FAAH variant Pro129Thr modulates subjective effects produced by cocaine administration

BACKGROUND AND OBJECTIVES

The endogenous cannabinoid anandamide (AEA), an agonist at type-1 cannabinoid (CB1) receptors, is metabolized by fatty acid amide hydrolase (FAAH). The common variant rs324420 C->A within the FAAH gene on chromosome 1 codes for a missense substitution (Pro129Thr), resulting in decreased FAAH activity and increased endocannabinoid potentiation. This FAAH variant has been linked to alterations in mood and stress reactivity, as well as being independently linked to increased risk for addiction. We hypothesized that cocaine use disordered (CUD) participants with the FAAH Pro129 Thr variant would exhibit a distinct profile of cocaine-induced subjective effects in the laboratory.

METHODS

A total of 70 CUD participants received intravenous doses of saline (placebo, 0 mg) and cocaine (20, 40 mg) in a lab-controlled setting and rated 10 subjective effect measures prior to and following saline and cocaine administration, using a Visual Analog Scale (VAS).

RESULTS

The variant allele was associated with increased cocaine-induced subjective ratings for "Drug Effect," "High," and "Depressed." The prevalence of the variant allele A and the AA genotypes were greater in our CUD group than in the general population (A allele: 47% vs. 34%; AA genotype: 30% vs. 13%; p < .05). Finally, the reported amount and frequency of tobacco and cocaine use was higher in subjects with the AC/AA allele.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

These results add to existing evidence that this variant of the FAAH genotype may be over-represented among those who have CUD, and this over-representation may result from greater subjective responses to cocaine administration. (Am J Addict 2018;27:567-573).

Guanfacine Attenuates Adverse Effects of Dronabinol (THC) on Working Memory in Adolescent-Onset Heavy Cannabis Users: A Pilot Study

The cannabinoid-1 receptor (CB1R) agonist Δ9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, adversely effects working memory performance in humans. The α2A-adrenoceptor (AR) agonist guanfacine improves working memory performance in humans. The authors aimed to determine the effects of short-term (6 days) treatment with guanfacine on adverse cognitive effects produced by THC. Employing a double-blind, placebo-controlled crossover design, the cognitive, subjective, and cardiovascular effects produced by oral THC (20 mg) administration were determined twice in the same cannabis users: once after treatment with placebo and once after treatment with guanfacine (3 mg/day). Compared with performance at baseline, THC negatively affected accuracy on spatial working memory trials while participants were maintained on placebo (p=0.012) but not guanfacine (p=0.497); compared with placebo, accuracy was significantly (p=0.003, Cohen's d=-0.640) improved while individuals were treated with guanfacine. Similarly, compared with baseline, THC increased omission errors on an attentional task while participants were maintained on placebo (p=0.017) but not on guanfacine (p=0.709); compared with placebo, there were significantly (p=0.034, Cohen's d=0.838) fewer omissions while individuals were maintained on guanfacine. Although THC increased visual analog scores of subjective effects and heart rate, these increases were similar during treatment with placebo and guanfacine. THC did not significantly affect performance of a recognition memory task or blood pressure while individuals were maintained on either treatment. Although preliminary, these results suggest that guanfacine warrants further testing as a potential treatment for cannabis-induced cognitive deficits.

Comparison of three measurement models of discounting among individuals with methamphetamine use disorder

BACKGROUND AND OBJECTIVES

Delay discounting is associated with numerous clinically significant aspects of substance use disorders (SUDs). Recent studies have demonstrated that different models for assessing discounting may result in disparate conclusions. The current study compared two discounting tasks: money now versus money later (M-M) and methamphetamine now versus money later (MA-M) among non-treatment seeking individuals (N = 59) with methamphetamine use disorder (MAUD). Results from each task were assessed using three different models for assessing delay discounting.

METHODS

Discounting data were fit to three models of discounting, log k using Mazur's hyperbolic formula, area under the curve (AUC), and an alternative AUC model in which the delay values have been log transformed (AUClog).

RESULTS

For both discounting tasks, the distribution of model-related outcomes were normally distributed when using log k and AUClog, but skewed for AUC. Discounting in the MA-M task was significantly greater compared to the M-M task when using log k and AUClog but not AUC.

