Effects of topiramate on methamphetamine-induced changes in attentional and perceptual-motor skills of cognition in recently abstinent methamphetamine-dependent individuals

Trait anger as a predictor of dangerous driving behaviour amongst people who use methamphetamine

INTRODUCTION

Despite increased prevalence of methamphetamine in road trauma, it remains unclear how its use translates to an increased risk of traffic-related harm. Exploration of psychosocial factors may thus help identify relevant predictors of dangerous driving behaviour among people who regularly consume methamphetamine.

METHODS

Licenced individuals who report predominant and sustained methamphetamine use (at least 1-time/month for 6 months at heaviest use) were recruited from the Australian community and via targeted campaign (Eastern Health). Psychosocial, substance use and driving behaviour data (Dula Dangerous Driving Index, DDDI) were collected via a secure anonymous online forced-entry survey platform (Qualtrics).

RESULTS

Seventy-seven individuals (65.5 % male) aged between 20-50 years [mean = 29.7, ± Standard Deviation (SD) 6.1] were included. Most (90 %) respondents met criteria for problematic methamphetamine use [Severity of Dependency Scale (SDS) score ≥ 5], and 75 % were high-risk alcohol consumers [Alcohol Use Disorders Identification Test (AUDIT-C) score ≥ 4 for men and ≥ 3 for women]. On average, age of first methamphetamine use occurred at 23.3 years (±5.2). A best-possible subset's regression selection method with dangerous driving behaviour as the dependent variable determined the model with three predictors (alcohol use, substance dependence severity and trait anger) as most parsimonious. After controlling for substance use, trait anger strongly and positively predicted dangerous driving behaviour as measured by the DDDI ([F(3,74) = 26.06, p < .001, adjusted R2 = 0.50, Cohens f2 = 0.42).

DISCUSSION AND CONCLUSIONS

Trait anger is a strong predictor of risky driving among road users who use methamphetamine. Interactions between stable negative-emotional and situational traffic and driving-related factors may increase risk of harm through greater engagement in risk-taking behaviour.

Effects of topiramate on morphological and structural alterations of the anterior cingulate cortex in aggressive socially isolated mice

RATIONALE

Topiramate, an approved antiepileptic drug, was found effective in treating aggressive symptoms in humans and rodents. However, the effects and mechanisms of Topiramate on aggressive behavior are still unclear. Our previous study indicated that intraperitoneal administration of Topiramate successfully decreased aggression and reinforced sociability in socially aggressive mice, and increased cFos-expressing neurons in the anterior cingulate cortex (ACC). In addition to its pharmacological properties, previous studies have approved the neuroprotective effects of Topiramate. These suggest a potential effect of Topiramate on ACC's structure and function.

OBJECTIVES AND RESULTS

In the present study, we first investigated the structural characteristics of ACC in the social isolation-induced aggression paradigm. The results showed that hyper-aggressive behavior in socially aggressive mice was associated with several structural alterations in ACC: increased neuron death combined with decreased neuron density, increased damaged neuronal morphology and increased neuroinflammation markers. Based on these observations, we next investigated the potential neuroprotective effect of Topiramate against structural alterations of ACC observed in socially aggressive mice. Results indicated that intraperitoneal administration of Topiramate (30 mg/kg) decreased aggression and enhanced sociability without affecting locomotor activity. Interestingly, the anti-aggressive effect of Topiramate was associated with decreased neuronal death, ameliorated damaged neuronal morphology, and decreased reactive microglia markers in ACC.

CONCLUSIONS

Our results provide insights into the structural alterations of ACC in aggressive socially aggressive mice. Moreover, the present study suggested that the anti-aggressive effect of Topiramate could be related to its neuroprotective effects against the structural alterations of ACC.

Pharmacological treatment for methamphetamine withdrawal: A systematic review and meta-analysis of randomised controlled trials

ISSUES

Cessation of methamphetamine use may result in a characteristic withdrawal syndrome, no medication has been approved for this indication. This systematic review aims to assess the efficacy of pharmacotherapy for methamphetamine withdrawal, the first comprehensive meta-analysis since 2008.

