Evaluation of subjective effects of aripiprazole and methamphetamine in methamphetamine-dependent volunteers

Pharmacological Treatments for Methamphetamine Use Disorder: Current Status and Future Targets

The illicit use of the psychostimulant methamphetamine (METH) is a major concern, with overdose deaths increasing substantially since the mid-2010s. One challenge to treating METH use disorder (MUD), as with other psychostimulant use disorders, is that there are no available pharmacotherapies that can reduce cravings and help individuals achieve abstinence. The purpose of the current review is to discuss the molecular targets that have been tested in assays measuring the physiological, the cognitive, and the reinforcing effects of METH in both animals and humans. Several drugs show promise as potential pharmacotherapies for MUD when tested in animals, but fail to produce long-term changes in METH use in dependent individuals (eg, modafinil, antipsychotic medications, baclofen). However, these drugs, plus medications like atomoxetine and varenicline, may be better served as treatments to ameliorate the psychotomimetic effects of METH or to reverse METH-induced cognitive deficits. Preclinical studies show that vesicular monoamine transporter 2 inhibitors, metabotropic glutamate receptor ligands, and trace amine-associated receptor agonists are efficacious in attenuating the reinforcing effects of METH; however, clinical studies are needed to determine if these drugs effectively treat MUD. In addition to screening these compounds in individuals with MUD, potential future directions include increased emphasis on sex differences in preclinical studies and utilization of pharmacogenetic approaches to determine if genetic variances are predictive of treatment outcomes. These future directions can help lead to better interventions for treating MUD.

Does drug use affect the efficacy of amisulpride, aripiprazole and olanzapine in patients with schizophrenia spectrum disorders? Results from a pragmatic, randomised study

OBJECTIVES

Drug use is prevalent in patients with schizophrenia spectrum disorders (SSD) but there is limited knowledge about the influence of drug use on the effectiveness of antipsychotic medication. This secondary explorative study compared the effectiveness of three antipsychotics in patients with SSD, with and without drug use.

METHODS

The BeSt InTro multi-centre, head to head, rater-blinded randomised study compared amisulpride, aripiprazole and olanzapine over a 1-year follow-up period. All patients (n = 144) were aged ≥18 years and met the ICD-10 criteria for SSD (F20-29). Clinical symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). The primary outcome was reduction of a PANSS positive subscale score.

RESULTS

At baseline, 38% of all patients reported drug use in the last 6 months before inclusion, with cannabis as the main drug (85%), followed by amphetamine-type stimulants (45%), sedatives (26%), hallucinogens (19%), cocaine (13%), opiates (4%), GHB (4%), solvents (4%), analgesics (4%) and anabolic steroids (2%). The predominant pattern was the use of several drugs. There were no significant overall differences in the PANSS positive subscale score reduction for the three studied antipsychotics among patients either with or without drug use. In the drug use group, older patients treated with amisulpride showed a greater PANSS positive subscale score reduction during the treatment period compared to younger patients.

CONCLUSION

The current study showed that drug use does not appear to affect the overall effectiveness of amisulpride, aripiprazole and olanzapine in patients with SSD. However, amisulpride may be a particularly suitable choice for older patients with drug use.

Multiple comparison of different noninvasive brain stimulation and pharmacologic interventions in patients with methamphetamine use disorders: A network meta-analysis of randomized controlled trials

AIM

In recent decades, the prevalence of amphetamine and methamphetamine use disorders has at least doubled in some regions/countries, with accompanying high risks of drug overdose-associated mortality. Noninvasive brain stimulation (NIBS) methods may be effective treatments. However, the comparative efficacy of the NIBS protocol for amphetamine/methamphetamine use disorder (AUD/MUD) remains unknown to date. The aim of this network meta-analysis (NMA) was to compare the efficacy and acceptability of various NIBS methods/protocols for AUD/MUD management.

METHODS

A frequentist model-based NMA was conducted. We included randomized controlled trials (RCTs) that investigated the efficacy of NIBS and guideline-recommended pharmacologic treatments to reduce craving severity in patients with either AUD or MUD.

RESULTS

Twenty-two RCTs including 1888 participants met the eligibility criteria. Compared with the sham/placebo group (study = 19, subjects = 891), a combination of intermittent theta burst stimulation over the left dorsolateral prefrontal cortex (DLPFC) and continuous TBS over the left ventromedial prefrontal cortex (study = 1, subjects = 19) was associated with the largest decreases in craving severity [standardized mean difference (SMD) = -1.50; 95% confidence intervals (95%CIs) = -2.70 to -0.31]. High-frequency repetitive transcranial magnetic stimulation over the left DLPFC was associated with the largest improvements in depression and quality of sleep (study = 3, subjects = 86) (SMD = -2.48; 95%CIs = -3.25 to -1.71 and SMD = -2.43; 95%CIs = -3.38 to -1.48, respectively). The drop-out rate of most investigated treatments did not significantly differ between groups.

CONCLUSION

The combined TBS protocol over the prefrontal cortex was associated with the greatest improvement in craving severity. Since few studies were available for inclusion, additional large-scale randomized controlled trials are warranted.

Biphasic reward effects are characteristic of both lorcaserin and drugs of abuse: implications for treatment of substance use disorders

Lorcaserin is a modestly selective agonist for 2C serotonin receptors (5-HT2CR). Despite early promising data, it recently failed to facilitate cocaine abstinence in patients and has been compared with dopamine antagonist medications (antipsychotics). Here, we review the effects of both classes on drug reinforcement. In addition to not being effective treatments for cocaine use disorder, both dopamine antagonists and lorcaserin can have biphasic effects on dopamine and reward behavior. Lower doses can cause enhanced drug taking with higher doses causing reductions. This biphasic pattern is shared with certain stimulants, opioids, and sedative-hypnotics, as well as compounds without abuse potential that include agonists for muscarinic and melatonin receptors. Additional factors associated with decreased drug taking include intermittent dosing for dopamine antagonists and use of progressive-ratio schedules for lorcaserin. Clinically relevant doses of lorcaserin were much lower than those that inhibited cocaine-reinforced behavior and can also augment this same behavior in different species. Diminished drug-reinforced behavior only occurred in animals after higher doses that are not suitable for use in patients. In conclusion, drugs of abuse and related compounds often act as biphasic modifiers of reward behavior, especially when evaluated over a broad range of doses. This property may reflect the underlying physiology of the reward system, allowing homeostatic influences on behavior.

