Alpha2 adrenergic agonists for the management of opioid withdrawal

An ensemble recruited by α2a-adrenergic receptors is engaged in a stressor-specific manner in mice

α2a-adrenergic receptor (α2a-AR) agonists are candidate substance use disorder therapeutics due to their ability to recruit noradrenergic autoreceptors to dampen stress system engagement. However, we recently found that postsynaptic α2a-ARs are required for stress-induced reinstatement of cocaine-conditioned behavior. Understanding the ensembles recruited by these postsynaptic receptors (heteroceptors) is necessary to understand noradrenergic circuit control. We utilized a variety of approaches in FosTRAP (Targeted Recombination in Active Populations) mice to define an ensemble of cells activated by the α2a-AR partial agonist guanfacine ("Guansembles") in the bed nucleus of the stria terminalis (BST/BNST), a region key to stress-induced reinstatement of drug seeking. We define BNST "Guansembles" and show they differ from restraint stress-activated cells. Guanfacine produced inhibition of cAMP-dependent signaling in Guansembles, while chronic restraint stress increased cAMP-dependent signaling. Guanfacine both excited and inhibited aspects of Guansemble neuronal activity. Further, while some stressors produced overall reductions in Guansemble activity, active coping events during restraint stress and exposure to unexpected shocks were both associated with Guansemble recruitment. Using viral tracing, we define a BNST Guansemble afferent network that includes regions involved in the interplay of stress and homeostatic functions. Finally, we show that activation of Guansembles produces alterations in behavior on the elevated plus maze consistent with task-specific anxiety-like behavior. Overall, we define a population of BNST neurons recruited by α2a-AR signaling that opposes the behavioral action of canonical autoreceptor α2a-AR populations and which are differentially recruited by distinct stressors. Moreover, we demonstrate stressor-specific physiological responses in a specific neuronal population.

Intrathecal Clonidine Pump Failure Causing Acute Withdrawal Syndrome With 'Stress-Induced' Cardiomyopathy

Clonidine is a central alpha(2)-agonist antihypertensive used widely for opioid/alcohol withdrawal, attention deficit hyperactivity disorder and chronic pain management. We describe a case of clonidine withdrawal causing life-threatening hypertensive crisis and stress-induced cardiomyopathy. A 47-year-old man with chronic back pain, treated with clonidine for many years via intrathecal pump (550 mcg/24 h), presented following a collapse and complaining of sudden worsening of back pain, severe headache, diaphoresis, nausea and vomiting. A few hours prior to presentation, his subcutaneous pump malfunctioned. On presentation, vital signs included pulse 100 bpm, BP 176/103 mmHg, temperature 37.8 °C and O2 saturation 100 % (room air). Acute clonidine withdrawal with hypertensive crisis was suspected. Intravenous clonidine loading dose and a 50 mcg/h infusion were commenced. Five hours later, severe chest pain, dyspnoea, tachycardia, hypoxia, with BP 180/120 mmHg and pulmonary edema ensued. ECG showed sinus tachycardia with no ST elevation. Repeated intravenous clonidine doses were given (25 mcg every 5-10 min), with ongoing clonidine infusion to control blood pressure. Glyceryl trinitrate infusion, positive pressure ventilation and intravenous benzodiazepines were added. Bedside echocardiogram showed stress-induced cardiomyopathy pattern. Serum troponin-I was markedly elevated. His coronary angiography showed minor irregularities in the major vessels. Over the next 3 days in the ICU, drug infusions were weaned. Discharge was 12 days later on oral clonidine, metoprolol, perindopril, aspirin and oxycodone-SR. Two months later, his echocardiogram was normal. The intrathecal pump was removed. We report a case of stress-induced cardiomyopathy resulting from the sudden cessation of long-term intrathecal clonidine. This was managed by re-institution of clonidine and targeted organ-specific therapies.

Combined Interactions with I1-, I2-Imidazoline Binding Sites and α2-Adrenoceptors To Manage Opioid Addiction

Tolerance and dependence associated with chronic opioid exposure result from molecular, cellular, and neural network adaptations. Such adaptations concern opioid and nonopioid systems, including α2-adrenoceptors (α2-ARs) and I1- and I2-imidazoline binding sites (IBS). Agmatine, one of the hypothesized endogenous ligands of IBS, targeting several systems including α2-ARs and IBS, proved to be able to regulate opioid-induced analgesia and to attenuate the development of tolerance and dependence. Interested in the complex pharmacological profile of agmatine and considering the nature of its targets, we evaluated two series of imidazolines, rationally designed to simultaneously interact with I1-/I2-IBS or I1-/I2-IBS/α2-ARs. The compounds showing the highest affinities for I1-/I2-IBS or I1-/I2-IBS/α2-ARs have been selected for their in vivo evaluation on opiate withdrawal syndrome. Interestingly, 9, displaying I1-/I2-IBS/α2-ARs interaction profile, appears more effective in reducing expression and acquisition of morphine dependence and, therefore, might be considered a promising tool in managing opioid addiction.