APPROACH

MEDLINE (1966-2020), CINAHL (1982-2020), PsychINFO (1806-2020) and EMBASE (1947-2020) were systematically searched. Studies were included if they were randomised controlled trials (RCT) investigating pharmacological treatments for methamphetamine withdrawal, reviewing outcomes of treatment discontinuation, mental health outcomes, withdrawal symptoms (including craving) and patient safety. The relative risk (RR) and weighted mean difference (MD) were used to meta-analyse dichotomous and continuous data respectively, with 95% confidence intervals. Risk of bias and Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) assessments were conducted.

KEY FINDINGS

Nine RCTs of six medications (n = 242 participants) met inclusion criteria, however, only six trials of four medications (n = 186) could be meta-analysed. Mean sample size across studies was 27 participants, and 88% of participants were male. The quality of evidence in this review varies from low to very low on GRADE assessments. Amineptine may reduce discontinuation rates (RR 0.22, 95% confidence interval [CI] 0.07, 0.72, p = 0.01), and improve global state (MD -0.49, 95% CI -0.80, -0.17), compared with placebo, however, this medication is no longer approved. No other medications improved any domain when compared with placebo. Due to lack of reporting safety profiles could not be established.

CONCLUSIONS

There is insufficient evidence to indicate any medication is effective for the treatment of methamphetamine withdrawal. The poor quality of the evidence indicates a need for better powered, high-quality trials.

Methamphetamine, amphetamine, and aggression in humans: A systematic review of drug administration studies

The relationship between amphetamine use and aggressive or violent behaviour is unclear. This review examined laboratory data collected in humans, who were administered an acute dose of amphetamine or methamphetamine, in order to investigate the link between amphetamines and aggression. It is registered with PROSPERO (CRD42019127711). Included in the analysis are data from twenty-eight studies. Behavioural and/or subjective measures of aggression were assessed in one thousand and sixty-nine research participants, with limited amphetamine-use histories, following a single amphetamine dose (0-35mg). The available published evidence indicates that neither amphetamine nor methamphetamine acutely increased aggression as assessed by traditional laboratory measures. Future research should assess supratherapeutic amphetamine doses as well as include a broader range of multiple aggression measures, facilitating simultaneous assessment of the various components that comprise this complex, multifaceted construct.

Utility of a controlled amphetamine withdrawal paradigm among adults who use methamphetamine: A pilot clinical trial

BACKGROUND

The continued increase in prevalence of methamphetamine use in the United States has resulted in a significant increase in the number of patients entering treatment for methamphetamine use. However, no robustly efficacious pharmacologic treatment for methamphetamine use or withdrawal has been identified to date after stopping methamphetamine use.

AIMS

Given the association between methamphetamine withdrawal and relapse during early treatment, this study tested a controlled d-amphetamine withdrawal paradigm among methamphetamine-using individuals.

METHODS

Treatment-seeking adults who used methamphetamine (N = 34; 47% female; 100% white) were enrolled in a 4-week, randomized, double-blind, placebo-controlled trial in a residential setting, in which all participants were maintained on d-amphetamine (30 mg BID) during week 1, then half were switched to placebo during weeks 2-3. All participants received placebo during week 4. Outcomes included vital signs, withdrawal, cravings for methamphetamine, mood, and cognition. Bivariate analyses tested treatment group differences on baseline demographic and outcome variables. Repeated measures models examined main and interaction effects of treatment over time.

RESULTS/OUTCOMES

Participants were successfully randomized and safely stabilized on d-amphetamine. Craving for methamphetamine increased during weeks 2-3 in the placebo group relative to those on d-amphetamine. Interactions with age and heart rate were noted.

CONCLUSIONS/INTERPRETATION

To our knowledge, this is the first double-blind, placebo-controlled trial measuring pharmacologic effects of abruptly stopping controlled d-amphetamine administration in adults who use methamphetamine. Results support the potential of this withdrawal paradigm to further examine the efficacy of pharmacologic agents in ameliorating methamphetamine withdrawal symptoms.

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.

Use of Topiramate in the Spectrum of Addictive and Eating Disorders: A Systematic Review Comparing Treatment Schemes, Efficacy, and Safety Features

BACKGROUND AND OBJECTIVE

Topiramate has been approved by the US Food and Drug Administration for the treatment of epilepsy since the 1990s, and it has also been used off-label in the treatment of many types of addictive disorders. To date, no systematic review has embraced the entire field of addiction, both substance use and behavioral addictions, including eating disorders, to compare topiramate-based protocols and the related level of evidence in each addictive disorder. Our objective is to fill this gap.

