant difference in the proportion of IV drug users when compared to non IV drug users with an M/C ratio of greater than 1 (p = 1.000).

CONCLUSION

The M/C ratio in IV drug users, if greater than 1, is seen in deaths due to heroin toxicity where 6-AM is detected in a postmortem sample. This study provides evidence that a M/C ratio greater than one in an IV drug user is evidence of a death due to heroin toxicity even if 6-AM is not detected in the blood. Using the M/C ratio, in addition to scene and autopsy findings, provides sufficient evidence to show heroin is the source of the morphine and codeine. Listing heroin as a cause or contributing factor in deaths with evidence of IV drug abuse and where the M/C ratio exceeds 1 will improve identification of heroin fatalities, which will allow better allocation of resources for public health initiatives.

The toxicology of heroin-related death: estimating survival times

BACKGROUND AND AIMS

The feasibility of intervention in heroin overdose is of clinical importance. The presence of 6-monoacetyl morphine (6MAM) in the blood is suggestive of survival times of less than 20-30 minutes following heroin administration. The study aimed to determine the proportions of cases in which 6MAM was present, and compare concentrations of secondary metabolites and circumstances of death by 6MAM status.

DESIGN

Analysis of cases of heroin-related death presenting to the Department of Forensic Medicine Sydney, 1 January 2013-12 December 2014.

SETTING

Sydney, Australia.

CASES

A total of 145 cases. The mean age was 40.5 years and 81% were male.

MEASUREMENTS

Concentrations of 6MAM, free morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). Circumstances of death included bronchopneumonia, apparent sudden collapse, location and other central nervous system (CNS) depressants.

FINDINGS

6MAM was detected in 43% [confidence interval (CI) = 35-51%] of cases. The median free morphine concentration of 6MAM-positive cases was more than twice that of cases without 6MAM (0.26 versus 0.12 mg/l). 6MAM-positive cases also had lower concentrations of the other major heroin metabolites: M3G (0.05 versus 0.29 mg/l), M6G (0.02 versus 0.05 mg/l) with correspondingly lower M3G/morphine (0.54 versus 2.71) and M6G/morphine (0.05 versus 0.50) ratios. Significant independent correlates of 6MAM were a higher free morphine concentration [odds ratio (OR) = 1.7], a lower M6G/free morphine ratio (OR = 0.5) and signs of apparent collapse (OR = 6.7).

CONCLUSIONS

In heroin-related deaths in Sydney, Australia during 2013 and 2014, 6- monoacetyl morphine was present in the blood in less than half of cases, suggesting that a minority of cases had survival times after overdose of less than 20-30 minutes. The toxicology of heroin metabolites and the circumstances of death were consistent with 6- monoacetyl morphine as a proxy for a more rapid death.

The behavioral effects of acute Δ⁹-tetrahydrocannabinol and heroin (diacetylmorphine) exposure in adult zebrafish

The use of psychotropic drugs in clinical and translational brain research continues to grow, and the need for novel experimental models and screens is becoming widely recognized. Mounting evidence supports the utility of zebrafish (Danio rerio) for studying various pharmacological manipulations, as an alternative model complementing the existing rodent paradigms in this field. Here, we explore the effects of acute 20-min exposure to two commonly abused psychotropic compounds, Δ(9)-tetrahydrocannabinol (THC) and heroin, on adult zebrafish behavior in the novel tank test. Overall, THC administration (30 and 50 mg/L) produces an anxiogenic-like reduction of top swimming, paralleled with a slower, continuous bottom swimming. In contrast, heroin exposure (15 and 25 mg/L) evoked a hyperlocomotor response (with rapid bouts of bottom swimming and frequent 'bouncing' motions) without altering anxiety-sensitive top/bottom endpoints. The behavioral effects of these two compounds in zebrafish seem to parallel the respective rodent and human findings. Collectively, this emphasizes the growing significance of novel emerging aquatic models in translational drug abuse research and small molecule screening.