Comparison of clonidine and dexmedetomidine for short-term sedation of intensive care unit patients

BACKGROUND AND OBJECTIVES

Patients on mechanical ventilation in intensive care unit (ICU) are often uncomfortable because of anxiety, pain, and endotracheal intubation; therefore, require sedation. Alpha-2 agonists are known to produce sedation. We compared clonidine and dexmedetomidine as sole agents for sedation.

STUDY DESIGN

Prospective, randomized, controlled open-label study.

MATERIALS AND METHODS

A total of 70 patients requiring a minimum of 12 h of mechanical ventilation with concomitant sedation, were randomly allocated into two groups. Group C (n = 35) received intravenous (IV) clonidine (1 μg/kg/h titrated up to 2 μg/kg/h to attain target sedation), and Group D (n = 35) received IV dexmedetomidine for sedation (loading 0.7 μg/kg and maintenance 0.2 μg/kg/h titrated up to 0.7 μg/kg/h to achieve target sedation). A Ramsay Sedation Score of 3-4 was considered as target sedation. Additional sedation with diazepam was given when required to achieve target sedation. The quality of sedation, hemodynamic changes and adverse effects were noted and compared between the two groups.

RESULTS

Target sedation was achieved in 86% observations in Group D and 62% in Group C (P = 0.04). Additional sedation was needed by more patients in Group C compared with Group D (14 and 8 in Groups C and D, respectively, P = 0.034), mainly due to concomitant hypotension on increasing the dose of clonidine. Hypotension was the most common side-effect in Group C, occurring in 11/35 patients of Group C and 3/35 patients of Group D (P = 0.02). Rebound hypertension was seen in four patients receiving clonidine, but none in receiving dexmedetomidine.

CONCLUSION

Both clonidine and dexmedetomidine produced effective sedation; however, the hemodynamic stability provided by dexmedetomidine gives it an edge over clonidine for short-term sedation of ICU patients.

Cannabinoid and opioid interactions: implications for opiate dependence and withdrawal

Withdrawal from opiates, such as heroin or oral narcotics, is characterized by a host of aversive physical and emotional symptoms. High rates of relapse and limited treatment success rates for opiate addiction have prompted a search for new approaches. For many opiate addicts, achieving abstinence may be further complicated by poly-drug use and co-morbid mental disorders. Research over the past decade has shed light on the influence of endocannabinoids (ECs) on the opioid system. Evidence from both animal and clinical studies point toward an interaction between these two systems, and suggest that targeting the EC system may provide novel interventions for managing opiate dependence and withdrawal. This review will summarize the literature surrounding the molecular effects of cannabinoids and opioids on the locus coeruleus-norepinephrine system, a key circuit implicated in the negative sequelae of opiate addiction. A consideration of the trends and effects of marijuana use in those seeking treatment to abstain from opiates in the clinical setting will also be presented. In summary, the present review details how cannabinoid-opioid interactions may inform novel interventions in the management of opiate dependence and withdrawal.

The insula and drug addiction: an interoceptive view of pleasure, urges, and decision-making

We have recently shown that damage to the insula leads to a profound disruption of addiction to cigarette smoking (Naqvi et al., Science 315:531-534, 2007). Yet, there is little understanding of why the insula should play such an important role in an addictive behavior. A broad literature (much of it reviewed in this issue) has addressed the role of the insula in processes related to conscious interoception, emotional experience, and decision-making. Here, we review evidence for the role of the insula in drug addiction, and propose a novel theoretical framework for addiction in which the insula represents the interoceptive effects of drug taking, making this information available to conscious awareness, memory and executive functions. A central theme of this framework is that a primary goal for the addicted individual is to obtain the effects of the drug use ritual upon the body, and representations of this goal in interoceptive terms by the insula contribute to how addicted individuals feel, remember, and decide about taking drugs. This makes drug addiction like naturally motivated behaviors, such as eating and sex, for which an embodied ritual is the primary goal.

Opioid dependence treatment: options in pharmacotherapy

The development of effective treatments for opioid dependence is of great importance given the devastating consequences of the disease. Pharmacotherapies for opioid addiction include opioid agonists, partial agonists, opioid antagonists, and alpha-2-adrenergic agonists, which are targeted toward either detoxification or long-term agonist maintenance. Agonist maintenance therapy is currently the recommended treatment for opioid dependence due to its superior outcomes relative to detoxification. Detoxification protocols have limited long-term efficacy, and patient discomfort remains a significant therapy challenge. Buprenorphine's effectiveness relative to methadone remains a controversy and may be most appropriate for patients in need of low doses of agonist treatment. Buprenorphine appears superior to alpha-2 agonists, however, and office-based treatment with buprenorphine in the USA is gaining support. Studies of sustained-release formulations of naltrexone suggest improved effectiveness for retention and sustained abstinence; however, randomized clinical trials are needed.