CONCLUSION

To our knowledge, the current study is the first to report significantly greater discounting in a MA-M relative to M-M discounting task among individuals with MAUD, an outcome consistent with other psychomotor stimulants and drugs of abuse.

SCIENTIFIC SIGNIFICANCE

The differential results observed across the three discounting models reaffirm potential issues with AUC noted in recent studies and highlight that researchers must be cautious when deciding on their final model of discounting. (Am J Addict 2018;XX:1-8).

Exenatide once weekly for smoking cessation: study protocol for a randomized clinical trial

BACKGROUND

Cigarette smoking is the greatest preventable cause of morbidity and premature mortality in the United States. Approved pharmacological treatments for smoking cessation are marginally effective, underscoring the need for improved pharmacotherapies. A novel approach might use glucagon-like peptide-1 (GLP-1) agonists, which reduce alcohol and drug use in preclinical studies. GLP-1 is produced in the intestinal L-cells and in the hindbrain. The peptide maintains glucose homeostasis and reduces food intake. Several GLP-1 agonists are used clinically to treat type 2 diabetes and obesity, but none have been tested in humans to reduce smoking.

AIMS

We will examine whether extended-release exenatide reduces smoking, craving, and withdrawal symptoms, as well as cue-induced craving for cigarettes.

METHODS

We will enroll prediabetic and/or overweight treatment seeking smokers (n = 90) into a double-blind, placebo-controlled, randomized clinical trial. Participants will be randomized in a 1:1 ratio to receive exenatide or placebo. All participants will receive transdermal nicotine replacement therapy (NRT) and behavioral counseling. Abstinence from smoking (verified via expired CO level of ≤5 ppm), craving (Questionnaire of Smoking Urges score), and withdrawal symptoms (Wisconsin Scale of Withdrawal Symptoms score) will be assessed weekly during 6 weeks of treatment and at 1 and 4 weeks posttreatment. Cue-induced craving for cigarettes will be assessed at baseline and at 3 weeks of treatment following virtual reality exposure.

EXPECTED OUTCOMES

We hypothesize that exenatide will increase the number of participants able to achieve complete smoking abstinence above that achieved via standard NRT and that exenatide will reduce craving and withdrawal symptoms, as well as cue-induced craving for cigarettes.

Genetic moderation of cocaine subjective effects by variation in the TPH1, TPH2, and SLC6A4 serotonin genes

OBJECTIVE

This study investigated variants of tryptophan hydroxylase (TPH)1, TPH2, and SLC6A4 in the moderation of the subjective effects of cocaine.

METHODS

Non-treatment-seeking cocaine-dependent individuals (N=66) were intravenously administered saline and cocaine (40 mg) in a randomized order. Participants self-reported subjective effects of cocaine using a visual analog scale starting before administration of saline or cocaine (-15 min) to up to 20 min after infusion. Self-report ratings on the visual analog scale ranged from 0 (no effect) to 100 (greatest effect). Participants were genotyped for the TPH1 rs1799913, TPH2 rs4290270, and SLC6A4 5-HTTLPR variants. Repeated-measures analysis of covariance was used to examine changes in subjective effect scores over time while controlling for population structure.

RESULTS

Participants carrying the TPH1 rs1799913 A allele reported greater subjective response to cocaine for 'stimulated' and 'access' relative to the CC genotype group. Those carrying the TPH2 rs4290270 A allele reported higher 'good effect' and lower 'depressed' effect relative to the TT genotype group. Those carrying the SLC6A4 5-HTTLPR S' allele reported greater 'desire' and 'access' compared with the L'L' genotype group.

CONCLUSION

These findings indicate that TPH1, TPH2, and SLC6A4 variants moderate the subjective effects of cocaine in non-treatment-seeking cocaine-dependent participants.