Mu opioids and their receptors: evolution of a concept

Opiates are among the oldest medications available to manage a number of medical problems. Although pain is the current focus, early use initially focused upon the treatment of dysentery. Opium contains high concentrations of both morphine and codeine, along with thebaine, which is used in the synthesis of a number of semisynthetic opioid analgesics. Thus, it is not surprising that new agents were initially based upon the morphine scaffold. The concept of multiple opioid receptors was first suggested almost 50 years ago (Martin, 1967), opening the possibility of new classes of drugs, but the morphine-like agents have remained the mainstay in the medical management of pain. Termed mu, our understanding of these morphine-like agents and their receptors has undergone an evolution in thinking over the past 35 years. Early pharmacological studies identified three major classes of receptors, helped by the discovery of endogenous opioid peptides and receptor subtypes-primarily through the synthesis of novel agents. These chemical biologic approaches were then eclipsed by the molecular biology revolution, which now reveals a complexity of the morphine-like agents and their receptors that had not been previously appreciated.

'Lingering' opiate deaths? Concentration of opiates in medulla and femoral blood

'Lingering death' cases occur when the circumstances of death indicate an opiate overdose, but measured opiate blood levels are only in the therapeutic range; death results from cardiac and respiratory depression. This study examined the relative concentration of opiates in femoral blood and in the medulla oblongata (sites for cardiac and respiratory control) from 41 cases to determine whether a difference in opiate concentration might explain lingering deaths. Opiates from blood and medulla were analyzed using GC-EI-MS in selective ion monitoring mode. Results were correlated with gross and microscopic findings of the lungs and with cause and manner of death. Opiate concentrations for morphine, codeine and 6-acetylmorphine (6-AM) were higher in the medulla than in blood. The brain: blood ratio for the analytes demonstrated an increasing ratio from morphine, to codeine, to 6-AM (1.42, 2.48 and 4.86), which corresponds to the relative lipophilicity of these analytes. The average right and left lung weights were 762 and 668 g, respectively. Histologic examination showed edema, and/or polarizable microemboli, acute bronchopneumonia and acute bronchitis. The preferential distribution of opiates to medulla suggests that lingering opiate deaths may be explained, at least in part, because of higher relative concentrations of drug in brain, compared with femoral blood.

Metabolic phenotype of rats exposed to heroin and potential markers of heroin abuse

BACKGROUND

Metabolomics allows the high-throughput analysis of low molecular mass compounds in biofluids, which can reflect the metabolic response of the body to heroin exposure and potentially reveal biomarkers of heroin abuse.

METHODS

Heroin was administered to Sprague-Dawley rats in increasing doses from 3 to 16.5 mg kg(-1)d(-1) (i.p.) for 10 days, then withdrawn and re-administered for 4 days. The analytes in serum and urine were profiled using gas chromatography-mass spectrometry, and metabolic patterns were evaluated based on the metabolomics data.

RESULTS

Both the administration and withdrawal of heroin resulted in aberrant behaviour in the rats; however, the rats gradually became adapted to heroin. Metabolomics data showed that heroin administration caused deviations in the metabolic patterns, whereas heroin withdrawal restored the metabolic patterns towards baseline. Re-administration of heroin caused the metabolic patterns to deviate again. Analysis of the metabolites revealed that heroin induced an acceleration of the tricarboxylic acid cycle and the metabolism of free fatty acids that may contribute to the reduction in observed body weight in the heroin group. Heroin administration decreased tryptophan and 5-hydroxytryptamine levels in peripheral serum but increased urinary tryptophan and 5-hydroxyindoleacetate. Withdrawal of heroin for 4 days efficiently restored all metabolites to baseline, except serum myo-inositol-1-phosphate, threonate, and hydroxyproline in the urine.

CONCLUSIONS

Heroin administration significantly perturbed metabolic pathways, elevated energy metabolism, whereas heroin withdrawal restored all but a few metabolites to baseline. These peripheral metabolites were indicated as the surrogates characterising the metabolic effect of heroin on central nervous system function.