Intermittent marijuana use is associated with improved retention in naltrexone treatment for opiate-dependence

Naltrexone is a theoretically promising alternative to agonist substitution treatment for opioid dependence, but its effectiveness has been severely limited by poor adherence. This study examined, in an independent sample, a previously observed association between moderate cannabis use and improved retention in naltrexone treatment. Opioid dependent patients (N = 63), admitted for inpatient detoxification and induction onto oral naltrexone, and randomized into a six-month trial of intensive behavioral therapy (Behavioral Naltrexone Therapy) versus a control behavioral therapy (Compliance Enhancement), were classified into three levels of cannabis use during treatment based on biweekly urine toxicology: abstinent (0% cannabis positive urine samples); intermittent use (1% to 79% cannabis positive samples); and consistent use (80% or greater cannabis positive samples). Intermittent cannabis users showed superior retention in naltrexone treatment (median days retained = 133; mean = 112.8, SE = 17.5), compared to abstinent (median = 35; mean = 47.3, SE = 9.2) or consistent users (median = 35; mean = 68.3, SE = 14.1) (log rank = 12.2, df = 2, p = .002). The effect remained significant in a Cox model after adjustment for baseline level of heroin use and during treatment level of cocaine use. Intermittent cannabis use was also associated with greater adherence to naltrexone pill-taking. Treatment interacted with cannabis use level, such that intensive behavioral therapy appeared to moderate the adverse prognosis in the consistent cannabis use group. The association between moderate cannabis use and improved retention on naltrexone treatment was replicated. Experimental studies are needed to directly test the hypothesis that cannabinoid agonists exert a beneficial pharmacological effect on naltrexone maintenance and to understand the mechanism.

Electrocardiographic effects of lofexidine and methadone coadministration: secondary findings from a safety study

STUDY OBJECTIVE

To determine the electrocardiographic effects of coadministration of lofexidine and methadone.

DESIGN

Prospective, double-blind study.

SETTING

Outpatient drug treatment research clinic.

PARTICIPANTS

Fourteen adults (mean +/- SD age 34.9 +/- 5.3 yrs) with physical dependence on opioids.

INTERVENTION

Participants were stabilized on methadone maintenance therapy, reaching a target dose of 80 mg/day. After 3 weeks of methadone stabilization, participants received lofexidine 0.4 mg or placebo once/day, each for 1 week, administered at the same time as methadone. From weeks 3-8, all subjects received lofexidine, with the dose escalated each week in 0.2-mg increments so that by week 8, participants were receiving lofexidine 1.6 mg/day. Electrocardiograms (ECGs) were obtained at baseline (before methadone), after stabilization with methadone, and after lofexidine coadministration during peak plasma lofexidine levels.

MEASUREMENTS AND MAIN RESULTS

Prespecified outcome measures of mean and maximal changes in heart rate, and PR, QRS, and QTc intervals were obtained after stabilization with methadone and after lofexidine 0.4 mg coadministration. Repeated-measures regression showed no significant changes in heart rate or PR, QRS, or QTc interval after methadone stabilization, but a significant decrease in heart rate (mean +/- SD -8.0 +/- 7.3 beats/min, p=0.0006) after starting lofexidine. When data were analyzed by using maximal ECG response, again, no significant changes were noted during methadone induction compared with baseline, but significant changes did occur in all four ECG parameters when lofexidine was coadministered: decreased heart rate (mean +/- SD -9.6 +/- 5.8 beats/min, p<0.0001) and increased PR interval (+11.1 +/- 19.8 msec, p=0.026), QRS interval (+3.7 +/- 4.3 msec, p=0.002), and QTc interval (+21.9 +/- 40.8 msec, p=0.018). In three female participants, the change in QTc interval from baseline was clinically significant (> 40 msec).

CONCLUSION

Our preliminary data suggest that coadministration of lofexidine and methadone induces QTc interval prolongation. This drug combination should be prescribed cautiously, with ECG monitoring. Furthermore, because the participants with the largest changes in QTc interval in our study were female, women may be at highest risk.

Carbon Nanotube Membranes for use in the Transdermal Treatment of Nicotine Addiction and Opioid Withdrawal Symptoms

Transdermal systems are attractive methods of drug administration specifically when treating patients for drug addiction. Current systems however are deficient in therapies that allow variable flux values of drug, such as nicotine for smoking cessation or complex dosing regimens using clonidine when treating opioid withdrawal symptoms. Through the use of functionalized carbon nanotube (CNT) membranes, drug delivery to the skin can be controlled by applying a small electrical bias to create a programmable drug delivery system. Clearly, a transdermal patch system that can be tailored to an individual’s needs will increase patient compliance as well as provide much more efficient therapy. The purpose of this paper is to discuss the applicability of using carbon nanotube membranes in transdermal systems for treatment of drug abuse.