Sex-dependent effects of alcohol administration on the urge to use cannabis

Alcohol and cannabis couse is highly prevalent and associated with various negative consequences. The likelihood of same day couse is high, especially among men, however, underlying mechanisms to their couse and its sex-dependent nature remain poorly understood. This study aims to elucidate the effects of controlled alcohol administration on the urge to use cannabis and considers sex-dependent effects. A community sample of non-treatment-seeking heavy drinkers (N = 37, 46% female) reporting cannabis use in the past 6 months completed an alcohol administration paradigm. Participants rated their urge to use cannabis and drink alcohol at baseline and at rising levels of breath alcohol concentration (BrAC). Mixed model analyses examined the effects of BrAC, sex, and their interaction on craving for cannabis. The relationships across urge for cannabis, urge for alcohol, and subjective responses to alcohol were also tested. There was a significant BrAC × Sex interaction on the urge to use cannabis, such that males reported increases in the urge to use cannabis at rising BrACs but females did not. Urge for alcohol significantly predicted urge for cannabis across rising levels of BrAC and this relationship was stronger in males than in females. Lastly, stimulation, but not sedation, during alcohol administration was positively associated with the urge for cannabis. Overall, these results suggest that the pharmacological effects of alcohol on the urge to use cannabis are sex-dependent and that the stimulant effects of alcohol are associated with a higher urge for cannabis. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Assessing methamphetamine-related cue reactivity in people with methamphetamine use disorder relative to controls

Methamphetamine use disorder involves methamphetamine-related cues invoking intense craving leading to relapse. Such cue reactivity is thought to arise from Pavlovian conditioning that occurs during the drug-taking experience. Cue reactivity then should be selective to methamphetamine cues (and not other cues), and not observed in people who have never experienced methamphetamine. However, these premises have never been tested and reported using objective measures such as skin conductance response (SCR). The primary aim of this study was to test these premises using a cue reactivity paradigm we developed using control cues. The secondary aim was to explore the relationship between cue reactivity, drug use characteristics, and cognition. Thirty people with a current diagnosis of methamphetamine use disorder and 30 matched controls with no history of substance use disorder were recruited. We observed higher overall subjective reactivity (F = 62.810; p < 0.001) and cue-selective physiological reactivity (F = 5.160; p = 0.026) in people with methamphetamine use disorder but not in controls. Co-morbid sedative use was associated with higher subjective craving (r = 0.521; p = 0.003). People who use methamphetamine intravenously had higher cue-selective SCR than smokers (t = 3.750; p < 0.001). Low inhibitory control measured by the Stroop task was associated with increased craving across the cue paradigm (r = -0.494; p = 0.006). Overall, these results support that cue reactivity in people with methamphetamine use disorder is due to Pavlovian conditioning. Its association with drug use and cognition highlights cue reactivity paradigm's utility in understanding methamphetamine use disorder to develop new treatments targeting cue-induced craving.

β-caryophyllene, an FDA-Approved Food Additive, Inhibits Methamphetamine-Taking and Methamphetamine-Seeking Behaviors Possibly via CB2 and Non-CB2 Receptor Mechanisms

Recent research indicates that brain cannabinoid CB2 receptors are involved in drug reward and addiction. However, it is unclear whether β-caryophyllene (BCP), a natural product with a CB2 receptor agonist profile, has therapeutic effects on methamphetamine (METH) abuse and dependence. In this study, we used animal models of self-administration, electrical brain-stimulation reward (BSR) and in vivo microdialysis to explore the effects of BCP on METH-taking and METH-seeking behavior. We found that systemic administration of BCP dose-dependently inhibited METH self-administration under both fixed-ratio and progressive-ratio reinforcement schedules in rats, indicating that BCP reduces METH reward, METH intake, and incentive motivation to seek and take METH. The attenuating effects of BCP were partially blocked by AM 630, a selective CB2 receptor antagonist. Genetic deletion of CB2 receptors in CB2-knockout (CB2-KO) mice also blocked low dose BCP-induced reduction in METH self-administration, suggesting possible involvement of a CB2 receptor mechanism. However, at high doses, BCP produced a reduction in METH self-administration in CB2-KO mice in a manner similar as in WT mice, suggesting that non-CB2 receptor mechanisms underlie high dose BCP-produced effects. In addition, BCP dose-dependently attenuated METH-enhanced electrical BSR and inhibited METH-primed and cue-induced reinstatement of drug-seeking in rats. In vivo microdialysis assays indicated that BCP alone did not produce a significant reduction in extracellular dopamine (DA) in the nucleus accumbens (NAc), while BCP pretreatment significantly reduced METH-induced increases in extracellular NAc DA in a dose-dependent manner, suggesting a DA-dependent mechanism involved in BCP action. Together, the present findings suggest that BCP might be a promising therapeutic candidate for the treatment of METH use disorder.

Evidence for the Confluence of Cigarette Smoking, Other Substance Use, and Psychosocial and Mental Health in a Sample of Urban Sexual Minority Young Adults: The P18 Cohort Study

BACKGROUND

Sexual minority men (SMM) and transgender women (TW) are more likely to smoke cigarettes than heterosexual and cisgender peers, which may exacerbate existing disparities in mental and psychosocial health and substance use.

PURPOSE

As few existing studies have examined the confluence of these factors, we sought to examine tobacco use in a diverse sample of SMM and TW and describe its relationship with other substance use and health.

METHODS

Data were drawn from a study of syndemic conditions among SMM and TW, which included measures assessing tobacco use, substance use, and mental, psychosocial, and general health.

RESULTS

A majority of the racially/ethnically and socioeconomically diverse sample (n = 665) reported ever smoking a cigarette, and more than half of them were current smokers. Current smoking was associated with more frequent recent substance use and poorer mental, psychosocial, and general health. In multivariable analyses, current smoking was predicted by more frequent substance use and more severe anxiety, when adjusting for demographic, substance use, and health factors.

CONCLUSIONS

A syndemic approach to health conditions such as substance use, mental health, and psychosocial burden dictates a framework of interrelation and mutual exacerbation. In doing so, we found that current cigarette use was associated with more frequent alcohol and marijuana use and more severe anxiety, suggesting a confluence of cigarette smoking, other substance use, and mental health burden. We recommend a holistic approach to treating tobacco use in sexual and gender minority populations that addresses both substance use and the myriad psychosocial burdens that sexual and gender minority communities experience.

A Scoping Review on Cue Reactivity in Methamphetamine Use Disorder

The experience of craving via exposure to drug-related cues often leads to relapse in drug users. This study consolidated existing empirical evidences of cue reactivity to methamphetamine to provide an overview of current literature and to inform the directions for future research. The best practice methodological framework for conducting scoping review by Arkey and O'Malley was adopted. Studies that have used a cue paradigm or reported on cue reactivity in persons with a history of methamphetamine use were included. Databases such as Medline, EMBASE, PsycINFO and CINAHL were searched using key terms, in addition to citation check and hand search. The search resulted in a total of 32 original research articles published between 2006 to 2020. Three main themes with regard to cue reactivity were identified and synthesized: (1) effects of cue exposure, (2) individual factors associated with cue reactivity, and (3) strategies that modulate craving or reactivity to cues. Exposure to methamphetamine-associated cues elicits significant craving and other autonomic reactivity. Evidence suggests that drug cue reactivity is strongly associated with indices of drug use and other individual-specific factors. Future studies should focus on high quality studies to support evidence-based interventions for reducing cue reactivity and to examine cue reactivity as an outcome measure.