Feasibility of double-blind clinical trials with oral diacetylmorphine: a randomized controlled phase II study in an inpatient setting

The aim of this study was to evaluate the feasibility of conducting double-blind controlled randomized clinical trials using twice-a-day immediate-release oral diacetylmorphine (DAM) in heroin-dependent patients, by means of measuring the capacity of oral DAM to block opiate withdrawal and clinicians' ability to distinguish it from morphine and methadone. This was a randomized, phase II, double-blind, multicenter pilot study comparing immediate-release oral DAM, slow-release oral morphine and oral methadone administered twice a day during 10 days. Forty-five heroin-dependent patients were randomly assigned to these three treatment groups in an inpatient regime. Patients were stabilized with a mean of 350 mg (SD = 193) of immediate-release oral DAM, 108 mg (SD = 46.2) of slow-release oral morphine and 40 mg (SD = 17.9) of methadone. No statistically significant differences were found between any studied medication in clinical outcome. Neither patients nor clinicians were able to identify the administered medication. This study shows the feasibility of double-blind clinical trials using b.i.d. immediate-release oral DAM allowing further phase III clinical trials in the process of introducing oral DAM as a medication for heroin-dependent patients not responding to standard maintenance treatments.

The effect of temperature and pH on the deacetylation of diamorphine in aqueous solution and in human plasma

The effect of temperature on the kinetics of the deacetylation of diamorphine and 6-monoacetylmorphine was studied in human plasma. Diamorphine was rapidly and quantitatively degraded to 6-monoacetylmorphine with initial half-lives of 354, 18 and 3 min at temperatures of 4, 25 and 37°C, respectively. Further deacetylation to morphine was not detected. In aqueous solution, diamorphine was quantitatively degraded to give 6-monoacetylmorphine as the major product and morphine as a minor product, the rate of deacetylation being dependent on temperature and pH. At pH 4·0 and 5·6 diamorphine had a half-life of greater than 14 days at all temperatures but at alkaline pH diamorphine was rapidly deacetylated. The rate of deacetylation of 6-monoacetylmorphine was consistently slower than that of diamorphine under identical conditions of pH and temperature. A method is described for the rapid stabilization and subsequent assay of diamorphine in plasma which will prevent errors in estimation of the drug due to unwanted hydrolysis.

Temporal changes of smoking status and motivation among Chinese heroin-dependent, methadone-maintained smokers

INTRODUCTION

The rates of cigarette smoking remain extremely high in active heroin users and methadone-maintained patients. It remains undetermined whether smoking status and motivation would be differentially affected by heroin and methadone administration.

METHODS

Heroin-dependent, methadone-maintained patients were recruited in the present studies. A battery of self-report questionnaires was used in the current study, in order to assess smoking status and motivations before first heroin use, during active heroin use and after Methadone Maintenance Treatment (MMT) admission.

RESULTS

An extremely high portion of participants started smoking before first heroin use. The highest level of cigarette smoking was found during the period of active heroin use, and cigarette consumption was reported to decrease after MMT admission. A wide range of smoking motivations were found before first heroin use. Moreover, "maintaining heroin pleasure" was the primary motivation for the increase in cigarette consumption during the period of active heroin use and 1h after heroin administration, while "habitual smoking" was the primary smoking motivation before first heroin use and after MMT admission respectively.

CONCLUSIONS

The present study first demonstrated that the prolonged rewarding effect of heroin following cigarette smoking may account for the increase of nicotine consumption found in the heroin-dependent patients. It appears that heroin and methadone differentially influenced smoking status and motivation among heroin-dependent, methadone-maintained patients.

Pharmacotherapy in the treatment of addiction: methadone

Methadone maintenance treatment (MMT) is the most widely available pharmacotherapy for opioid addiction and has been shown to be an effective and safe treatment over a period of 40 years. Although women comprise approximately 40% of clients currently being treated in MMT programs, comparatively little research geared specifically toward this group has been published. This article begins with an overview of neurobiological studies on opioid addiction, including a discussion of gender differences, followed by a review of the pharmacology of methadone. The authors then examine the particular needs and differences of women being treated in MMTs, including co-dependence with other substances, women's health issues, and psychosocial needs unique to this population. Research shows that women have different substance abuse treatment needs in comparison to their male counterparts. One New York City MMT program that has attempted to address these differences is highlighted.