The limited impact that cocaine use patterns have on neurocognitive functioning in individuals with cocaine use disorder

It is well-documented in the literature that cocaine use is associated with neurocognitive impairment. The manner in which patterns of cocaine use, such as years of use, recent use over the past month, and daily amount of cocaine use, moderate neurocognition has been studied in a relatively piecemeal manner. Hence, the purpose of the study was to evaluate whether cocaine use patterns modulate neurocognition in individuals with cocaine use disorder. Cocaine users who were cocaine-negative ( n=125) were divided into tertiles based on cocaine use patterns and the performances of the highest and lowest groups were compared on the following cognitive measures: Continuous Performance Task-II, n-back, and Hopkins Verbal Learning Task-Revised. Participants with cocaine use disorder who used for more years (25.2±0.6 versus 10.1±0.6 years; mean±standard error of the mean) and who had more recent cocaine use over the past month (26.3±0.5 versus 6.0±0.6 days) did not differ significantly on any of the neurocognitive variables when compared to those with use patterns of shorter duration and less frequency (all p's >0.05). Lastly, participants reporting the greatest amount daily cocaine use (1.8±0.0 g) demonstrated better performance on an auditory working memory task when compared to those with the lowest daily use (0.7±0.0 g; p=0.04). While one might expect that individuals who used greater amounts of cocaine over longer periods of time would demonstrate relatively poorer performance on measures of neurocognition, particularly in the initial phase of abstinence, our findings did not confirm this. While speculative, a potential explanation for these findings is that after an individual uses cocaine for a certain number of years, or uses a specific amount over time, then the deleterious effects of cocaine on neurocognition stabilizes, and increased duration of cocaine use does not further exacerbate those impairments.

The relationship between premorbid IQ and neurocognitive functioning in individuals with cocaine use disorders

OBJECTIVE

To determine whether premorbid IQ mediates performance on neurocognitive tests in individuals diagnosed with cocaine use disorder (CUD).

METHOD

Recently abstinent cocaine users (N = 113) completed measures sensitive to the effects of cocaine on cognition: Conners' Continuous Performance Task-II (CPT-II), n-back working memory test, and Hopkins Verbal Learning Task-Revised (HVLT-R). Premorbid IQ was calculated using the Oklahoma Premorbid Intelligence Estimate, which integrates scores from the Wechsler Adult Intelligence Scale-III and demographic variables. Participants were grouped according to their premorbid IQ using commonly accepted classifications of ability level (above average [>110], average [90-109], and below average [<90]) and comparisons in neurocognitive performance were performed using one-way analysis of variance.

RESULTS

Significant differences were detected between groups on the HVLT-R including Trial 1 (p = .002), total word recall across the 3 list-learning trials (p < .001), and recall following a delay (p < .001). Significant differences were also detected on the N-back, including auditory and visual accuracy (p = .022 and p < .001, respectively) and mean and maximum block length (p < .001). Although significant differences were observed between the above average and average groups (mean effect size = .418 [Cohen's d]), the magnitude of group differences was greatest between the average and below average groups (mean effect size = .716).

CONCLUSIONS

These results raise questions as to whether the neurocognitive impairment observed in individuals diagnosed with CUD predated the onset of cocaine use or whether the impairments were caused by cocaine use. Because these impairments are potential risk factors for poor treatment outcomes, it is important to consider the need to modify treatment programs to account for lower premorbid IQ. (PsycINFO Database Record

Treadmill exercise improves fitness and reduces craving and use of cocaine in individuals with concurrent cocaine and tobacco-use disorder

Exercise may be a useful treatment for substance use disorders. Participants (N=24) included treatment-seeking individuals with concurrent cocaine and tobacco-use disorder (cigarette smokers). Participants were randomized to either running or walking (30min per session, 3 times per week) or sitting (control condition) for 4 consecutive weeks. Several metrics indicated significant differences among runners, walkers, and sitters during sessions, including mean distance covered and calories burned. In addition, remote physiological monitoring showed that the groups differed significantly according to mean maximum heart rate (HR), respiration, and locomotor activity. Across the 4-week study, exercise improved fitness measures including significantly decreasing resting HR. Though not statistically significant, exercise improved abstinence from cocaine and increased self-reports of no cocaine use in last 24h. In general, reductions in tobacco use and craving were not as robust. To our knowledge, this is the first study to evaluate the effects of a multi-week exercise program in individuals with concurrent cocaine and tobacco-use disorder. The data clearly show significant improvements in basic fitness measures and several indices reveal that exercise improved both self-report and biochemically verified reports of cocaine abstinence. Taken together, the data from this study provide preliminary evidence for the efficacy of exercise for improving fitness and reducing cocaine use.