Executive function moderates naltrexone effects on methamphetamine-induced craving and subjective responses

Background: Emerging evidence suggests that opioid receptor antagonists, such as naltrexone, are effective pharmacotherapies for alcohol, opioid, and possibly stimulant use disorders. It is posited that naltrexone exerts its effects, in part, by increasing functional connectivity between neural reward circuitry and frontal systems implicated in executive function. Yet no studies had examined whether executive function moderates these effects. Objectives: This study examined whether a composite measure of executive function (EF) moderates the effect of naltrexone on craving for methamphetamine and subjective responses following infusion of the drug. Methods: Individuals with methamphetamine use disorder (N = 30; 27% female) completed baseline neurocognitive assessments of premorbid and executive function, and an executive function factor was computed. Participants then underwent a randomized, double-blind, cross-over study of titration with naltrexone and placebo. Participants then received a 30-mg intravenous methamphetamine infusion and completed subjective response questionnaires at 8 times in the 120 minutes post-infusion. Results: Multilevel mixed models indicated a significant EF × medication interaction, reflecting greater effects of naltrexone to decrease "desire to access the drug", "want more of the drug", "crave the drug", "feel drug effects" and "feel high" in participants with low EF compared to those with high EF (Bs = .36-1.29, SEs = .14-.17, ps<0.01). These effects remained significant after controlling for premorbid cognitive functioning, baseline responses to methamphetamine, severity of methamphetamine use, and methamphetamine-related functional problems. Conclusion: Naltrexone may be especially effective in methamphetamine-dependent individuals with low EF. Neuropsychological assessments may also provide predictive clinical utility not captured by traditional measures of substance use severity.

Drug-Induced Craving for Methamphetamine Is Associated With Neural Methamphetamine Cue Reactivity

OBJECTIVE

Drug craving serves as the major motivator to propagate drug use and is thought to elicit relapse in abstinent individuals. Although craving for methamphetamine has been investigated using both laboratory and neuroimaging methodologies, the relationship between drug-induced craving and neural responses to methamphetamine cues has yet to be explored. Therefore, the present study investigated whether methamphetamine-induced craving responses in the laboratory were associated with neural response to methamphetamine cues.

METHOD

Non-treatment-seeking individuals with methamphetamine use disorder (n = 15) completed two sessions, one in the laboratory where they underwent a methamphetamine infusion, and one in the magnetic resonance imaging scanner where they viewed methamphetamine cues. Participants reported their craving for methamphetamine over the course of the laboratory session. Analyses examined the association between peak ratings of methamphetamine-induced craving and neural activation to methamphetamine cues.

RESULTS

In individuals with a methamphetamine use disorder, methamphetamine-induced craving was positively associated with neural methamphetamine cue reactivity in the precuneus, putamen, and ventromedial prefrontal cortex (Z > 2.3, p < .05).

CONCLUSIONS

There is a shared neurobiology underlying cue- and drug-induced craving in individuals with methamphetamine use disorder. Treatments that disrupt this circuitry may decrease craving and help prevent relapse.

Drug-Induced Craving for Methamphetamine Is Associated With Neural Methamphetamine Cue Reactivity

OBJECTIVE

Drug craving serves as the major motivator to propagate drug use and is thought to elicit relapse in abstinent individuals. Although craving for methamphetamine has been investigated using both laboratory and neuroimaging methodologies, the relationship between drug-induced craving and neural responses to methamphetamine cues has yet to be explored. Therefore, the present study investigated whether methamphetamine-induced craving responses in the laboratory were associated with neural response to methamphetamine cues.

METHOD

Non-treatment-seeking individuals with methamphetamine use disorder (n = 15) completed two sessions, one in the laboratory where they underwent a methamphetamine infusion, and one in the magnetic resonance imaging scanner where they viewed methamphetamine cues. Participants reported their craving for methamphetamine over the course of the laboratory session. Analyses examined the association between peak ratings of methamphetamine-induced craving and neural activation to methamphetamine cues.

RESULTS

In individuals with a methamphetamine use disorder, methamphetamine-induced craving was positively associated with neural methamphetamine cue reactivity in the precuneus, putamen, and ventromedial prefrontal cortex (Z > 2.3, p < .05).

CONCLUSIONS

There is a shared neurobiology underlying cue- and drug-induced craving in individuals with methamphetamine use disorder. Treatments that disrupt this circuitry may decrease craving and help prevent relapse.

Naltrexone moderates the relationship between cue-induced craving and subjective response to methamphetamine in individuals with methamphetamine use disorder

RATIONALE

Reductions in cue-induced craving and subjective response to drugs of abuse are commonly used as initial outcome measures when testing novel medications for the treatment of addiction. Yet neither the relationship between these two measures at the individual level nor the moderating effects of pharmacotherapies on this relationship has been examined.

OBJECTIVE

This secondary data analysis sought to examine (1) the predictive relationship between cue-induced craving and subsequent acute subjective response to methamphetamine (MA) and (2) whether the opioid-receptor antagonist naltrexone moderated this association in a sample of non-treatment-seeking individuals who met DSM-IV criteria for MA use disorder (abuse or dependence).

METHODS

Participants (n = 30) completed two 4-day medication regimens (oral naltrexone 50 mg or placebo, in a randomized, counterbalanced, and double-blind fashion). On day 4 of each medication regimen, participants completed a cue-reactivity paradigm followed by intravenous MA administration. Methamphetamine craving was assessed after the cue-reactivity paradigm, and subjective response to MA was assessed during MA infusion.

RESULTS

Cue-induced craving for MA was positively associated with post-infusion subjective MA effects, including positive (i.e., stimulation, good effects, feel drug, high), negative (i.e., anxious and depressed), and craving-related (i.e., want more, would like access to drug, crave) responses. Naltrexone, vs. placebo, significantly reduced the association between cue-induced craving and positive subjective response to MA.

CONCLUSIONS

The findings indicate that naltrexone moderates the predictive relationship between cue-induced craving and positive subjective effects of MA, thereby suggesting a behavioral mechanism by which naltrexone may be efficacious in treating MA use disorder.

Pharmacotherapeutic agents in the treatment of methamphetamine dependence

INTRODUCTION

Methamphetamine use is a serious public health concern in many countries and is second to cannabis as the most widely abused illicit drug in the world. Effective management for methamphetamine dependence remains elusive and the large majority of methamphetamine users relapse following treatment. Areas covered: Progression in the understanding of the pharmacological basis of methamphetamine use has provided us with innovative opportunities to develop agents to treat dependence. The current review summarizes relevant literature on the neurobiological and clinical correlates associated with methamphetamine use. We then outline agents that have been explored for potential treatments in preclinical studies, human laboratory phase I and phase II trials over the last ten years. Expert opinion: No agent has demonstrated a broad and strong effect in achieving MA abstinence in Phase II trials. Agents with novel therapeutic targets appear promising. Advancement in MA treatment, including translation into practice, faces several clinical challenges.