METHODS

A systematic search was conducted using the MEDLINE, PsycINFO, and Cochrane databases without a date or language limit. All trials and meta-analyses assessing the efficacy of topiramate in alcohol use disorder; cocaine use disorder; methamphetamine, nicotine, cannabis, opiate, and benzodiazepine use disorders; binge eating disorder; bulimia; and pathological gambling were analyzed. The quality of the studies was rated using the Cochrane Risk-of-Bias tool for randomized trials (ROB-2), the Risk of Bias In Nonrandomized Studies (ROBINS-I), or the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, depending on the study design. Safety features were assessed based on a wider non-systematic review.

RESULTS

Sixty-two articles were reviewed. Treatment protocols were relatively homogenous across addictive disorders, with slow dose titration schemes and a maximum dose range of 200-400 mg per day. The most supportive evidence for topiramate efficacy was found in alcohol use disorder for drinking reduction parameters only. To a lesser extent, topiramate could be a promising therapeutic option for binge eating disorder and cocaine use disorder. Evidence was weak for other addictive disorders. No major tolerability issues were found, provided that basic safety rules were followed. Adverse drug reactions could lead to early treatment discontinuation.

DISCUSSION

Though off-label, addiction specialists should consider topiramate as a second-line option for drinking reduction in alcohol use disorder, as well as for binge eating disorder or cocaine use disorder.

Possible involvement of CREB/BDNF signaling pathway in neuroprotective effects of topiramate against methylphenidate induced apoptosis, oxidative stress and inflammation in isolated hippocampus of rats: Molecular, biochemical and histological evidences

Chronic abuse of methylphenidate (MPH) can cause serious neurotoxicity. The neuroprotective effects of topiramate (TPM) were approved, but its putative mechanism remains unclear. In current study the role of CREB/BDNF signaling pathway in TPM protection against methylphenidate-induced neurotoxicity in rat hippocampus was evaluated. 60 adult male rats were divided randomly into six groups. Groups received MPH (10mg/kg) only and concurrently with TPM (50mg/kg and 100mg/kg) and TPM (50 and 100mg/kg) only for 14 days. Open field test (OFT) was used to investigate motor activity. Some biomarkers of apoptotic, anti-apoptotic, oxidative, antioxidant and inflammatory factors were also measured in hippocampus. Expression of total (inactive) and phosphorylated (active) CREB and BDNF were also measured in gene and protein levels in dentate gyrus (DG) and CA1 areas of hippocampus. MPH caused significant decreases in motor activity in OFT while TPM (50 and 100mg/kg) inhibited MPH-induced decreases in motor activity. On the other hand, MPH caused remarkable increases in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels in hippocampal tissue. MPH also caused significant decreases of superoxide dismutase, activity and also decreased CREB, in both forms, BDNF and Bcl-2 protein levels. TPM, by the mentioned doses, attenuated these effects and increased superoxide dismutase, glutathione peroxidase and glutathione reductase activities and also increased CREB, in both forms, BDNF and Bcl-2 protein levels and inhibited MPH induced increase in Bax protein level, lipid peroxidation, catalase activity, IL-1β and TNF-α levels. TPM also inhibited MPH induced decreases in cell number and changes in cell shapes in DG and CA1 areas. TPM can probably act as a neuroprotective agent against MPH induced neurotoxicity and this might have been mediated by CREB/BDNF signaling pathway.

Predicting the Abuse Liability of Entactogen-Class, New and Emerging Psychoactive Substances via Preclinical Models of Drug Self-administration

