Pharmacologic management of relapse prevention in addictive disorders

Cannabinoid Antagonist Drug Discrimination in Nonhuman Primates

Despite a growing acceptance that withdrawal symptoms can emerge following discontinuation of cannabis products, especially in high-intake chronic users, there are no Food and Drug Administration (FDA)-approved treatment options. Drug development has been hampered by difficulties studying cannabis withdrawal in laboratory animals. One preclinical approach that has been effective in studying withdrawal from drugs in several pharmacological classes is antagonist drug discrimination. The present studies were designed to examine this paradigm in squirrel monkeys treated daily with the long-acting CB₁ agonist AM2389 (0.01 mg/kg) and trained to discriminate the CB₁ inverse agonist/antagonist rimonabant (0.3 mg/kg) from saline. The discriminative-stimulus effects of rimonabant were both dose and time dependent and, importantly, could be reproduced by discontinuation of agonist treatment. Antagonist substitution tests with the CB₁ neutral antagonists AM4113 (0.03-0.3 mg/kg), AM6527 (0.03-1.0 mg/kg), and AM6545 (0.03-1.0 mg/kg) confirmed that the rimonabant discriminative stimulus also could be reproduced by CB₁ antagonists lacking inverse agonist action. Agonist substitution tests with the phytocannabinoid ∆⁹-tetrahydrocannabinol (0.1-1.0 mg/kg), synthetic CB₁ agonists nabilone (0.01-0.1 mg/kg), AM4054 (0.01-0.03 mg/kg), K2/Spice compound JWH-018 (0.03-0.3 mg/kg), FAAH-selective inhibitors AM3506 (0.3-5.6 mg/kg), URB597 (3.0-5.6 mg/kg), and nonselective FAAH/MGL inhibitor AM4302 (3.0-10.0 mg/kg) revealed that only agonists with CB₁ affinity were able to reduce the rimonabant-like discriminative stimulus effects of withholding daily agonist treatment. Although the present studies did not document physiologic disturbances associated with withdrawal, the results are consistent with the view that the cannabinoid antagonist drug discrimination paradigm provides a useful screening procedure for examining the ability of candidate medications to attenuate the interoceptive stimuli provoked by cannabis discontinuation. SIGNIFICANCE STATEMENT: Despite a growing acceptance that withdrawal symptoms can emerge following the discontinuation of cannabis products, especially in high-intake chronic users, there are no FDA-approved pharmacotherapies to assist those seeking treatment. The present studies systematically examined cannabinoid antagonist drug discrimination, a preclinical animal model that is designed to appraise the ability of candidate medications to attenuate the interoceptive effects that accompany abrupt cannabis abstinence.

Prevention of homicidal behaviour in men with psychiatric disorders

OBJECTIVES

Homicide is overwhelmingly committed by men compared to women. Conservative estimates suggest that more than a third of these individuals have a treatable psychiatric disorder. These data present an opportunity to mental health clinicians to assist in the prevention of homicide by improving men's mental health.

METHODS

We review the current literature on men's mental health with a focus on assessing and reducing homicide risk in men with psychiatric conditions.

RESULTS

Bipolar disorder and schizophrenia appear to share a neural endophenotype that is a risk factor for homicide. Dual disorders, or the presence of a substance use disorder with other major mental illness, are a major risk factor for homicide in males. Dual diagnosis disorders, personality disorders and pathological traits and male depression share emotion dysregulation, irritability, and reactive aggression. Promoting physician education, addressing firearm safety, reducing the reluctance of men relative to women to engage in help-seeking behaviour, and using targeted risk interviews which integrate these data are all currently recommended.

CONCLUSIONS

The main focus in prevention of homicidal behaviour in males with psychiatric disorders should be to identify high risk groups, to provide adequate treatment, and to facilitate compliance with long-term treatment while considering male specific problems and needs.