The cross-talk of HIV-1 Tat and methamphetamine in HIV-associated neurocognitive disorders

Antiretroviral therapy has dramatically improved the lives of human immunodeficiency virus 1 (HIV-1) infected individuals. Nonetheless, HIV-associated neurocognitive disorders (HAND), which range from undetectable neurocognitive impairments to severe dementia, still affect approximately 50% of the infected population, hampering their quality of life. The persistence of HAND is promoted by several factors, including longer life expectancies, the residual levels of virus in the central nervous system (CNS) and the continued presence of HIV-1 regulatory proteins such as the transactivator of transcription (Tat) in the brain. Tat is a secreted viral protein that crosses the blood–brain barrier into the CNS, where it has the ability to directly act on neurons and non-neuronal cells alike. These actions result in the release of soluble factors involved in inflammation, oxidative stress and excitotoxicity, ultimately resulting in neuronal damage. The percentage of methamphetamine (MA) abusers is high among the HIV-1-positive population compared to the general population. On the other hand, MA abuse is correlated with increased viral replication, enhanced Tat-mediated neurotoxicity and neurocognitive impairments. Although several strategies have been investigated to reduce HAND and MA use, no clinically approved treatment is currently available. Here, we review the latest findings of the effects of Tat and MA in HAND and discuss a few promising potential therapeutic developments.

The Effects of Naltrexone on Subjective Response to Methamphetamine in a Clinical Sample: a Double-Blind, Placebo-Controlled Laboratory Study

Methamphetamine (MA) use disorder is a serious psychiatric condition for which there are no FDA-approved medications. Naltrexone (NTX) is an opioid receptor antagonist with demonstrated efficacy, albeit moderate, for the treatment of alcoholism and opioid dependence. Preclinical and clinical studies suggest that NTX may be useful for the treatment of MA use disorder. To inform treatment development, we conducted a double-blind, randomized, crossover, placebo-controlled human laboratory study of NTX. Non-treatment-seeking individuals meeting DSM-IV criteria for MA abuse or dependence (n=30) completed two separate 5-day inpatient stays. During each admission, participants completed testing sessions comprised of MA cue-reactivity and intravenous MA administration (30 mg) after receiving oral NTX (50 mg) or placebo for 4 days. This study tested the hypotheses that NTX would (a) attenuate cue-induced MA craving, and (b) reduce subjective responses to MA administration. Results largely supported the study hypotheses such that (a) NTX significantly blunted cue-induced craving for MA and (b) attenuated several of the hedonic subjective effects of MA, including craving, during controlled MA administration and as compared with placebo. NTX decreased overall subjective ratings of 'crave drug,' 'stimulated,' and 'would like drug access,' decreased the the post-MA administration timecourse of 'anxious' and increased ratings of 'bad drug effects,' as compared with placebo. These findings support a potential mechanism of action by showing that NTX reduced cue-induced craving and subjective responses to MA. This is consistent with positive treatment studies of NTX for amphetamine dependence, as well as ongoing clinical trials for MA.

Dopamine D3 receptors as a therapeutic target for methamphetamine dependence

BACKGROUND

Methamphetamine (MA) use disorders are major public health problems nationally and worldwide and treatment remains an unmet need.

OBJECTIVES

(1) To review preclinical and clinical studies identifying the dopamine D3 receptor as a therapeutic target for substance use disorders (SUDs), including MA dependence, (2) to consider buspirone (Buspar®) as a potential medication based on its dopamine D3 receptor antagonist properties, and (3) to evaluate the safety and initial efficacy of buspirone in a pilot study of MA-dependent individuals.

METHODS

Literature on the dopamine D3 receptor as a therapeutic target and on the potential of buspirone as a novel therapy for MA dependence was reviewed. The cardiovascular and subjective effects of intravenous MA challenge were assessed in five non-treatment seeking individuals. Participants met DSM-IV criteria for MA dependence and were treated subacutely (9 days) with buspirone (60 mg daily).

RESULTS

The literature identified the dopamine D3 receptor as a therapeutic target for MA dependence, a safe and approved medication, and a valuable opportunity to re-purpose buspirone for treating MA dependence and perhaps other SUDs. Pilot data (n = 5) indicated that buspirone is safe in MA-using individuals and comparison against historical placebo data from this laboratory suggested that at least some aspects of the subjective properties of MA may be diminished during buspirone treatment.

CONCLUSION

Future studies should include a small-scale, placebo-controlled Phase IIa trial of buspirone in MA dependence.

Methamphetamine: an update on epidemiology, pharmacology, clinical phenomenology, and treatment literature

BACKGROUND

Despite initial reports of a decline in use in the early 2000s, methamphetamine remains a significant public health concern with known neurotoxic and neurocognitive effects to the user. The goal of this review is to update the literature on methamphetamine use and addiction since its assent to peak popularity in 1990s.

METHODS

We first review recent epidemiological reports with a focus on methamphetamine accessibility, changes in use and disorder prevalence rates over time, and accurate estimates of the associated burden of care to the individual and society. Second, we review methamphetamine pharmacology literature with emphasis on the structural and functional neurotoxic effects associated with repeated use of the drug. Third, we briefly outline the findings on methamphetamine-related neurocognitive deficits as assessed via behavioral and neuroimaging paradigms. Lastly, we review the clinical presentation of methamphetamine addiction and the evidence supporting the available psychosocial and pharmacological treatments within the context of an addiction biology framework.

CONCLUSION

Taken together, this review provides a broad-based update of the available literature covering methamphetamine research over the past two decades and concludes with recommendations for future research.

Short-term, low-dose varenicline administration enhances information processing speed in methamphetamine-dependent users

Long-term, high-dose methamphetamine (METH) use is associated with decrements in neurocognition and, given the association between impaired neurocognition and poorer treatment outcomes in individuals dependent on alcohol and drugs, it is considered to be a neglected area of critical concern. The objective of this study was to determine whether varenicline, a partial agonist at α4β2- and a full agonist at α7-nicotinic acetylcholine receptors, enhances attention/information processing speed, episodic memory, and working memory in non-treatment seeking METH-dependent participants. Twenty-six participants were randomly assigned to receive oral placebo or oral varenicline (titrated up to 1 mg) over 5 days during three separate inpatient phases, and 17 completed each inpatient phase. Participants were predominately male (71%) and Caucasian (71%). Varenicline significantly improved reaction time on the n-back for visual stimuli (F(1,47)=5.369, p=0.025, η2=0.103), and a trend was observed for improvement in reaction time for auditory stimuli (F(1,47)=3.141, p=0.083, η2=0.063). For those study participants whose reaction time was in the lower half of the distribution at baseline, the effect was even more pronounced for auditory (F(1,22)=5.287, p=0.031, η2=0.194) and visual (F(1,22)=11.981, p=0.002, η2=0.353) stimuli relative to placebo. In contrast, varenicline did not modulate mean or maximum span of working memory or performance on tests of episodic memory or attention (p's>0.05). Given the potential importance of this finding, it should be replicated in a larger sample over a longer treatment period with a higher dose of varenicline (2 mg).

TRIAL REGISTRATION

clinicalTrials.gov Identifier NCT01571167.