Animal models of drug self-administration are currently the gold standard for making predictions regarding the relative likelihood that a recreational drug substance will lead to continued use and addiction. Such models have been found to have high predictive accuracy and discriminative validity for a number of drug classes including ethanol, nicotine, opioids, and psychostimulants such as cocaine and methamphetamine. Members of the entactogen class of psychostimulants (drugs that produce an "open mind state" including feelings of interpersonal closeness, intimacy and empathy) have been less frequently studied in self-administration models. The prototypical entactogen 3,4-methylenedioxymethamphetamine (MDMA; "Ecstasy") supports self-administration but not with the same consistency nor with the same efficacy as structurally related drugs amphetamine or methamphetamine. Consistent with these observations, MDMA use is more episodic in the majority of those who use it frequently. Nevertheless, substantial numbers of MDMA users will meet the criteria for substance dependence at some point in their use history. This review examines the currently available evidence from rodent self-administration studies of MDMA and two of the new and emerging psychoactive substances (NPS) that produce entactogen type neuropharmacological responses - mephedrone (4-methylmethcathinone; 4MMC; "meow meow") and methylone (3,4-methylenedioxymethcathinone). Overall, the current evidence predicts that these NPS entactogens have enhanced abuse liability compared with MDMA.

Environmental Enrichment Prevents Methamphetamine-Induced Spatial Memory Deficits and Obsessive-Compulsive Behavior in Rats

Objective: This study was designed to examine the effect of environmental enrichment during methamphetamine (METH) dependency and withdrawal on methamphetamine-induced spatial learning and memory deficits and obsessive-compulsive behavior. Method: Adult male Wistar rats (200 ± 10 g) chronically received bi-daily doses of METH (2 mg/kg, sc, with 12 hours intervals) for 14 days. Rats reared in standard (SE) or enriched environment (EE) during the development of dependence on METH and withdrawal. Then, they were tested for spatial learning and memory (the water maze), and obsessive-compulsive behavior as grooming behavior in METH-withdrawn rats. Results: The results revealed that the Sal/EE and METH/EE rats reared in EE spent more time in the target zone on the water maze and displayed significantly increased proximity to the platform compared to their control groups. METH withdrawn rats reared in EE displayed less grooming behavior than METH/SE group. Conclusion: Our findings revealed EE ameliorates METH-induced spatial memory deficits and obsessive-compulsive behavior in rats.

Topiramate impairs cognitive function in methadone-maintained individuals with concurrent cocaine dependence

Topiramate is being investigated as a potential pharmacotherapy for the treatment of addictive disorders. However, its cognitive side effects raise concerns about its use, especially in populations with cognitive impairment, such as persons with chronic substance use disorders. This study investigated topiramate's cognitive effects in individuals dually dependent on cocaine and opioids as part of a double-blind, randomized, controlled trial of topiramate for cocaine dependence treatment. After 5 weeks of stabilization on daily oral methadone (M = 96 mg), participants were randomized to topiramate (n = 18) or placebo (n = 22). Cognitive testing took place at 2 time points: study weeks 4 through 5 to assess baseline performance and 10 to 13 weeks later to assess performance during stable dosing (300 mg topiramate or placebo). All participants were maintained on methadone at both testing times, and testing occurred 2 hours after the daily methadone plus topiramate/placebo administration. The topiramate and placebo groups did not differ on sex, level of education, premorbid intelligence, methadone dose, or illicit drug use. Topiramate slowed psychomotor and information processing speed, worsened divided attention, reduced n-back working memory accuracy, and increased the false alarm rate in recognition memory. Topiramate had no effects on visual processing, other measures of psychomotor function, risk-taking, self-control, Sternberg working memory, free recall, and metamemory. These findings indicate that topiramate may cause cognitive impairment in this population. This effect may limit its acceptability and use as a treatment in individuals with chronic opioid and cocaine use disorders, among whom preexisting cognitive impairments are common. (PsycINFO Database Record

The spatial learning and memory performance in methamphetamine-sensitized and withdrawn rats

OBJECTIVES

There is controversial evidence about the effect of methamphetamine (METH) on spatial memory. We tested the time- dependent effects of METH on spatial short-term (working) and long-term (reference) memory in METH -sensitized and withdrawn rats in the Morris water maze.

MATERIALS AND METHODS

Rats were sensitized to METH (2 mg/kg, daily/5 days, SC). Rats were trained in water maze (4 trials/day/for 5 days). Probe test was performed 24 hr after training. Two days after probe test, working memory training (2 trials/day/for 5 days) was conducted. Acquisition-retention interval was 75 min. The treatment was continued per day 30 and 120 min before the test. Two groups of METH -sensitized rats were trained in reference memory after a longer period of withdrawal (30 days).