Heroin-assisted treatment in the Netherlands: History, findings, and international context

This monograph describes the history, findings and international context of heroin-assisted treatment (HAT) in the Netherlands. The monograph consists of (1) a short introduction and seven paragraphs describing the following aspects of HAT in the Netherlands: (2) history of HAT studies and implementation of routine HAT in the Netherlands; (3) main findings on efficacy, safety and cost-effectiveness from the two randomized controlled HAT trials in the Netherlands; (4) new findings from a large cohort study on the effectiveness of HAT in routine clinical practice in the Netherlands; (5) unique data on the patient's perspective of HAT; (6) data on the pharmacological and pharmaceutical basis for HAT in the Netherlands; (7) description of the registration process; and (8) account of the international context of HAT. Together, these data show that HAT can now be considered a safe and proven-effective intervention for the treatment of chronic, treatment-resistant heroin dependent patients.

Increased locomotor activity induced by heroin in mice: pharmacokinetic demonstration of heroin acting as a prodrug for the mediator 6-monoacetylmorphine in vivo

We investigated the relative importance of heroin and its metabolites in eliciting a behavioral response in mice by studying the relationship between concentrations of heroin, 6-monoacetylmorphine (6MAM), and morphine in brain tissue and the effects on locomotor activity. Low doses (subcutaneous) of heroin (< or =5 micromol/kg) or 6MAM (< or =15 micromol/kg) made the mice run significantly more than mice given equimolar doses of morphine. There were no differences in the response between heroin and 6MAM, although we observed a shift to the left of the dose-response curve for the maximal response of heroin. The behavioral responses were abolished by pretreatment with 1 mg/kg naltrexone. Heroin was detected in brain tissue after injection, but the levels were low and its presence too short-lived to be responsible for the behavioral response observed. The concentration of 6MAM in brain tissue increased shortly after administration of both heroin and 6MAM and the concentration changes during the first hour roughly reflected the changes in locomotor activity. Both the maximal and the total concentration of 6MAM were higher after administration of heroin than after administration of 6MAM itself. The morphine concentration increased slowly after injection and could not explain the immediate behavioral response. In summary, the locomotor activity response after injection of heroin was mediated by 6MAM, which increased shortly after administration. Heroin acted as an effective prodrug. The concentration of morphine was too low to stimulate the immediate response observed but might have an effect on the later part of the heroin-induced behavioral response curve.

Prescription of heroin for the management of heroin dependence: current status

The prescription of heroin (diamorphine) for the management of heroin dependence is a controversial treatment approach that was limited to Britain until the 1990s. Since then a number of countries have embarked upon clinical trials of this approach, and it is currently licensed and available in several European countries. To date, six randomized controlled trials (RCTs) with over 1600 patients and several cohort studies have examined injected (or inhaled) heroin treatment. This article reviews relevant clinical pharmacology, how heroin treatment programmes are delivered, and the evidence regarding safety, efficacy and cost-effectiveness from RCTs. Heroin is usually prescribed in intravenous dosages of 300-500 mg/day, divided in two or three doses. Uncommon but serious side effects include seizures and respiratory depression immediately following injection. Despite methodological shortcomings, RCTs generally indicate that heroin treatment results in a comparable retention, improved general health and psychosocial functioning, and less self-reported illicit heroin use than oral methadone treatment. Cost-effectiveness studies indicate heroin treatment to be more expensive to deliver but to result in savings in the criminal justice sector. There has been debate regarding how heroin treatment should be positioned within the range of treatment approaches for this condition. There is increasing consensus that, in countries that have robust and accessible treatment systems for heroin users, heroin treatment is suited to a minority of heroin users as a second-line treatment for those individuals who do not respond to methadone or buprenorphine treatment delivered under optimal conditions.

Route of drug use and its implications for drug effect, risk of dependence and health consequences

Route of administration has a profound, but often overlooked, influence on the actual experience of the drug use itself, on the risk of resulting development of dependence, and on the nature of the harms to which drug users are exposing themselves. These three areas are reviewed. The influence of route of administration on drug effect is considered first with regard to overall effectiveness of absorption, and also with regard to speed of onset of effect. The implications for risk of dependence cover animal and human laboratory studies of reinforcement schedules, epidemiological studies, the attitudes of drug users themselves to the different routes of possible drug use and associated dependence risk and the postulated influences on progression to dependence. Finally, the relationship between route of drug use and health sequelae is explored for the three most widely used routes of administration of illicit drugs-snorting, smoking and injecting.