Influence of aripiprazole pretreatment on the reinforcing effects of methamphetamine in humans

Methamphetamine use disorders remain a significant public health concern. Methamphetamine produces its behavioral effects by facilitating release of monoamines like dopamine (DA) and serotonin (5-HT). Results from animal studies show that acute pretreatment with DA and 5-HT antagonists attenuates the effects of methamphetamine, but this area remains largely unexplored in humans. This study sought to assess whether aripiprazole, a partial agonist at D2/5-HT1A receptors and an antagonist at 5-HT2A receptors, would attenuate the reinforcing and subject-rated effects of oral methamphetamine. Seven subjects with histories of recreational stimulant use completed a placebo-controlled, crossover, double-blind protocol in which they first sampled doses of oral methamphetamine (0, 4, 8 or 16 mg) following acute pretreatment with aripiprazole (0 and 15 mg). During each Sampling Session, subjects also completed a battery of subject-rated, cardiovascular, and other performance measures. In subsequent Self-Administration Sessions, subjects were provided the opportunity to earn the previously sampled methamphetamine dose on a progressive-ratio procedure. Methamphetamine functioned as a reinforcer, and produced prototypical stimulant-like subject-rated and cardiovascular effects (e.g., increased ratings of Stimulated; elevated blood pressure). Aripiprazole reduced methamphetamine self-administration and attenuated some of the positive subject-rated effects of methamphetamine (e.g., ratings of Like Drug). These results indicate that acute aripiprazole pretreatment attenuates the abuse-related effects of methamphetamine.

96-hour methamphetamine self-administration in male and female rats: a novel model of human methamphetamine addiction

Methamphetamine (MA) is a highly addictive psychostimulant drug of abuse for which no FDA-approved treatment exists. While high on MA, both male and female MA users report engaging in risky behaviors and are more likely to be involved in violent criminal activities and to engage in domestic and sexual violence. A unique aspect of MA is that it is typically used in binges. However, there is no animal model of MA self-administration that appears to represent a human MA self-administration binge. We recently developed a 96-hour MA self-administration paradigm in rats that more closely resembles how human MA users take the drug. Male and female rats were trained to self-administer MA for 96 consecutive hours for 5 weeks. Responding by female and male rats tended to escalate to binge-like behavior, as the animals responded continuously during their normal periods of activity as well as during their inactive periods for up to 72 h, followed by a crash of 6 or more hours. Thus, this 96-hour model of MA self-administration is a novel way to study MA addition in rats that may contribute to the development of improved treatments for recovering human MA users.

A randomized, placebo-controlled trial of aripiprazole for the treatment of methamphetamine dependence and associated psychosis

OBJECTIVES

The objectives of this study were to determine the efficacy and safety of aripiprazole for treatment of psychosis, retention and abstinence in patients with methamphetamine dependence.

METHODS

This was a double-blind study where 37 methamphetamine dependent patients with history of psychosis were randomly assigned to receive aripiprazole (5-10 mg daily, N = 19) or placebo (N = 18) for 8 weeks. Follow-up evaluation was scheduled on day 7, 14, 28, 42 day 56 after enrolment.

RESULTS

Participants on aripiprazole were retained significantly longer in treatment (48.7 days, SD =4.0) compared to placebo (37.1 days, SD =5.0). The Kaplan-Meier survival analysis showed that participants on aripiprazole were less likely to drop out of the study than the placebo group (P =0.02, χ(2) =5.3). Psychotic symptoms significantly decreased among those on aripiprazole as compared to placebo (P < 0.05). However, no statistically significance was found between the two groups in maintaining abstinence (generalised estimation equation (GEE) analysis, P = 0.41). No serious adverse events were reported in either group.

CONCLUSION

Aripiprazole was no more effective than placebo in maintaining abstinence from methamphetamine use. However, it facilitated treatment retention and reduced the severity of psychotic symptoms. Aripiprazole was found to be generally safe and well tolerated.

Methamphetamine use: a comprehensive review of molecular, preclinical and clinical findings

Methamphetamine (MA) is a highly addictive psychostimulant drug that principally affects the monoamine neurotransmitter systems of the brain and results in feelings of alertness, increased energy and euphoria. The drug is particularly popular with young adults, due to its wide availability, relatively low cost, and long duration of psychoactive effects. Extended use of MA is associated with many health problems that are not limited to the central nervous system, and contribute to increased morbidity and mortality in drug users. Numerous studies, using complementary techniques, have provided evidence that chronic MA use is associated with substantial neurotoxicity and cognitive impairment. These pathological effects of the drug, combined with the addictive properties of MA, contribute to a spectrum of psychosocial issues that include medical and legal problems, at-risk behaviors and high societal costs, such as public health consequences, loss of family support and housing instability. Treatment options include pharmacological, psychological or combination therapies. The present review summarizes the key findings in the literature spanning from molecular through to clinical effects.

Aripiprazole for the treatment of methamphetamine dependence: a randomized, double-blind, placebo-controlled trial

AIMS

To test aripiprazole for efficacy in decreasing use in methamphetamine-dependent adults, compared to placebo.

DESIGN

Participants were randomized to receive 12 weeks of aripiprazole or placebo, with a 3-month follow-up and a platform of weekly 30-minute substance abuse counseling.

SETTING

The trial was conducted from January 2009 to March 2012 at the San Francisco Department of Public Health.

PARTICIPANTS

Ninety actively using, methamphetamine-dependent, sexually active adults were recruited from community venues.

MEASUREMENTS

The primary outcome was regression estimated reductions in weekly methamphetamine-positive urines. Secondary outcomes were study medication adherence [by self-report and medication event monitoring systems (MEMS)], sexual risk behavior and abstinence from methamphetamine.

FINDINGS

Participant mean age was 38.7 years, 87.8% were male, 50.0% white, 18.9% African American, and 16.7% Latino. Eighty-three per cent of follow-up visits and final visits were completed. By intent-to-treat, participants assigned to aripiprazole had similar reductions in methamphetamine-positive urines as participants assigned to placebo [risk ratio (RR) 0.88, 95% confidence interval (CI): 0.66-1.19, P = 0.41]. Urine positivity declined from 73% (33 of 45 participants) to 45% (18 of 40) in the placebo arm and from 77% (34 of 44) to 44% (20 of 35) in the aripiprazole arm. Adherence by MEMS and self-report was 42 and 74%, respectively, with no significant difference between arms (MEMS P = 0.31; self-report P = 0.17). Most sexual risk behaviors declined similarly among participants in both arms (all P > 0.05). There were no serious adverse events related to study drug, although participants randomized to aripiprazole reported more akathisia, fatigue and drowsiness (P < 0.05).

CONCLUSION

Compared with placebo, aripiprazole did not reduce methamphetamine use significantly among actively using, dependent adults.

Pharmacotherapeutics directed at deficiencies associated with cocaine dependence: focus on dopamine, norepinephrine and glutamate

Much effort has been devoted to research focused on pharmacotherapies for cocaine dependence yet there are no FDA-approved medications for this brain disease. Preclinical models have been essential to defining the central and peripheral effects produced by cocaine. Recent evidence suggests that cocaine exerts its reinforcing effects by acting on multiple neurotransmitter systems within mesocorticolimibic circuitry. Imaging studies in cocaine-dependent individuals have identified deficiencies in dopaminergic signaling primarily localized to corticolimbic areas. In addition to dysregulated striatal dopamine, norepinephrine and glutamate are also altered in cocaine dependence. In this review, we present these brain abnormalities as therapeutic targets for the treatment of cocaine dependence. We then survey promising medications that exert their therapeutic effects by presumably ameliorating these brain deficiencies. Correcting neurochemical deficits in cocaine-dependent individuals improves memory and impulse control, and reduces drug craving that may decrease cocaine use. We hypothesize that using medications aimed at reversing known neurochemical imbalances is likely to be more productive than current approaches. This view is also consistent with treatment paradigms used in neuropsychiatry and general medicine.