RESULTS

Sensitized rats exhibited significantly longer escape latencies on the training, spent significantly less time in the target zone (all, P<0.05), and their working memory impaired 30 min after injection. While, METH has no effect on the spatial learning process 120 min after injection, and rats spent significantly less time in the target zone (P<0.05), as well it has no effect on working memory. Also, impairment of reference memory persisted after prolonged abstinence.

CONCLUSION

Our findings indicated that METH impaired spatial learning and memory 30 min after injection, but spared spatial learning, either acquisition or retention of spatial working, but partially impaired retention of spatial reference memory following 120 min after injection in sensitized rats, which persisted even after prolonged abstinence.

Transcriptome profiling and pathway analysis of genes expressed differentially in participants with or without a positive response to topiramate treatment for methamphetamine addiction

Background

Developing efficacious medications to treat methamphetamine dependence is a global challenge in public health. Topiramate (TPM) is undergoing evaluation for this indication. The molecular mechanisms underlying its effects are largely unknown. Examining the effects of TPM on genome-wide gene expression in methamphetamine addicts is a clinically and scientifically important component of understanding its therapeutic profile.

Methods

In this double-blind, placebo-controlled clinical trial, 140 individuals who met the DSM-IV criteria for methamphetamine dependence were randomized to receive either TPM or placebo, of whom 99 consented to participate in our genome-wide expression study. The RNA samples were collected from whole blood for 50 TPM- and 49 placebo-treated participants at three time points: baseline and the ends of weeks 8 and 12. Genome-wide expression profiles and pathways of the two groups were compared for the responders and non-responders at Weeks 8 and 12. To minimize individual variations, expression of all examined genes at Weeks 8 and 12 were normalized to the values at baseline prior to identification of differentially expressed genes and pathways.

Results

At the single-gene level, we identified 1054, 502, 204, and 404 genes at nominal P values < 0.01 in the responders vs. non-responders at Weeks 8 and 12 for the TPM and placebo groups, respectively. Among them, expression of 159, 38, 2, and 21 genes was still significantly different after Bonferroni corrections for multiple testing. Many of these genes, such as GRINA, PRKACA, PRKCI, SNAP23, and TRAK2, which are involved in glutamate receptor and GABA receptor signaling, are direct targets for TPM. In contrast, no TPM drug targets were identified in the 38 significant genes for the Week 8 placebo group. Pathway analyses based on nominally significant genes revealed 27 enriched pathways shared by the Weeks 8 and 12 TPM groups. These pathways are involved in relevant physiological functions such as neuronal function/synaptic plasticity, signal transduction, cardiovascular function, and inflammation/immune function.

Conclusion

Topiramate treatment of methamphetamine addicts significantly modulates the expression of genes involved in multiple biological processes underlying addiction behavior and other physiological functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-014-0065-x) contains supplementary material, which is available to authorized users.

Pharmacotherapy for stimulant-related disorders

Stimulant-related disorders (SRD) continue to be an important public health problem for which there are presently no approved pharmacotherapies. Although behavioral interventions provide some benefit response varies. The development of novel and effective pharmacotherapies continues to be a research priority. Understanding neural mechanisms critical to the action of stimulants has helped reveal several potential pharmacotherapies that have already shown promise in controlled clinical trials. Common to some of these medications is the ability to reverse neural deficits in individuals with SRD. Results from thoroughly conducted clinical trials continue to broaden our knowledge increasing the possibility of soon developing effective pharmacotherapies for SRD.

Substance use disorders: psychoneuroimmunological mechanisms and new targets for therapy

An estimated 76.4 million people worldwide meet criteria for alcohol use disorders, and 15.3 million meet criteria for drug use disorders. Given the high rates of addiction and the associated health, economic, and social costs, it is essential to develop a thorough understanding of the impact of substance abuse on mental and physical health outcomes and to identify new treatment approaches for substance use disorders (SUDs). Psychoneuroimmunology is a rapidly expanding, multidisciplinary area of research that may be of particular importance to addiction medicine, as its focus is on the dynamic and complex interactions among behavioral factors, the central nervous system, and the endocrine and immune systems (Ader, 2001). This review, therefore, focuses on: 1) the psychoneuroimmunologic effects of SUDs by substance type and use pattern, and 2) the current and future treatment strategies, including barriers that can impede successful recovery outcomes. Evidence-based psychosocial and pharmacotherapeutic treatments are reviewed. Psychological factors and central nervous system correlates that impact treatment adherence and response are discussed. Several novel therapeutic approaches that are currently under investigation are introduced; translational data from animal and human studies is presented, highlighting immunotherapy as a promising new direction for addiction medicine.