Oral diacetylmorphine (heroin) yields greater morphine bioavailability than oral morphine: bioavailability related to dosage and prior opioid exposure

AIMS

In the Swiss heroin substitution trials, patients are treated with self-administered diacetylmorphine (heroin). Intravenous administration is not possible in patients that have venosclerosis. Earlier studies have demonstrated that oral diacetylmorphine may be used, although it is completely converted to morphine presystemically. Morphine bioavailability after high-dose oral diacetylmorphine is considerably higher than would be predicted from low-dose trials. The aim was to investigate whether the unexpectedly high bioavailability is due to a difference in the drug examined, and whether it depends on previous exposure or on dose.

METHODS

Opioid-naive healthy volunteers and dependent patients from the Swiss heroin trials (n = 8 per group) received low doses of intravenous and oral deuterium-labelled morphine and diacetylmorphine, respectively. Patients also received a high oral diacetylmorphine dose.

RESULTS

The maximum plasma concentration (C(max)) of morphine was twofold higher after oral diacetylmorphine than after morphine administration in both groups. However, morphine bioavailability was considerably higher in chronic users [diacetylmorphine 45.6% (95% confidence interval 40.0, 51.3), morphine 37.2% (30.1, 44.3)] than in naive subjects [diacetylmorphine 22.9% (16.4, 29.4), morphine 23.9% (16.5, 31.2)] after low oral doses (48.5 micromol) of either diacetylmorphine or morphine. Morphine clearance was similar in both groups. Moreover, oral absorption of morphine from diacetylmorphine was found to be dose dependent, with bioavailability reaching 64.2% (55.3, 73.1) for high diacetylmorphine doses (1601 micromol).

CONCLUSIONS

Oral absorption of opioids is substance-, dose- and patient collective-dependent, suggesting that there may be a saturation of first-pass processes, the exact mechanism of which is not yet understood.

The runway model of drug self-administration

Behavioral scientists have employed operant runways as a means of investigating the motivational impact of incentive stimuli for the better part of the past 100 years. In this task, the speed with which a trained animal traverses a long straight alley for positive incentive stimuli, like food or water, provides a reliable index of the subject's motivation to seek those stimuli. The runway is therefore a particularly appropriate tool for investigating the drug-seeking behavior of animals working for drugs of abuse. The current review describes our laboratory's work over the past twenty years developing and implementing an operant runway model of drug self-administration. Procedures are described that methodologically dissociate the antecedent motivational processes that induce an animal to seek a drug, from the positive reinforcing consequences of actually earning the drug. Additional work is reviewed on the use of the runway method as a means of modeling the factors that often result in a "relapse" of drug self-administration after a period of abstinence (i.e., a response reinstatement test), as are runway studies that revealed the presence of opposing positive and negative consequences of self-administered cocaine. This body of work suggests that the runway method has served as a powerful behavioral tool for the study of the behavioral and neurobiological basis of drug self-administration.

Intranasal naloxone for the treatment of suspected heroin overdose

AIMS

This paper reviews available literature regarding the effectiveness, safety and utility of intranasal (i.n.) naloxone for the treatment of heroin overdose.

METHODS

Scientific literature in the form of published articles during the period January 1984 to August 2007 were identified by searching several databases including Medline, Cinahl and Embase for the following terms: naloxone, narcan, intranasal, nose. The data extracted included study design, patient selection, numbers, outcomes and adverse events.

RESULTS

Reports of the pharmacological investigation and administration of i.n. naloxone for heroin overdose are included in this review. Treatment of heroin overdose by administration of i.n. naloxone has been introduced as first-line treatment in some jurisdictions in North America, and is currently under investigation in Australia.

CONCLUSION

Currently there is not enough evidence to support i.n. naloxone as first-line intervention by paramedics for treatment of heroin overdose in the pre-hospital setting. Further research is required to confirm its clinical effectiveness, safety and utility. If proved effective, the i.n. route may be useful for drug administration in community settings (including peer-based administration), as it reduces risk of needlestick injury in a population at higher risk of blood-borne viruses. Problematically, naloxone is not manufactured currently in an ideal form for i.n. administration.