Agonist replacement for stimulant dependence: a review of clinical research

Stimulant use disorders are an unrelenting public health concern worldwide. Agonist replacement therapy is among the most effective strategies for managing substance use disorders including nicotine and opioid dependence. The present paper reviewed clinical data from human laboratory self-administration studies and clinical trials to determine whether agonist replacement therapy is a viable strategy for managing cocaine and/or amphetamine use disorders. The extant literature suggests that agonist replacement therapy may be effective for managing stimulant use disorders, however, the clinical selection of an agonist replacement medication likely needs to be based on the pharmacological mechanism of the medication and the stimulant abused by patients. Specifically, dopamine releasers appear most effective for reducing cocaine use whereas dopamine reuptake inhibitors appear most effective for reducing amphetamine use.

Cognitive enhancement as a treatment for drug addictions

Drug addiction continues to be an important public health problem, with an estimated 22.6 million current illicit drug users in the United States alone. For many addictions, including cocaine, methamphetamine, and marijuana addiction, there are no approved pharmacological treatments. Behavioral treatments are effective but effects vary widely across individuals. Treatments that are effective across multiple addictions are greatly needed, and accumulating evidence suggests that one such approach may be pharmacological or behavioral interventions that enhance executive inhibitory control in addicts. Current evidence indicates that most forms of chronic drug use may be associated with significant cognitive impairments, especially in attention, working memory, and response inhibition functions. In some studies, these impairments predict poor treatment retention and outcome. A number of cognitive enhancing agents, including galantamine, modafinil, atomoxetine, methylphenidate, and guanfacine, have shown promising findings in human studies. Specific behavioral interventions, including cognitive remediation, also show promise. However, whether improvement of selective cognitive functions reduces drug use behavior remains to be determined. Cognitive enhancement to improve treatment outcomes is a novel strategy worthy of future research, as are related questions such as whether these approaches may be broadly beneficial to most addicts or best reserved for substance users with specific demonstrated cognitive impairments. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Agonist replacement therapy for cocaine dependence: a translational review

Cocaine use disorders are prevalent throughout the world. Agonist replacement therapy is among the most effective strategies for managing substance use disorders including nicotine and opioid dependence. This paper reviews the translational literature, including preclinical experiments, human laboratory studies and clinical trials, to determine whether agonist-replacement therapy is a viable strategy for managing cocaine dependence. Discussion is limited to transporter blockers (i.e., methylphenidate) and releasers (i.e., amphetamine analogs) that are available for use in humans in the hope of impacting clinical research and practice more quickly. The translational review suggests that agonist-replacement therapy, especially monoamine releasers, may be effective for managing cocaine dependence. Future directions for medications development are also discussed because the viability of agonist-replacement therapy for cocaine dependence may hinge on identifying novel compounds or formulations that have less abuse and diversion potential.

Subjective and physiological effects of acute intranasal methamphetamine during d-amphetamine maintenance

RATIONALE

Methamphetamine abuse and dependence are significant public-health concerns. Behavioral therapies are effective for reducing methamphetamine use. However, many patients enrolled in behavioral therapies are unable to achieve significant periods of abstinence, suggesting other strategies like pharmacotherapy are needed.

OBJECTIVES

This experiment determined the subjective and physiological effects of intranasal methamphetamine during D: -amphetamine maintenance in eight non-treatment-seeking stimulant-dependent participants. We predicted D: -amphetamine maintenance would attenuate the acute subjective effects of intranasal methamphetamine. We also predicted intranasal methamphetamine would be well tolerated during D: -amphetamine maintenance.

METHODS

After at least 7 days of maintenance on sustained-release D: -amphetamine (0 and 45 mg/day), participants were administered ascending doses of intranasal methamphetamine (0, 2.5, 5, 10, and 20 mg) across two experimental sessions. Intranasal methamphetamine doses were separated by 90 min.

RESULTS

Intranasal methamphetamine produced prototypical subjective and physiological effects (e.g., increased ratings of Like Drug; increased heart rate, blood pressure, and body temperature). The acute effects of intranasal methamphetamine were significantly diminished during D: -amphetamine maintenance relative to placebo maintenance.

CONCLUSIONS

These results are concordant with those of clinical trials and provide further support for the use of agonist replacement therapy to manage methamphetamine dependence. Additional research in humans is needed to determine the effectiveness of D: -amphetamine under different experimental conditions that more closely reflect use in the natural environment (e.g., higher methamphetamine doses) and behavioral arrangements that are predictive of pharmacotherapy effectiveness (e.g., drug self-administration).