Is cognitive functioning impaired in methamphetamine users? A critical review

The prevailing view is that recreational methamphetamine use causes a broad range of severe cognitive deficits, despite the fact that concerns have been raised about interpretations drawn from the published literature. This article addresses an important gap in our knowledge by providing a critical review of findings from recent research investigating the impact of recreational methamphetamine use on human cognition. Included in the discussion are findings from studies that have assessed the acute and long-term effects of methamphetamine on several domains of cognition, including visuospatial perception, attention, inhibition, working memory, long-term memory, and learning. In addition, relevant neuroimaging data are reviewed in an effort to better understand neural mechanisms underlying methamphetamine-related effects on cognitive functioning. In general, the data on acute effects show that methamphetamine improves cognitive performance in selected domains, that is, visuospatial perception, attention, and inhibition. Regarding long-term effects on cognitive performance and brain-imaging measures, statistically significant differences between methamphetamine users and control participants have been observed on a minority of measures. More importantly, however, the clinical significance of these findings may be limited because cognitive functioning overwhelmingly falls within the normal range when compared against normative data. In spite of these observations, there seems to be a propensity to interpret any cognitive and/or brain difference(s) as a clinically significant abnormality. The implications of this situation are multiple, with consequences for scientific research, substance-abuse treatment, and public policy.

Genetic and environmental correlates of topiramate-induced cognitive impairment

Topiramate is an antiepileptic drug that has marked treatment-limiting side effects on specific aspects of cognitive performance in both patients and healthy volunteers. Because these severe side effects occur only in certain individuals, identifying genetic or environmental variables that influence cognitive response would be of great utility in determining whether to administer this drug to a patient. We gave an acute 100 mg oral dose of topiramate to 158 healthy volunteers and measured how the drug changed their performance on a diverse battery of cognitive tests. We found a wide range of responses to topiramate, and we demonstrated that not all tests in the battery were equally affected. There was no correlation between the effect of topiramate and either education level or baseline cognitive performance. Of interest, there was an up to 55-fold variation in the topiramate plasma levels of the participants. Our genome-wide association study (GWAS) of cognitive response did not reveal any genome-wide significant associations; the study was powered to find variants explaining at least 25% of the variation in cognitive response. Combining the results of this GWAS with a retrospective study of cognitive complaints in 290 epilepsy patients who received topiramate as part of their treatment also did not result in a significant association. Our results support the need for additional genetic studies of topiramate that use larger sample sizes.

Repeated co-administrations of alcohol- and methamphetamine-produced anxiogenic effect could be associated with the neurotoxicity in the dentate gyrus

To date, joint use of alcohol (EtOH) and methamphetamine (MA) represents a specific combination of polydrug abuse. Repeated administrations of EtOH, MA, and combined EtOH and MA were assessed for their effects on brain cell toxicity, cell mitosis and anxiety/depression-like behavior. We found that repeated co-administrations of EtOH and MA produced profound anxiogenic effects. Specifically, combined EtOH and MA decreased open arm exploratory responses in the elevated plus maze test. Moreover, combined EtOH and MA significantly decreased immobile responses in the tail suspension test. MA, EtOH, and their combination all reduced the number of NeuN-positive cells in amygdala (Amg), while neither of them altered the number of NeuN-positive cells in striatum (St) or prefrontal cortex (PFC). Combined EtOH and MA decreased the number of NeuN-positive cells in dentate gyrus (DG). EtOH, MA, and combined EtOH and MA all diminished comparable number of GFAP-positive cells in Amg, DG, and St. Neither of these treatment affected the number of GFAP-positive cells in PFC. EtOH, MA, and combined EtOH and MA generated comparable inhibiting effects on cell proliferation in the subventricular zone (SVZ) and DG. These results, taken together, suggest that repeated co-administrations of MA and EtOH may produce an observable anxiogenic effect. This combination-produced anxiogenic effect could be associated with neuronal loss in the dentate gurus. In contrast, such an anxiogenic effect is less likely related to this combination-caused glial toxicity in limbic regions or cell proliferation-inhibiting effect in the SVZ or DG.