A five-year review of the medical outcome of heroin body stuffers

The medical outcome of heroin body stuffers has rarely been described. This study was performed to illustrate the clinical course of heroin body stuffers. A retrospective chart analysis was performed on all cases of heroin body stuffers received by a metropolitan poison control center from 2000-2004. We identified 65 heroin body stuffers. Sixty-nine percent were men with a mean age of 35 years. The stated quantity of heroin containers ingested ranged from 1 to 30, with 65% reported as being wrapped in plastic. Six patients (9.2%) developed symptoms of opiate intoxication. All symptoms began within an hour after the ingestion. Three patients (4.6%) needed naloxone. The mean length of observation was 24 h. Opiate intoxication from heroin stuffing is uncommon. Those patients that developed symptoms did so early in their course. These data indicate a benign clinical course in most heroin body stuffers.

Morphine and heroin differentially modulate in vivo hippocampal LTP in opiate-dependent rat

Addictive drugs have been shown to severely influence many neuronal functions, which are considered as the underlying mechanisms for physiological and psychological dependences. We previously showed that in vivo LTP in rat hippocampal CA1 region is significantly reduced during withdrawal following chronic opiates treatment, and the reduced LTP can be restored by re-exposure of animals to corresponding drugs. Here, we further demonstrated that during opiates withdrawal, the re-exposure of morphine either systemically (subcutaneously) or locally (intracerebroventricularly) could restore the reduced LTP in heroin-dependent rats, but heroin could not restore the reduced LTP, in morphine-dependent rats, indicating differential modulations of hippocampal functions by those two opiates. In contrast, DAMGO, a mu-opioid receptor (MOR) agonist, could restore the reduced LTP, and CTOP, a MOR antagonist, could block the restoration in rats dependent on both opiates, showing that MOR is functional under such conditions. However, the upregulation of hippocampal PKA activity during morphine withdrawal could be suppressed by re-exposure of morphine but not that of heroin, suggesting a likely underlying mechanism of the differential modulation of LTP by two opiates. Taken together, our study clearly demonstrates that chronic abuse of opiates inevitably leads to severe alteration of hippocampal LTP, and reveals the interesting differences between morphine and heroin in their effects on the differential modulation of hippocampal synaptic plasticity.

Concentrations of scheduled prescription drugs in blood of impaired drivers: considerations for interpreting the results

We report the concentrations of scheduled prescription drugs in blood samples from people arrested in Sweden for driving under the influence of drugs (DUID). The investigation covered a 2 year period 2004 (N = 7052 cases) and 2005 (N = 7759 cases) and was prompted by recent legislation stipulating zero-concentration limits in blood for controlled substances. However, prescription drugs are exempt from the zero-limit law provided that the medication was being used in accordance with a doctor's prescription. The blood concentrations of various psychoactive substances were compared with the limits of quantitation of the analytic method used and the so-called therapeutic concentration range according to various reference books and tabulations. Diazepam [N = 1950 (26%)] and nordazepam [N = 2168 (28%)] were the therapeutic agents most frequently identified in these forensic blood samples along with other benzodiazepines such as alprazolam [N = 430 (5.6%)], flunitrazepam [N = 308 (4.0%)], and nitrazepam [N = 222 (2.9%)]. The newer hypnotics, exemplified by zolpidem [N = 148 (1.9%)] and zopiclone [N = 111 (1.5%)], were also high on the list of psychoactive substances identified. Interpreting the concentration of a prescription drug in blood in relation to whether the person had taken an overdose or was abusing the substance in question is not always easy. The age, gender, degree of obesity, and ethnicity of the person concerned; the pharmacokinetic profile of the drug; polymorphism of drug-metabolizing enzymes as well as liver and kidney function and blood hematocrit need to be considered. Among preanalytic factors, stability of the drug in blood after sampling, the type of tubes and preservatives used, the dosage form and route of administration deserve consideration. When therapeutic drug monitoring concentrations are compared with forensic toxicology results, then the plasma-to-whole blood distribution ratio of the drug also needs to be considered. In blood samples from DUID suspects, the concentrations of many commonly used sedatives and hypnotics exceeded the accepted therapeutic limits, which gives an indication of the abuse potential of these types of medications.