Cocaine cardiovascular effects and pharmacokinetics after treatment with the acetylcholinesterase inhibitor donepezil

BACKGROUND

In rodents, cholinesterase inhibitors can cause sustained decreases in the reinforcing effects of cocaine. Nonetheless, cocaine is metabolized by butyrylcholinesterase (BuChE), raising concerns that cholinesterase inhibition could increase its peripheral concentrations, perhaps augmenting toxicity. Although donepezil is approved for use in patients and selective for inhibiting acetylcholinesterase over BuChE, no studies have reported cocaine bioavailability in human subjects receiving donepezil.

METHODS

Twelve cocaine-dependent veterans received three days of treatment with either oral placebo or 5 mg daily of donepezil, followed by cross-over to the opposite treatment. During both oral treatments, double-blind intravenous cocaine was administered at .0, .18, and .36 mg/kg in a laboratory setting, followed by determinations of heart rate, blood pressure, and plasma concentrations of cocaine and major metabolites.

RESULTS

Intravenous cocaine produced dose-related increases in systolic blood pressure that were most pronounced over the initial 30 minutes after treatment. Oral donepezil attenuated drug-induced elevations of systolic blood pressure following low-dose cocaine (.18 mg/kg). No significant difference in blood pressure following treatment with placebo or donepezil after high-dose cocaine (.36 mg/kg). Peak values of blood pressure and heart rate were unaffected by donepezil. Plasma concentrations of cocaine and metabolites did not differ in donepezil- and placebo-treated participants.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

We conclude that donepezil can attenuate drug-induced increases in systolic blood pressure following low-dose cocaine, but does not otherwise modify the cardiovascular effects of intravenous cocaine. Clinically significant changes in cocaine bioavailability and cardiovascular effects do not occur following this dose of donepezil. (Am J Addict 2016;25:392-399).

Doxazosin XL reduces symptoms of posttraumatic stress disorder in veterans with PTSD: a pilot clinical trial

BACKGROUND

Serotonin and norepinephrine reuptake inhibitors are effective first-line agents for the treatment of posttraumatic stress disorder (PTSD), but treatment is associated with a range of side effects that limit treatment adherence. Prazosin, an α1-noradrenergic antagonist with a half-life of roughly 2-3 hours, has shown promise in the treatment of sleep disturbance and nightmares. Doxazosin extended release (XL) is also an α1-noradrenergic antagonist but with a half-life of approximately 15-19 hours.

METHODS

We conducted a double-blind, placebo-controlled, within-subjects trial to characterize the impact of doxazosin XL on PTSD symptoms. Participants (N = 8) were diagnosed using DSM-IV criteria. They completed the study twice, once during treatment with doxazosin XL and once during treatment with matched placebo, with a 2-week washout separating the 2 episodes. Doxazosin XL was titrated from 4 mg/d to 16 mg/d over 12 days. After 4 days of treatment at 16 mg/d or the equivalent number of placebo capsules, PTSD symptoms were assessed using the Clinician-Administered PTSD Scale (CAPS17) and the PTSD Checklist-Military version (PCL-M). Repeated measures analysis of variance were used to evaluate effects of treatment, time, and treatment × time. This study was run from November 20, 2013, to June 31, 2014.

RESULTS

Doxazosin XL treatment was associated with a nonsignificant treatment × time reduction in ratings on the CAPS hyperarousal subscale (P < .10) (but not on the CAPS Total score) and with significant treatment × time reductions in PCL-M ratings (P = .002).

CONCLUSIONS

Doxazosin XL may be an effective alternative to prazosin for the treatment of some PTSD symptoms.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier:NCT02308202.