Treatments for methamphetamine abuse: a literature review for the clinician

Methamphetamine (METH) use and dependence is a serious public health concern with implications across multiple areas from societal impact to burden on psychiatric and medical resources. An estimated 8% of admissions to substance abuse treatment programs are related to stimulants with METH/amphetamine abuse. To date, effective pharmacotherapy options to enhance abstinence have not been identified. The objective of this article is to critically review the literature of METH treatment options. Preclinical research and human research with compounds not yet available commercially in the United States will not be included. A literature review was conducted for research on pharmacological treatments for METH use and addiction. Trial information on the use of sertraline, bupropion, mirtazapine, modafinil, dextroamphetamine, ondansetron, risperidone, aripiprazole, baclofen, and gabapentin was reviewed. Aripiprazole trials appeared in the reviewed literature more frequently than the other medications. Based on the findings of this review, no single medication demonstrated consistent efficacy and each trial contained a variety of methodological limitations.

Discriminative stimulus, subject-rated and cardiovascular effects of cocaine alone and in combination with aripiprazole in humans

Aripiprazole is a dopamine D(2) receptor partial agonist undergoing evaluation as a pharmacotherapy for stimulant-use disorders. Acutely administered aripiprazole attenuates the discriminative stimulus and other behavioral effects of d-amphetamine in humans; however, whether aripiprazole attenuates the effects of more commonly abused stimulants is unknown. The aim of this experiment was to assess the discriminative stimulus, subject-rated and cardiovascular effects of oral cocaine alone and following acute administration of aripiprazole in humans. Eight cocaine-dependent subjects learned to discriminate 150 mg cocaine from placebo. After acquiring the discrimination, the effects of cocaine (0, 25, 50, 100 and 200 mg) administered alone and in combination with aripiprazole (15 mg) were determined. Significant effects of cocaine were observed for the drug discrimination task, stimulant-like subject-rated effects and heart rate. Limited effects of aripiprazole were revealed. However, for most measures, fewer doses of cocaine were significantly greater than placebo when combined with aripiprazole, suggesting a reduction in the discriminative stimulus, self-reported and cardiovascular effects of cocaine. These data are consistent with previous studies that have tested acutely administered aripiprazole in combination with d-amphetamine and suggest that the ability of aripiprazole to modify stimulant effects is a function of the duration of treatment (acute vs. chronic).

Aripiprazole maintenance increases smoked cocaine self-administration in humans

RATIONALE

Partial dopamine receptor agonists have been proposed as candidate pharmacotherapies for cocaine dependence.

OBJECTIVE

This 42-day, within-subject, human laboratory study assessed how maintenance on aripiprazole, a partial D(2) receptor agonist, influenced smoked cocaine self-administration, cardiovascular measures, subjective effects, and cocaine craving in nontreatment-seeking, cocaine-dependent volunteers.

METHODS

In order to achieve steady-state concentrations, participants (n = 8 men) were administered placebo and aripiprazole (15 mg/day) capsules in counter-balanced order for 21 days. A smoked cocaine dose-response curve (0, 12, 25, 50 mg) was determined twice under placebo and aripiprazole maintenance. Sessions comprised a "sample" trial, when participants smoked the cocaine dose available that session, and five choice trials, when they responded on a progressive-ratio schedule of reinforcement to receive the cocaine dose or receive $5.00.

RESULTS

Cocaine's reinforcing, subjective, and cardiovascular effects were dose-dependent. Aripiprazole significantly increased cocaine (12, 25 mg) self-administration. Following a single administration of cocaine (25 mg), aripiprazole decreased ratings of how much participants would pay for that dose. Following repeated cocaine (50 mg) self-administration, aripiprazole decreased ratings of cocaine quality, craving, and good drug effect as compared to placebo.

CONCLUSIONS

These data suggest that aripiprazole may have increased self-administration to compensate for a blunted subjective cocaine effect. Overall, the findings do not suggest aripiprazole would be useful for treating cocaine dependence.

Absence of psychostimulant effects of a supratherapeutic dose of tianeptine: a placebo-controlled study versus methylphenidate in young healthy volunteers

OBJECTIVE

The primary objective of the present study was to assess the potential psychostimulant effect of a single oral supratherapeutic dose of tianeptine (75 mg in 1 shot) in young healthy volunteers compared with methylphenidate (40 mg) and placebo.

METHOD

Eighteen healthy young male and female volunteers with no history of psychostimulant abuse completed this balanced, crossover, placebo-controlled study. Subjective and behavioral effects were assessed before treatment and 1, 2, 3, 4, and 8 hours after drug intake. Subjective effects of the drugs were recorded using self-questionnaire Addiction Research Center Inventory (ARCI 49). In addition, the Profile of Mood Scale, Visual Analog Scale, and attention/vigilance tests (choice reaction time and critical flicker fusion test) were used to evaluate mood state, subjective feeling, and sustained attention, respectively.

RESULTS

Analysis on changes from baseline, from 1 to 8 hours, showed statistically significant differences between treatment groups for 2 of the 5 ARCI subscales: amphetamine and morphine benzedrine scales. A trend to significance was observed for Lysergic Acid Diethylamide scale. Indeed, although tianeptine did not significantly change any ARCI scores, methylphenidate significantly increased amphetamine and morphine benzedrine scores of the ARCI compared with placebo. No significant treatment effect was observed on the Profile of Mood Scale and the visual analog scale. Analyses of attention and vigilance tests showed a psychostimulant effect for methylphenidate on choice reaction time (decrease of recognition time) and critical flicker fusion test (higher frequency).

CONCLUSIONS

A single administration of a supratherapeutic dose of tianeptine does not induce psychostimulant effect in young healthy volunteers in contrast to methylphenidate at a therapeutic dose. These findings suggest an absence of psychostimulant liability of tianeptine in a therapeutic situation.