Safety, tolerability, and feasibility of high-dose naltrexone in alcohol dependence: an open-label study

OBJECTIVE

Prior trials testing standard-dose naltrexone (50 mg/day) have generated mixed results in the treatment of alcohol dependence. The purpose of this study was to evaluate the short-term safety, tolerability, and feasibility of high-dose naltrexone (150 mg/day) for treating alcohol-dependent patients with prominent alcohol craving.

METHODS

Twenty-four alcohol-dependent outpatients received high-dose naltrexone at a dose of 150 mg/day in an 8-week open-label pilot study. All patients had current alcohol dependence and alcohol craving symptoms. Safety and tolerability were assessed weekly. Liver function tests were obtained at weeks 0, 3, 5, 7, and 9. The main outcome measures were percentage of drinking days and number of drinks per drinking day.

RESULTS

High-dose naltrexone was safe and well tolerated using the procedure described. No serious adverse effects were reported. The mean of γ-glutamyl transferase showed an improvement trend (p = 0.06), and other hepatic transaminase profiles were stable during the trial. High-dose naltrexone significantly reduced alcohol consumption (percentage of drinking days (p < 0.0001); and number of drinks per drinking day (p < 0.0001)).

CONCLUSIONS

High-dose naltrexone may serve as a viable treatment option for alcohol-dependent patients with prominent alcohol craving. Further controlled studies are needed to confirm our findings.

Environmental living conditions introduced during forced abstinence alter cocaine-seeking behavior and Fos protein expression

Environmental enrichment (EE) introduced during abstinence from cocaine self-administration is protective in reducing cue-elicited incentive motivation for cocaine in rats. This study examined neural activation associated with this protective effect of EE using Fos protein expression as a marker. Rats were trained to press a lever reinforced by cocaine (0.75 mg/kg/0.1 mL infusion) and light and tone cues across 15 consecutive days during which they were all housed in isolated conditions (IC). Rats were then assigned to either remain in IC, or to live in pair-housed conditions (PC) or EE for 30 days of forced abstinence from cocaine. Subsequently, cocaine-seeking behavior (lever presses without cocaine reinforcement) elicited by response-contingent cue presentations was assessed for 90 min, after which the rats' brains were immediately harvested for Fos protein immunohistochemistry. EE attenuated, whereas IC enhanced, cue-elicited cocaine-seeking behavior relative to PC. Also, within the prelimbic and orbitofrontal cortices and basolateral amygdala, IC enhanced, whereas EE reduced, Fos expression relative to PC. Furthermore, EE attenuated Fos expression in the infralimbic and anterior cingulate cortices, the nucleus accumbens (core and shell), bed nucleus of the stria terminalis, and ventral tegmental area, evident as a reduction relative to both PC and IC. In contrast, IC enhanced Fos expression in the dorsal caudate putamen, substantia nigra, and central amygdala, evident as an increase relative to both PC and EE. These results suggest that EE blunts neural activation throughout the mesocorticolimbic circuitry involved in cue-elicited incentive motivation for cocaine, whereas IC enhances activation primarily within the nigrostriatal dopamine pathway. These findings have important implications for understanding and treating drug-conditioned craving in humans.

Cocaine choice in humans during D-amphetamine maintenance

The results of preclinical laboratory experiments and clinical trials indicate that agonist replacements such as d-amphetamine may be a viable option for managing cocaine dependence. This study determined the effects of d-amphetamine maintenance on cocaine choice behavior in human participants. We predicted that d-amphetamine maintenance would reduce cocaine choice. Nine cocaine-dependent participants completed the study. Two d-amphetamine maintenance conditions were completed in a counterbalanced order (0 and 40 mg/d). After 3 to 5 days of placebo or d-amphetamine maintenance, the participants completed 5 experimental sessions. During these sessions, the participants first sampled the placebo (ie, 4 mg of intranasal cocaine) identified as drug A. The participants then sampled a second intranasal drug dose (4, 10, 20, or 30 mg of cocaine) identified as drug B. The participants then made 6 discrete choices between drugs A and B. Drug choices were separated by 45 minutes. The primary outcome measure was the number of cocaine choices. All doses of cocaine were chosen significantly more than placebo during both maintenance conditions (ie, placebo and d-amphetamine). Choice of the 20-mg dose of cocaine was significantly lower during d-amphetamine maintenance relative to when this cocaine dose was tested during placebo-d-amphetamine maintenance. Cocaine produced prototypical subject-rated drug effects (eg, good effects, like drug, willing to take again). These effects were not altered to a significant degree by d-amphetamine maintenance. Cocaine was well tolerated during D-amphetamine maintenance, and no unexpected or serious adverse events occurred. These results are concordant with those of previous preclinical experiments, human laboratory studies, and clinical trials that suggest that agonist replacement therapy may be a viable strategy for managing cocaine dependence.