Subjective and Cardiovascular Effects of Intravenous Methamphetamine during Perindopril Maintenance: A Randomized, Double-Blind, Placebo-Controlled Human Laboratory Study

BACKGROUND

Our pilot study suggested that the angiotensin-converting enzyme inhibitor perindopril might reduce some subjective effects produced by i.v. methamphetamine. We characterized the impact of a wider range of perindopril doses on methamphetamine-induced effects in a larger group of non-treatment-seeking, methamphetamine-using volunteers.

METHODS

Before treatment, participants received 30mg methamphetamine. After 5 to 7 days of perindopril treatment (0, 4, 8, or 16mg/d), participants received 15 and 30mg of methamphetamine on alternate days. Before and after treatment, participants rated subjective effects and cardiovascular measures were collected.

RESULTS

Prior to treatment with perindopril, there were no significant differences between treatment groups on maximum or peak subjective ratings or on peak cardiovascular effects. Following perindopril treatment, there were significant main effects of treatment on peak subjective ratings of "anxious" and "stimulated"; compared to placebo treatment, treatment with 8mg perindopril significantly reduced peak ratings of both anxious (P=.0009) and stimulated (P=.0070). There were no significant posttreatment differences between groups on peak cardiovascular effects.

CONCLUSIONS

Moderate doses of perindopril (8mg) significantly reduced peak subjective ratings of anxious and stimulated as well as attenuated many other subjective effects produced by methamphetamine, likely by inhibiting angiotensin II synthesis. Angiotensin II is known to facilitate the effects of norepinephrine, which contributes to methamphetamine's subjective effects. The lack of a classic dose-response function likely results from either nonspecific effects of perindopril or from between-group differences that were not accounted for in the current study (i.e., genetic variations and/or caffeine use). The current findings suggest that while angiotensin-converting enzyme inhibitors can reduce some effects produced by methamphetamine, more consistent treatment effects might be achieved by targeting components of the renin-angiotensin system that are downstream of angiotensin-converting enzyme.

Dopamine D3 receptor-preferring agonist enhances the subjective effects of cocaine in humans

Pramipexole is a D3 dopamine receptor-preferring agonist indicated for the treatment of Parkinson disease. Studies associate pramipexole with pathological gambling and impulse control disorders suggesting a role for D3 receptors in reinforcement processes. Clinical studies showed pramipexole decreased cocaine craving and reversed central deficits in individuals with cocaine use disorder. Preclinical studies have shown acute administration of pramipexole increases cocaine's reinforcing effects whereas other reports suggest chronic pramipexole produces tolerance to cocaine. In a randomized, double-blind, placebo-controlled study we examined the impact of pramipexole treatment on the subjective effects produced by cocaine in volunteers with cocaine use disorder. Volunteers received pramipexole titrated up to 3.0mg/d or placebo over 15 days. Participants then received intravenous cocaine (0, 20 and 40mg) on day 15. Cardiovascular and subjective effects were obtained with visual analog scales at time points across the session. Pramipexole alone increased peak heart rate following saline and diastolic blood pressure following cocaine. Pramipexole produced upwards of two-fold increases in positive subjective effects ratings following cocaine. These results indicate that chronic D3 receptor activation increases the subjective effects of cocaine in humans. Caution should be used when prescribing pramipexole to patients that may also use cocaine.

Next Generation Programmable Bio-Nano-Chip System for On-Site Detection in Oral Fluids

Current on-site drug of abuse detection methods involve invasive sampling of blood and urine specimens, or collection of oral fluid, followed by qualitative screening tests using immunochromatographic cartridges. Test confirmation and quantitative assessment of a presumptive positive are then provided by remote laboratories, an inefficient and costly process decoupled from the initial sampling. Recently, a new noninvasive oral fluid sampling approach that is integrated with the chip-based Programmable Bio-Nano-Chip (p-BNC) platform has been developed for the rapid (~ 10 minutes), sensitive detection (~ ng/ml) and quantitation of 12 drugs of abuse. Furthermore, the system can provide the time-course of select drug and metabolite profiles in oral fluids. For cocaine, we observed three slope components were correlated with cocaine-induced impairment using this chip-based p-BNC detection modality. Thus, this p-BNC has significant potential for roadside drug testing by law enforcement officers. Initial work reported on chip-based drug detection was completed using 'macro' or "chip in the lab" prototypes, that included metal encased "flow cells", external peristaltic pumps and a bench-top analyzer system instrumentation. We now describe the next generation miniaturized analyzer instrumentation along with customized disposables and sampling devices. These tools will offer real-time oral fluid drug monitoring capabilities, to be used for roadside drug testing as well as testing in clinical settings as a non-invasive, quantitative, accurate and sensitive tool to verify patient adherence to treatment.