Discriminative-stimulus, subject-rated, and physiological effects of methamphetamine in humans pretreated with aripiprazole

Methamphetamine is thought to produce its behavioral effects by facilitating release of dopamine, serotonin (5-HT) and norepinephrine. Results from animal studies support this notion, whereas results from human laboratory studies have not consistently demonstrated the importance of monoamine systems in the behavioral effects of methamphetamine. Human drug-discrimination procedures are well suited to assess neuropharmacological mechanisms of the training drug by studying pharmacological manipulation. In this human laboratory study, 6 participants with a history of recreational stimulant use learned to discriminate 10 mg oral methamphetamine. After acquiring the discrimination (ie, ≥ 80% correct responding on 4 consecutive sessions), the effects of a range of doses of methamphetamine (0, 2.5, 5, 10, and 15 mg), alone and in combination with 0 and 20 mg aripiprazole (a partial agonist at D2 and 5-HT1A receptors), were assessed. Methamphetamine alone functioned as a discriminative stimulus, produced prototypical stimulant-like subject-rated drug effects (eg, increased ratings of Good Effects, Talkative-Friendly, and Willing to Pay For) and elevated cardiovascular indices. These effects were generally a function of dose. Aripiprazole alone did not occasion methamphetamine-appropriate responding or produce subject-rated effects but modestly impaired performance. Administration of aripiprazole significantly attenuated the discriminative-stimulus and cardiovascular effects of methamphetamine, as well as some of the subject-rated drug effects. These results indicate that monoamine systems likely play a role in the behavioral effects of methamphetamine in humans. Moreover, given the concordance between past results with d-amphetamine and the present findings, d-amphetamine can likely serve as a model for the pharmacological effects of methamphetamine.

Preclinical evidence of new opioid modulators for the treatment of addiction

IMPORTANCE OF THE FIELD

Addiction to opiates is one of the most severe forms of substance dependence, and despite a variety of pharmacological approaches to treat it, relapse is observed in a high percentage of subjects. New pharmacological compounds are necessary to improve the outcome of treatments and reduce adverse side effects. Moreover, drugs that act on the opioid system can also be of benefit in the treatment of alcohol or cocaine addiction. AREA COVERED BY THIS REVIEW: Recent preclinical studies of pharmacological agents for the treatment of opiate addiction (2008 to the present date).

WHAT THE READER WILL GAIN

The reader will be informed of the latest drugs shown in animal models to modify dependence on opiates and the reinforcing effects of these drugs. In addition, reports of the latest studies to test these compounds in models of other drug addictions are reviewed.

TAKE HOME MESSAGE

The classic clinical pharmacotherapy for opiate dependence, involving mu-opioid receptor agonists or antagonists, has not yielded a high success rate in humans. In pharmacotherapy for opioid dependence, new options are emerging and different pharmacological strategies are now being tested.

The clinical toxicology of metamfetamine

INTRODUCTION

Metamfetamine is a highly addictive amfetamine analog that acts primarily as a central nervous system (CNS) stimulant. The escalating abuse of this drug in recent years has lead to an increasing burden upon health care providers. An understanding of the drug's toxic effects and their medical treatment is therefore essential for the successful management of patients suffering this form of intoxication.

AIM

The aim of this review is to summarize all main aspects of metamfetamine poisoning including epidemiology, mechanisms of toxicity, toxicokinetics, clinical features, diagnosis, and management.

METHODS

A summary of the literature on metamfetamine was compiled by systematically searching OVID MEDLINE and ISI Web of Science. Further information was obtained from book chapters, relevant news reports, and web material. Epidemiology. Following its use in the Second World War, metamfetamine gained popularity as an illicit drug in Japan and later the United States. Its manufacture and use has now spread to include East and South-East Asia, North America, Mexico, and Australasia, and its world-wide usage, when combined with amfetamine, exceeds that of all other drugs of abuse except cannabis. Mechanisms of toxicity. Metamfetamine acts principally by stimulating the enhanced release of catecholamines from sympathetic nerve terminals, particularly of dopamine in the mesolimbic, mesocortical, and nigrostriatal pathways. The consequent elevation of intra-synaptic monoamines results in an increased activation of central and peripheral α±- and β-adrenergic postsynaptic receptors. This can cause detrimental neuropsychological, cardiovascular, and other systemic effects, and, following long-term abuse, neuronal apoptosis and nerve terminal degeneration. Toxicokinetics. Metamfetamine is rapidly absorbed and well distributed throughout the body, with extensive distribution across high lipid content tissues such as the blood-brain barrier. In humans the major metabolic pathways are aromatic hydroxylation producing 4-hydroxymetamfetamine and N-demethylation to form amfetamine. Metamfetamine is excreted predominantly in the urine and to a lesser extent by sweating and fecal excretion, with reported terminal half-lives ranging from ∼5 to 30 h. Clinical features. The clinical effects of metamfetamine poisoning can vary widely, depending on dose, route, duration, and frequency of use. They are predominantly characteristic of an acute sympathomimetic toxidrome. Common features reported include tachycardia, hypertension, chest pain, various cardiac dysrhythmias, vasculitis, headache, cerebral hemorrhage, hyperthermia, tachypnea, and violent and aggressive behaviour. Management. Emergency stabilization of vital functions and supportive care is essential. Benzodiazepines alone may adequately relieve agitation, hypertension, tachycardia, psychosis, and seizure, though other specific therapies can also be required for sympathomimetic effects and their associated complications.

CONCLUSION

Metamfetamine may cause severe sympathomimetic effects in the intoxicated patient. However, with appropriate, symptom-directed supportive care, patients can be expected to make a full recovery.

Long-term treatment with aripiprazole on the waking and postprandial urges to smoke in Chinese heavy smokers

The central dopaminergic system plays a critical role in the reinforcing effects of nicotine, which are key determinants in the urge to smoke. Previous study has demonstrated that immediate administration of 10-mg aripiprazole significantly decreased various subjective responses to smoking. The present study investigated whether 2-week treatment with 10-mg aripiprazole could attenuate waking and postprandial urges to smoke in Chinese male and female heavy smokers. A randomized and placebo-controlled pilot clinical study was conducted to assess the effect of aripiprazole on various responses to smoking. The primary outcomes were subject's ratings on questionnaires of smoking urge, withdrawal syndromes, and cigarette evaluation. All participants were administered either placebo or 10-mg aripiprazole for 2 weeks. Throughout the experiment, participants were required to self-report (1) smoking urge and nicotine withdrawal symptoms before their first cigarette after awakening and after lunch and (2) subjective responses to the first cigarette smoked of the day and after lunch. Aripiprazole was associated with significantly decreased waking and postprandial urges to smoke. Aripiprazole failed to produce a significant effect on overall nicotine withdrawal symptoms after awakening and after lunch. However, waking, but not postprandial, withdrawal craving and syndromes were significantly reduced by aripiprazole. Aripiprazole had no effect on the overall subjective responses to the first cigarette of the day and after lunch. The attenuating effects of aripiprazole on waking and postprandial urges to smoke demonstrate the promising effect of aripiprazole in the treatment of nicotine dependence.

Pharmacological approaches to methamphetamine dependence: a focused review

Methamphetamine dependence is a serious worldwide public health problem with major medical, psychiatric, socioeconomic and legal consequences. Various neuronal mechanisms implicated in methamphetamine dependence have suggested several pharmacological approaches. A literature search from a range of electronic databases (PubMed, EMBASE, PsycInfo, the NIDA research monograph index and the reference list of clinicaltrials.gov) was conducted for the period from January 1985 to October 2009. There were no restrictions on the identification or inclusion of studies in terms of publication status, language and design type. A variety of medications have failed to show efficacy in clinical trials, including a dopamine partial agonist (aripiprazole), GABAergic agents (gabapentin) and serotonergic agents (SSRI, ondansetron, mirtazapine). Three double-blind placebo-controlled trials using modafinil, bupropion and naltrexone have shown positive results in reducing amphetamine or methamphetamine use. Two studies employing agonist replacement medications, one with d-amphetamine and the other with methylphenidate, have also shown promise. Despite the lack of success in most studies to date, increasing efforts are being made to develop medications for the treatment of methamphetamine dependence and several promising agents are targets of further research.