Modeling risk factors for nicotine and other drug abuse in the preclinical laboratory

Risk factors that predict vulnerability for nicotine and other drug abuse have been identified using preclinical models, and there is close agreement with clinical and epidemiological studies. The major risk factors to be discussed are age, sex/hormonal status, impulsivity, sweet-liking, novelty reactivity, proclivity for exercise, and environmental impoverishment (vs. enrichment). This discussion will focus on factors that preclinical research has determined are strong and translatable predictors of nicotine and other drug abuse. An advantage of using preclinical models is that prospective, longitudinal studies and within-subject designs can be used to reveal risk factors that are diverse yet maintain unique characteristics. The many interrelationships among these factors lead to an additive vulnerability that increases the predictability that drug abuse will occur. A feature that these risk factors have in common is that they consistently predict vulnerability to drug abuse over critical transition phases of addiction that are difficult to examine prospectively in humans, such as acquisition, escalation, and reinstatement of drug-seeking after abstinence (relapse). The models offer valuable information that has been transferred to effective prevention and treatment strategies for smoking and other drug abuse in humans.

Cocaine effects during D-amphetamine maintenance: a human laboratory analysis of safety, tolerability and efficacy

Agonist replacement therapies are effective for managing substance abuse disorders including nicotine and opioid dependence. The results of preclinical laboratory studies and clinical trials indicate that agonist replacements like D-amphetamine may be a viable option for managing cocaine dependence. This experiment determined the physiological and behavioral effects of cocaine during D-amphetamine maintenance in seven cocaine-dependent participants. We predicted cocaine would be well tolerated during D-amphetamine maintenance. We also predicted D-amphetamine would attenuate the behavioral effects of cocaine. After 3-5 days of D-amphetamine maintenance (0, 15, and 30 mg/day), volunteers were administered ascending doses of cocaine (4, 30, 60 mg, i.n.) within a single session. Cocaine doses were separated by 90 min. Cocaine produced prototypical physiological (e.g., increased heart rate, blood pressure, and body temperature) and subject-rated (e.g., increased ratings of Good Effects) effects. During maintenance on the highest D-amphetamine dose, the heart rate increasing effects of cocaine were larger than observed during placebo maintenance. These effects were not clinically significant and no unexpected or serious adverse events were observed. D-amphetamine attenuated some of the subject-rated effects of cocaine. These results are concordant with those of previous preclinical studies, human laboratory experiments and clinical trials, further suggesting that agonist replacement therapy may be a viable strategy for managing cocaine abuse. Additional research in humans is needed to determine whether D-amphetamine attenuates the effects of cocaine under different experimental conditions (e.g., higher cocaine doses) and behavioral arrangements (e.g., drug self-administration or discrimination).