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.

Topiramate in the treatment of substance-related disorders: a critical review of the literature

OBJECTIVE

To critically review the literature on topiramate in the treatment of substance-related disorders.

DATA SOURCES

A PubMed search of human studies published in English through January 2009 was conducted using the following search terms: topiramate and substance abuse, topiramate and substance dependence, topiramate and withdrawal, topiramate and alcohol, topiramate and nicotine, topiramate and cocaine, topiramate and opiates, and topiramate and benzodiazepines.

STUDY SELECTION

26 articles were identified and reviewed; these studies examined topiramate in disorders related to alcohol, nicotine, cocaine, methamphetamine, opioids, Ecstasy, and benzodiazepines.

DATA EXTRACTION

Study design, sample size, topiramate dose and duration, and study outcomes were reviewed.

DATA SYNTHESIS

There is compelling evidence for the efficacy of topiramate in the treatment of alcohol dependence. Two trials show trends for topiramate's superiority over oral naltrexone in alcohol dependence, while 1 trial suggests topiramate is inferior to disulfiram. Despite suggestive animal models, evidence for topiramate in treating alcohol withdrawal in humans is slim. Studies of topiramate in nicotine dependence show mixed results. Human laboratory studies that used acute topiramate dosing show that topiramate actually enhances the pleasurable effects of both nicotine and methamphetamine. Evidence for topiramate in the treatment of cocaine dependence is promising, but limited by small sample size. The data on opioids, benzodiazepines, and Ecstasy are sparse.

CONCLUSIONS

Topiramate is efficacious for the treatment of alcohol dependence, but side effects may limit widespread use. While topiramate's unique pharmacodynamic profile offers a promising theoretical rationale for use across multiple substance-related disorders, heterogeneity both across and within these disorders limits topiramate's broad applicability in treating substance-related disorders. Recommendations for future research include exploration of genetic variants for more targeted pharmacotherapies.

Modulation of impulsivity by topiramate: implications for the treatment of alcohol dependence

Topiramate (TP), an anticonvulsant drug, has been widely used in the treatment of disorders characterized by impulsivity symptoms, so it goes to reason that it might be useful in addictive disorders. Recently, TP has been used to treat alcohol dependence, but it is still not known whether the effects of TP on alcohol consumption are related with its action on impulsivity. The aim of this preliminary study was to investigate which dimension of behavioral impulsivity is associated with the effects of TP. A 12-week, double-blind, placebo-controlled pilot study of TP for the treatment of alcohol dependence was conducted. Subjects were men recruited from alcoholism treatment units (TP = 31; placebo = 32). Diagnoses were made using the Structured Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). Behavioral inhibition was assessed using the continuous performance test (CPT) and the stop-signal task. Differential reinforcement for low-rate responding (DRLR) was used to evaluate the delay-discounting dimension. Alcohol craving and alcohol consumption during the study were evaluated. Patients treated with TP presented lower rates of alcohol consumption in the number of drinks per drinking day (P < 0.05) and the number of heavy drinking days (P < 0.001). Scores on alcohol craving scales decreased significantly, and there was more improvement on the continuous performance test (total omissions and total commissions) and on the stop-signal task in the TP group than in the control group. Improved alcohol consumption behavior was associated with performance on the behavioral inhibition paradigm. The results of this study indicate that TP reduces drinking and that the mechanisms underlying this effect may involve, at least in part, modulation of the behavioral inhibition paradigm.

Pharmacotherapy of methamphetamine addiction: an update

Methamphetamine dependence is a serious public health problem worldwide for which there are no approved pharmacological treatments. Psychotherapy is still the mainstay of treatment; however, relapse rates are high. The search for effective pharmacological treatment has intensified in the last decade. This review will highlight progress in pharmacological interventions to treat methamphetamine dependence as well as explore new pharmacological targets. Published data from clinical trials for stimulant addiction were searched using PubMed and summarized, as well as highlights from a recent symposium on methamphetamine pharmacotherapy presented at the ISAM 2006 meeting, including interim analysis data from an ongoing D-amphetamine study in Australia. Early pilot data are encouraging for administering D-amphetamine and methylphenidate as treatment for heavy amphetamine users. Abilify at 15 mg/day dose increased amphetamine use in an outpatient pilot study. Sertraline, ondansetron, baclofen, tyrosine, and imipramine were ineffective in proof-of-concept studies. Development of pharmacotherapy for methamphetamine dependence is still in an early stage. Data suggesting D-amphetamine and methylphenidate as effective pharmacotherapy for methamphetamine addiction will need to be confirmed by larger trials. Preclinical data suggest that use of GVG, CB1 antagonist, and lobeline are also promising therapeutic strategies.