Pharmacokinetics and pharmacodynamics of high doses of pharmaceutically prepared heroin, by intravenous or by inhalation route in opioid-dependent patients

A pharmacokinetic-pharmacodynamic study was performed in opioid-dependent patients in the Netherlands, who were currently treated with high doses of pharmaceutically prepared heroin on medical prescription. Besides intravenous heroin, heroin was prescribed for inhalation by "chasing the dragon" method. In this technique, heroin base is heated on aluminium foil, and heroin vapours are inhaled into the lungs. Not much is known about the pharmacokinetics profile and bioavailability of this specific administration method. Therefore, a study was performed on pharmacokinetics and pharmacodynamics of heroin inhalation and intravenous use. Eleven patients who injected heroin and 9 patients who inhaled heroin entered the study. They were on steady-state heroin treatment for at least 12 months. For safety reasons, there was no crossing-over between heroin injection or inhalation. In a double-blind randomised study, 67-100-150% of the regular heroin maintenance dose was administered to each patient. Maximal single heroin dose was 450 mg. Plasma concentrations of heroin and its metabolites 6-monoacetylmorphine, morphine and morphine-glucuronides were analysed using LC-MS-MS. Blood pressure, heart rate, skin temperature and reaction time were assessed. Furthermore, visual analogue scales regarding craving and appreciation of heroin effect were scored by the subjects. Both in inhaling and injecting patients, the areas under curve of heroin and all measured metabolites were linearly related to heroin dose. Mean C(max) of heroin and its metabolites were 2-6 times lower after inhalation, than after intravenous injection. Bioavailability (F) of heroin inhalation was estimated as 52% (95% CI 44-61%). Heroin was rapidly cleared from plasma. Cl/F was 930 l/hr (95% CI 799-1061 l/hr) after intravenous administration, and 1939 l/hr (95% CI 1661-2217 l/hr) after inhalation. Heroin Cl and Vd were correlated to body weight (R(2) 15-19%). Morphine-glucuronides levels were inversely related to creatinine clearance. After heroin administration, the reaction time was significantly prolonged with 28+/-5.3 msec. in injecting and 13+/-4.9 msec. in inhaling patients. Cardiovascular changes were only mild after heroin administration. Craving-scores declined immediately after heroin administration in both administration groups. Subjective heroin effect was rated more positively in heroin inhaling than in injecting patients, despite the lower C(max) levels following heroin inhalation. In both groups, in this blinded study heroin dose increments were more appreciated than dose reductions. Increments of 50% of the regular heroin dose did not cause any serious side effect.

Morphine withdrawal dramatically reduces lymphocytes in morphine-dependent macaques

The immune effects of chronic opiate exposure and/or opiate withdrawal are not well understood. The results of human studies with opiate abusers are variable and may not be able to control for important factors such as subjects' drug histories, health and nutritional status. Nonhuman primate models are necessary to control these important factors. A model of opiate dependence in macaques was developed to study the effects of opiate dependence and withdrawal on measures of immune function. Four pigtailed macaques drank a mixture of morphine (20 mg/kg/session) and orange-flavored drink every 6 h for several months. During stable morphine dependence, absolute numbers of neutrophils, monocytes and lymphocytes did not change relative to pre-morphine levels. However, there was a significant decrease in the absolute number and percentage of natural killer (NK) cells in morphine dependence. Either precipitated withdrawal or abstinence for 24 h resulted in behavioral withdrawal signs in all animals. Absolute lymphocyte counts decreased and absolute netrophil counts increased significantly in withdrawal, relative to levels during morphine dependence. Lymphocyte subset (CD4+, CD8+, CD20+) cells were also decreased in absolute numbers with little change in their percentage distributions. There was, however, a significant increase in the percentage of NK cells in withdrawal relative to levels during morphine dependence. This study demonstrates the usefulness of voluntary oral self-dosing procedures for maintaining morphine dependence in nonhuman primates and demonstrates that the morphine withdrawal syndrome includes large alterations in blood parameters of immune system function, including nearly 50% reduction in numbers of CD4+, CD8+ and CD20+ cells.