Safety and Preliminary Efficacy of the Acetylcholinesterase Inhibitor Huperzine A as a Treatment for Cocaine Use Disorder

BACKGROUND

Cholinergic transmission is altered by drugs of abuse and contributes to psychostimulant reinforcement. In particular, acetylcholinesterase inhibitors, like huperzine A, may be effective as treatments for cocaine use disorder.

METHODS

The current report describes results from a double-blind, placebo-controlled study in which participants (n=14-17/group) were randomized to huperzine A (0.4 or 0.8 mg) or placebo. Participants received randomized infusions of cocaine (0 and 40 mg, IV) on days 1 and 9. On day 10, participants received noncontingent, randomized infusions of cocaine (0 and 20mg, IV) before making 5 choices to receive additional infusions.

RESULTS

Huperzine A was safe and well-tolerated and compared with placebo, treatment with huperzine A did not cause significant changes in any cocaine pharmacokinetic parameters (all P>.05). Time-course and peak effects analyses show that treatment with 0.4 mg of huperzine A significantly attenuated cocaine-induced increases of "Any Drug Effect," "High," "Stimulated," "Willing to Pay," and "Bad Effects" (all P>.05).

CONCLUSIONS

The current study represents a significant contribution to the addiction field since it serves as the first published report on the safety and potential efficacy of huperzine A as a treatment for cocaine use disorder.

Application of programmable bio-nano-chip system for the quantitative detection of drugs of abuse in oral fluids

OBJECTIVE

There is currently a gap in on-site drug of abuse monitoring. Current detection methods involve invasive sampling of blood and urine specimens, or collection of oral fluid, followed by qualitative screening tests using immunochromatographic cartridges. While remote laboratories then may provide confirmation and quantitative assessment of a presumptive positive, this instrumentation is expensive and decoupled from the initial sampling making the current drug-screening program inefficient and costly. The authors applied a noninvasive oral fluid sampling approach integrated with the in-development chip-based Programmable bio-nano-chip (p-BNC) platform for the detection of drugs of abuse.

METHOD

The p-BNC assay methodology was applied for the detection of tetrahydrocannabinol, morphine, amphetamine, methamphetamine, cocaine, methadone and benzodiazepines, initially using spiked buffered samples and, ultimately, using oral fluid specimen collected from consented volunteers.

RESULTS

Rapid (∼10min), sensitive detection (∼ng/mL) and quantitation of 12 drugs of abuse was demonstrated on the p-BNC platform. Furthermore, the system provided visibility to time-course of select drug and metabolite profiles in oral fluids; for the drug cocaine, three regions of slope were observed that, when combined with concentration measurements from this and prior impairment studies, information about cocaine-induced impairment may be revealed.

CONCLUSIONS

This chip-based p-BNC detection modality has significant potential to be used in the future by law enforcement officers for roadside drug testing and to serve a variety of other settings, including outpatient and inpatient drug rehabilitation centers, emergency rooms, prisons, schools, and in the workplace.

A comparison of impulsivity, depressive symptoms, lifetime stress and sensation seeking in healthy controls versus participants with cocaine or methamphetamine use disorders