Comparative cognitive effects of levetiracetam and topiramate in intractable epilepsy

AIM

Anti-epileptic drugs (AED) may cause cognitive impairment. Because intractable epilepsy (IE) represents a distinct group, the purpose of the present study was to study the comparative cognitive effects of the two efficacious AED, levetiracetam (LEV) and topiramate (TPM), on IE.

METHODS

This was a non-randomized, blinded cognitive assessment and parallel design. The cognitive effects of LEV and TPM on 79 demographically comparable patients with IE were assessed at baseline (T1) and after 1 year of treatment (T2) using the Cognitive Abilities Screening Instrument.

RESULTS

Forty patients took TPM and 39 took LEV. At T1, seizure frequency, number of AED, and epilepsy duration were not significantly different. There were no significant differences in cognition between the two groups at T1 or T2. T2 orientation scores were lower than T1 scores in the TPM group (P < 0.05). In the TPM subgroup with T1 cognitive abnormalities, T2 scores for recent memory improved (P < 0.05).

CONCLUSION

For patients with IE, LEV might preserve cognition, TPM's effects for patients with baseline cognitive abnormalities are worth observation.

Biological treatments for amfetamine dependence : recent progress

Amfetamine abuse has grown into a worldwide epidemic. Methamfetamine, a derivative of amfetamine made from readily accessible chemicals, has plagued the US since the 1960s, with an alarming recent surge in the numbers of those meeting the criteria for amfetamine abuse and dependence. We review this problem using a computerised literature search (PubMed 1964-2007) to summarise knowledge from animal and human studies about treatments for amfetamine dependence, while exploring the potential of pharmacogenetics to help uncover new treatment targets. Several promising therapeutic targets have come from animal models of reward, drug-taking behaviour and withdrawal. Although preclinical and selected clinical results have been promising, clinical studies have yielded inconsistent results. To improve these outcomes, pharmacogenetic studies may be used to identify candidate alleles that predict therapeutic response. Exciting preclinical findings and a steady progression of clinical results offer hope for the development of a treatment for amfetamine dependence.

Kinetic and cardiovascular effects of acute topiramate dosing among non-treatment-seeking, methamphetamine-dependent individuals

Previously, we have shown that orally administered topiramate, a sulfamate-substituted fructopyranose derivative, appears to accentuate rather than diminish some aspects of methamphetamine-induced positive subjective mood and cognitive performance. One possible mechanism by which this might occur would be for topiramate to increase plasma methamphetamine level. Such an effect also would be expected to enhance methamphetamine-induced hemodynamic response. We, therefore, studied -- in the same experiment from which the previous findings originated -- the effects of topiramate on the kinetic profile and hemodynamic response to methamphetamine. In a 27-day inpatient study, 10 methamphetamine-dependent individuals participated in a double-blind, placebo-controlled, cross-over design, with oral doses of topiramate (0, 100, and 200 mg) administered as a pretreatment before intravenous doses of methamphetamine (0, 15, and 30 mg). The 3x3 factorial combination of topiramate and methamphetamine resulted in a sequence of the nine treatments administered to each subject in an order determined by a 9x9 Latin Square design. Methamphetamine alone was associated with prototypical increases in hemodynamic response that were not altered in the presence of topiramate. While there was no significant kinetic interaction between topiramate and methamphetamine, there was a non-significant trend for topiramate to increase plasma methamphetamine level. No significant adverse events were reported. The combination of topiramate and methamphetamine at pharmacologically relevant doses appears to be safe. Larger laboratory studies with chronic dosing regimens are needed to establish whether or not there is a kinetic interaction between topiramate and methamphetamine.