A Phase 3 placebo-controlled, double-blind, multi-site trial of the alpha-2-adrenergic agonist, lofexidine, for opioid withdrawal

CONTEXT

Lofexidine is an alpha-2-adrenergic receptor agonist that is approved in the United Kingdom for the treatment of opioid withdrawal symptoms. Lofexidine has been reported to have more significant effects on decreasing opioid withdrawal symptoms with less hypotension than clonidine.

OBJECTIVE

To demonstrate that lofexidine is well tolerated and effective in the alleviation of observationally defined opioid withdrawal symptoms in opioid dependent individuals undergoing medically supervised opioid detoxification as compared to placebo.

DESIGN

An inpatient, Phase 3, placebo-controlled, double-blind, randomized multi-site trial with three phases: (1) opioid agonist stabilization phase (days 1-3), (2) detoxification/medication or placebo phase (days 4-8), and (3) post detoxification/medication phase (days 9-11).

SUBJECTS

Sixty-eight opioid dependent subjects were enrolled at three sites with 35 randomized to lofexidine and 33 to placebo.

MAIN OUTCOME MEASURE

Modified Himmelsbach Opiate Withdrawal Scale (MHOWS) on study day 5 (second opioid detoxification treatment day).

RESULTS

Due to significant findings, the study was terminated early. On the study day 5 MHOWS, subjects treated with lofexidine had significantly lower scores (equating to fewer/less severe withdrawal symptoms) than placebo subjects (least squares means 19.5+/-2.1 versus 30.9+/-2.7; p=0.0019). Lofexidine subjects had significantly better retention in treatment than placebo subjects (38.2% versus 15.2%; Log rank test p=0.01).

CONCLUSIONS

Lofexidine is well tolerated and more efficacious than placebo for reducing opioid withdrawal symptoms in inpatients undergoing medically supervised opioid detoxification.

The ibogaine medical subculture

AIM OF THE STUDY

Ibogaine is a naturally occurring psychoactive indole alkaloid that is used to treat substance-related disorders in a global medical subculture, and is of interest as an ethnopharmacological prototype for experimental investigation and possible rational pharmaceutical development. The subculture is also significant for risks due to the lack of clinical and pharmaceutical standards. This study describes the ibogaine medical subculture and presents quantitative data regarding treatment and the purpose for which individuals have taken ibogaine.

MATERIALS AND METHODS

All identified ibogaine "scenes" (defined as a provider in an associated setting) apart from the Bwiti religion in Africa were studied with intensive interviewing, review of the grey literature including the Internet, and the systematic collection of quantitative data.

RESULTS

Analysis of ethnographic data yielded a typology of ibogaine scenes, "medical model", "lay provider/treatment guide", "activist/self-help", and "religious/spiritual". An estimated 3414 individuals had taken ibogaine as of February 2006, a fourfold increase relative to 5 years earlier, with 68% of the total having taken it for the treatment of a substance-related disorder, and 53% specifically for opioid withdrawal.

CONCLUSIONS

Opioid withdrawal is the most common reason for which individuals took ibogaine. The focus on opioid withdrawal in the ibogaine subculture distinguishes ibogaine from other agents commonly termed "psychedelics", and is consistent with experimental research and case series evidence indicating a significant pharmacologically mediated effect of ibogaine in opioid withdrawal.

The clinical use of buprenorphine in opiate addiction: evidence and practice

Buprenorphine is a partial μ-opioid receptor agonist that is being increasingly used in clinical practice in the treatment of opioid dependence in the UK, USA, and, elsewhere. Its unique pharmacological properties mean it is a relatively safe drug, it can be given by alternate day dispensing, and it is associated with relatively mild symptoms on withdrawal. The interpretation of the research literature on buprenorphine is however, complex, and often appears to be in conflict with how buprenorphine is used in clinical practice. This article describes these apparent contradictions, their likely explanations, and how these may further inform our clinical practice. The article also describes the clinically relevant pharmacological properties of buprenorphine, compares it to methadone, relates the evidence to clinical experience, and provides practical advice on how to manage the most common clinical techniques. The best quality evidence suggests that very rapid buprenorphine induction is not associated with a higher drop-out rate than methadone, that buprenorphine is probably as good as methadone for maintenance treatment, and is superior to methadone and α-2 adrenergic agonists for detoxification. However, buprenorphine cannot yet be considered the 'gold standard' treatment for opiate dependence because of the higher drop-out rates that may occur on induction using current techniques, its high-cost relative to methadone, and because the place of buprenorphine in treatment is still continuing to evolve.