Previous research has focused on developing theories of addiction that may explain behavior in cocaine- and methamphetamine-dependent individuals. The primary goal of this report was to compare and contrast the prevalence of self-reported measures of impulsivity, depression, lifetime stress and sensation-seeking in healthy controls versus individuals with cocaine or methamphetamine use disorders. Twenty-nine individuals with cocaine use disorders and 31 individuals with methamphetamine use disorders were matched with 31 healthy control participants on several demographic variables. All participants were administered behavioral questionnaires including the Barrett Impulsiveness Scale (assessing impulsivity), Beck Depression Inventory II (assessing depression), Life Stressor Checklist-Revised (assessing lifetime stress) and the Impulsive Sensation Seeking Scale (assessing sensation-seeking). When compared to healthy controls, individuals with cocaine and methamphetamine use disorders had significantly higher levels of impulsivity and sensation-seeking. In addition, when compared to healthy controls, individuals with cocaine use disorders had significantly higher Beck Depression Inventory II scores, while individuals with methamphetamine use disorders had significantly higher Life Stressor Checklist-Revised scores. The results revealed that there were significantly higher levels of impulsivity, depression and sensation-seeking in cocaine users and significantly higher impulsivity, lifetime stress and sensation-seeking in methamphetamine users when compared to healthy controls.

The relationship between sleep and drug use characteristics in participants with cocaine or methamphetamine use disorders

The goal of this project was to evaluate the relationship between self-reported sleep habits, daytime sleepiness, and drug use variables in individuals with cocaine and methamphetamine (METH) use disorders. Participants with a cocaine or meth use disorder completed questionnaires, including the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and a demographic/drug use form. Participants with a cocaine (N=51) or meth use disorder (N=85) were separated into those with either high or low sleep deficits. In participants with a cocaine use disorder, ANOVA revealed significantly higher ESS scores among those defined as "poor sleepers" (with a PSQI score >5) when compared to those defined as "good sleepers" (with a PSQI score ≤5). In addition, poor sleepers reported using cocaine for more days out of the past 30 when compared to good sleepers. Interestingly, good sleepers reported using more grams of cocaine/day compared to poor sleepers. In participants with a METH use disorder, ANOVA revealed significantly higher ESS scores among poor sleepers when compared to good sleepers. Finally, individuals with a METH use disorder that endorsed elevated daytime sleepiness also had significantly higher PSQI scores when compared to those with normal daytime sleepiness. The results indicate that drug use variables, such as recent and daily use, may affect sleep quality and daytime sleepiness in individuals with stimulant use disorders; however, further investigations (i.e. in cocaine and METH users that do not meet criteria for a cocaine or METH use disorder) must be conducted in order to provide more conclusive evidence of the impact these usage variables may have on these sleep characteristics.

Treatment with modafinil and escitalopram, alone and in combination, on cocaine-induced effects: a randomized, double blind, placebo-controlled human laboratory study

BACKGROUND

Concurrent administration of dopamine and serotonin reuptake inhibitors reduces cocaine self-administration in monkeys. Consonant with this, clinical trials assessing modafinil and selective serotonin reuptake inhibitors alone show some efficacy as potential pharmacotherapies for cocaine dependence. We hypothesized that combining modafinil with escitalopram would attenuate the euphoric effects of cocaine to a greater degree than modafinil alone.

METHODS

In a randomized, double blind, parallel groups design participants received either placebo (0mg/day; n=16), modafinil (200mg/day; n=16), escitalopram (20mg/day; n=17), or modafinil+escitalopram (200+20mg/day; n=15) for 5 days. On day 5, during separate sessions participants received an intravenous sample of cocaine (0 or 20mg; randomized) and five $1 bills. Participants rated the subjective effects of the infusions and subsequently made choices to either return $1 and receive another infusion or keep $1 and receive no infusion.

RESULTS

Compared to saline, cocaine (20mg) significantly (p≤0.008) increased most ratings, including "good effects", "stimulated", and "high". Relative to placebo, modafinil significantly (p≤0.007) attenuated subject-rated increases of "any drug effect", "high", "good effects", and "stimulated" produced by cocaine. Compared to saline, participants chose cocaine infusions significantly more; however, no treatment significantly reduced choices for cocaine infusions. Escitalopram did not enhance the efficacy of modafinil to reduce any measure.

CONCLUSIONS

Modafinil attenuated many positive subjective effects produced by cocaine; however, escitalopram combined with modafinil did not enhance the efficacy of modafinil to reduce cocaine effects.