Efficacy of the atypical antipsychotic aripiprazole in d-amphetamine-based preclinical models of mania

The atypical antipsychotic aripiprazole has been demonstrated to reduce symptoms of bipolar mania. To further profile the antimanic-like properties of aripiprazole in relevant preclinical models, we examined its efficacy in d-amphetamine-based behavioural models of acute mania in rats. The effects of acute and repeated administration of aripiprazole were assessed in the facilitation of intracranial self-stimulation (ICSS) and hyperlocomotion after acute d-amphetamine, and in the sensitized facilitation of ICSS function and hyperlocomotion after repeated d-amphetamine. Acutely, aripiprazole (0.75, 1.5 and 2.5 mg/kg i.p.) increased ICSS thresholds, attenuated the reward-facilitating effects of d-amphetamine (0.5 mg/kg i.p.), decreased motor activity and prevented d-amphetamine-induced hyperlocomotion. Co-administration of aripiprazole and d-amphetamine for 7 d resulted in aripiprazole counteracting the d-amphetamine-induced sensitization in facilitation of brain reward function and hyperlocomotion. These results indicate the efficacy of aripiprazole in d-amphetamine-based preclinical models of acute mania that are characterized by increased motivational drive and/or hyperfunction of brain reward.

Neurologic aspects of drug abuse

Neurologic aspects of drug abuse vary. This article explains the general nature of drug abuse, identifies the physiologic effects of certain drugs, and briefly describes the neurobiology of addiction. This article also reviews available treatment options for those addicted to substances of abuse, and clarifies common misconceptions, including the differences between tolerance, abuse, and addiction.

Evaluation of modafinil effects on cardiovascular, subjective, and reinforcing effects of methamphetamine in methamphetamine-dependent volunteers

Methamphetamine is a highly addictive stimulant and long-term exposure leads to reductions in dopamine. One therapeutic strategy is to develop and test compounds that normalize dopamine. The primary aim of this study was to determine the safety of modafinil treatment during methamphetamine exposure in a controlled clinical setting. Methamphetamine-dependent volunteers (N=13), who were not seeking treatment, were randomized to receive either modafinil (200mg, PO) or matching placebo over three days (Days 1-3 or Days 8-10). On Day 1, subjects were randomized to modafinil or placebo in the morning, and then 3 and 6h later received infusions of methamphetamine (0 and 30 mg, i.v.), after which cardiovascular and subjective effects were assessed. On Day 3, participants completed i.v. self-administration sessions during which they made 10 choices for low doses of methamphetamine (3mg, i.v.) or saline. Days 4-7 were used as a washout period. On Day 8 participants were assigned to the alternate study medication (placebo or modafinil), and the same testing procedures were repeated through Day 10. The data reveal that modafinil treatment was well-tolerated and not associated with increased incidence of adverse events. In general, modafinil reduced by approximately 25% ratings of methamphetamine-induced "Any Drug Effect", "High", and "Want Methamphetamine", and reduced total number of choices for methamphetamine and monetary value of methamphetamine, though none of these measures reached statistical significance. Given these encouraging, though non-significant trends, the primary conclusion is that it appears safe to proceed with modafinil in further clinical evaluations of therapeutic efficacy.

Repeated aripiprazole administration attenuates cocaine seeking in a rat model of relapse

RATIONALE

Aripiprazole (Abilify) is an atypical antipsychotic drug characterized by partial agonist activity at dopamine (DA) D(2)/D(3) receptors and a low side-effect profile. While we previously demonstrated that acute aripiprazole blocked the reinstatement of cocaine seeking in an animal model of relapse, clinical treatment of relapse prevention necessitates testing the effects of aripiprazole following prolonged abstinence, as well as after repeated administration during withdrawal from cocaine.

OBJECTIVES

We assessed the effects of repeated aripiprazole treatment on cocaine seeking after abstinence and during conditioned cue-induced and cocaine-primed reinstatement in rats.

MATERIALS AND METHODS

Rats self-administered intravenous cocaine paired with a light + tone stimulus for 10-14 days, followed by 2 weeks of abstinence. Following post-abstinence relapse testing, lever responding was allowed to extinguish, with subsequent reinstatement testing occurring either in the presence of the conditioned stimulus, or after a cocaine-priming injection (10 mg/kg, intraperitoneal (IP)). Following 3 or 7 days of pretreatment, rats received an injection of aripiprazole (0.25, 0.5, and 1.0 mg/kg, IP) or vehicle prior to post-abstinence relapse and reinstatement testing.

RESULTS

Vehicle-pretreated animals showed robust cocaine seeking during relapse and reinstatement testing, an effect that was significantly attenuated by aripiprazole pretreatment, although no lasting effects were found in the absence of acute injection.

DISCUSSION

These findings support the possibility that repeated aripiprazole may be an effective therapeutic agent for the prevention of relapse in abstinent cocaine users. Based on its antipsychotic profile, aripiprazole may be particularly useful for individuals diagnosed with comorbid psychoses, such as schizophrenia or bipolar disorder.

The cardiovascular and subjective effects of methamphetamine combined with gamma-vinyl-gamma-aminobutyric acid (GVG) in non-treatment seeking methamphetamine-dependent volunteers

Gamma-vinyl-gamma-aminobutyric acid (GVG) elevates central nervous system gamma-aminobutyric acid (GABA) levels by irreversibly inhibiting GABA transaminase. An open-label clinical trial in humans suggested that GVG may reduce cocaine and methamphetamine use. To test safety and to obtain preliminary data on efficacy of GVG for treating methamphetamine dependence, we conducted a double-blind, placebo-controlled, parallel group study of GVG interaction with the cardiovascular and subjective effects produced by methamphetamine. Non-treatment seeking methamphetamine-dependent volunteers received either GVG (N=8) or placebo (N=9) by random assignment. GVG treatment was initiated at 1 g/day and increased to 5 g/day. After reaching the target dose of 5 g/day, participants received methamphetamine (15+30 mg, IV), and cardiovascular and subjective effects were assessed. No serious adverse events were noted, and the total number of adverse events was similar between the treatment groups. Considering the full time course and peak effects independently, no significant differences were detected between the groups for systolic or diastolic blood pressures, or heart rate, following methamphetamine exposure. Some methamphetamine-induced cardiovascular changes approached significance (p<0.10) and may warrant attention in future trials. Methamphetamine-induced subjective effects ("any drug effect", "high", "crave methamphetamine") were statistically similar between GVG and placebo treatment groups. Pharmacokinetic data indicate that GVG treatment did not alter methamphetamine or amphetamine plasma levels, and there was no association between methamphetamine or amphetamine plasma levels and peak cardiovascular effects. Taken together, the data indicate that GVG treatment is generally well tolerated but not efficacious in attenuating the positive subjective effects of methamphetamine in the laboratory.