Serotonergic mechanisms in addiction-related memories

Drug-associated memories are a hallmark of addiction and a contributing factor in the continued use and relapse to drugs of abuse. Repeated association of drugs of abuse with conditioned stimuli leads to long-lasting behavioral responses that reflect reward-controlled learning and participate in the establishment of addiction. A greater understanding of the mechanisms underlying the formation and retrieval of drug-associated memories may shed light on potential therapeutic approaches to effectively intervene with drug use-associated memory. There is evidence to support the involvement of serotonin (5-HT) neurotransmission in learning and memory formation through the families of the 5-HT(1) receptor (5-HT(1)R) and 5-HT(2)R which have also been shown to play a modulatory role in the behavioral effects induced by many psychostimulants. While there is a paucity of studies examining the effects of selective 5-HT(1A)R ligands, the available dataset suggests that 5-HT(1B)R agonists may inhibit retrieval of cocaine-associated memories. The 5-HT(2A)R and 5-HT(2C)R appear to be integral in the strong conditioned associations made between cocaine and environmental cues with 5-HT(2A)R antagonists and 5-HT(2C)R agonists possessing potency in blocking retrieval of cocaine-associated memories following cocaine self-administration procedures. The complex anatomical connectivity between 5-HT neurons and other neuronal phenotypes in limbic-corticostriatal brain structures, the heterogeneity of 5-HT receptors (5-HT(X)R) and the conflicting results of behavioral experiments which employ non-specific 5-HT(X)R ligands contribute to the complexity of interpreting the involvement of 5-HT systems in addictive-related memory processes. This review briefly traces the history of 5-HT involvement in retrieval of drug-cue associations and future targets of serotonergic manipulation that may reduce the impact that drug cues have on addictive behavior and relapse.

Recent trends in adolescent substance use, primary care screening, and updates in treatment options

PURPOSE OF REVIEW

To provide a brief overview on trends in common substances of abuse in adolescents, a summary of tools to evaluate adolescent substance abuse in an outpatient setting, and an update of outpatient and inpatient treatment options.

RECENT FINDINGS

Recent national data suggest an overall slight decline in the use of tobacco, crystal methamphetamine, heroin, and club drugs. No significant change was noted in the use of alcohol, marijuana, and cocaine. Yearly screening of all adolescents for substance use is recommended. This can be accomplished in an office setting using mnemonics, structured interview techniques, and brief screens for substance abuse. If a problem is identified, various outpatient and inpatient treatments are available. Individual, family, and group therapy methods are available. Other options include acute detoxification programs, partial hospitalization, acute residential treatment, residential treatment centers and wilderness programs. Pharmacological treatments are available for nicotine, alcohol, and opioid addiction.

SUMMARY

Tobacco, alcohol, marijuana, and other drugs remain a significant problem among adolescents in the United States. Pediatricians should screen and assess all adolescents on a yearly basis. If a problem is identified, there are many options for treatment, including pharmacologic treatment as well as individual, family, or group therapy in an inpatient or outpatient setting.

Diminished nicotine withdrawal in adolescent rats: implications for vulnerability to addiction

RATIONALE

Enhanced reinforcing effects of nicotine during adolescence appear to contribute to the rapid development of dependence in this age group. However, the contribution of nicotine withdrawal to dependence in adolescents is unclear.

OBJECTIVE

We compared motivational and somatic signs of nicotine withdrawal in adolescent and adult rats.

MATERIALS AND METHODS

In experiment 1, motivational signs of nicotine withdrawal were compared using intracranial self-stimulation procedures after administration of mecamylamine (1.5 mg/kg, i.p.) in adolescent and adult rats made dependent on nicotine (9 mg/kg/day). Somatic signs of withdrawal were compared in two experiments using various doses of nicotine (adolescent doses: 0, 1.6, 3.2, 4.7 mg/kg/day; adult doses: 0, 1, 2.1, 3.2 mg/kg/day, expressed as nicotine base) to produce dependence and one dose of mecamylamine (1.5 mg/kg, i.p.) to precipitate withdrawal (experiment 2) and in a subsequent experiment, using various doses of mecamylamine (0, 0.75, 1.5, 3.0 mg/kg, i.p.) to precipitate withdrawal and a dose of nicotine (adolescent dose: 4.7 mg/kg/day; adult dose: 3.2 mg/kg/day) that produced equivalent nicotine blood levels in these age groups (experiment 3).

RESULTS

Adolescents did not display the decreases in brain reward function observed in adults experiencing withdrawal, and displayed fewer somatic signs of nicotine withdrawal relative to adults regardless of the dosing procedure used.

CONCLUSION

The negative effects of nicotine withdrawal are lower during adolescence relative to later periods of development. Both the enhanced rewarding effects and the diminished nicotine withdrawal likely contribute to the rapid development of nicotine use during adolescence.