A variant in ANKK1 modulates acute subjective effects of cocaine: a preliminary study

This study aimed to evaluate whether functional variants in the ankyrin repeat and kinase domain-containing 1 (ANKK1) gene and/or the dopamine receptor D2 (DRD2) gene modulate the subjective effects (reward or non-reward response to a stimulus) produced by cocaine administration. Cocaine-dependent participants (N = 47) were administered 40 mg of cocaine or placebo at time 0, and a subjective effects questionnaire (visual analog scale) was administered 15 min prior to cocaine administration, and at 5, 10, 15 and 20 min following administration. The influence of polymorphisms in the ANKK1 and DRD2 genes on subjective experience of cocaine in the laboratory was tested. Participants with a T allele of ANKK1 rs1800497 experienced greater subjective 'high' (P = 0.00006), 'any drug effect' (P = 0.0003) and 'like' (P = 0.0004) relative to the CC genotype group. Although the variant in the DRD2 gene was shown to be associated with subjective effects, linkage disequilibrium analysis revealed that this association was driven by the ANKK1 rs1800497 variant. A participant's ANKK1 genotype may identify individuals who are likely to experience greater positive subjective effects following cocaine exposure, including greater 'high' and 'like', and these individuals may have increased vulnerability to continue using cocaine or they may be at greater risk to relapse during periods of abstinence. However, these results are preliminary and replication is necessary to confirm these findings.

Effects of methamphetamine on the noradrenergic activity biomarker salivary alpha-amylase

BACKGROUND

Methamphetamine (METH) potently activates the sympathetic nervous system (SNS) by increasing central and peripheral norepinephrine (NE). Salivary α-amylase (sAA) is a biomarker of SNS activation that correlates with plasma NE levels. The purpose of this study was to determine the impact of METH on sAA activity and whether changes in sAA activity were correlated with subjective effects ratings.

METHODS

Non-treatment seeking METH-dependent volunteers (N=8) participated in this within-subjects laboratory-based study. Volunteers received randomly administered intravenous METH (0mg, 30 mg) and sAA activity, cardiovascular measures and subjective ratings were assessed at baseline (-15 min) and five post-METH time points (10, 20, 30, 45, and 60 min).

RESULTS

METH (30 mg) increased sAA activity over time. sAA activity significantly correlated with diastolic blood pressure following 0mg METH and systolic blood pressure following 30 mg METH. Subjective ratings (ANY EFFECT, HIGH, GOOD, STIMULATED, LIKE, WLLING TO PAY) highly correlated with sAA over five post-METH time points (N=40; r's=0.543-0.684, p's<0.001). Age, body mass index and METH amount received on a mg/kg basis were significantly associated with sAA activity. Multiple linear regression analysis indicated sAA activity remained a significant predictor of subjective ratings following METH after controlling for these factors.

CONCLUSIONS

The NE peripheral biomarker sAA activity is associated with METH's subjective effects.

The impact of self-reported life stress on current impulsivity in cocaine dependent adults

Current cocaine treatments may be enhanced with a better understanding of the underlying mechanisms that contribute to the onset and maintenance of the disease, such as life stress and impulsivity. Life stress and impulsivity have previously been studied independently as contributors to drug use, and the current study expands upon past research by examining how these factors interact with one another. The aim of the current study was to evaluate the role of life stress in predicting impulsivity in a non-treatment seeking cocaine-dependent sample (N=112). Analyses revealed that trait impulsivity (as measured by the Barratt Impulsiveness Scale) was associated with education (r=-3.09, p<0.01), as those who had higher educational attainment also reported lower rates of trait impulsivity. In addition, those over the age of 30 demonstrated lower impulsivity in decision-making (as measured by delay discounting) than those under 30 (t=2.21, p=0.03). Overall exposure to life stress was not significantly correlated to either aspect of impulsivity. However several specific life stressors were significantly related to greater impulsivity including having been put up for adoption or in foster care (t=-2.96, p<0.01), and having a child taken away against their will (t=-2.68, p=0.01). These findings suggest that age and education relate to impulsivity; and that while an overall compilation of life stress scores was not related to impulsivity, specific types of stress related to either being taken away from a parent or having a child taken away were. Future studies should assess these constructs longitudinally to restrict response bias.

Pharmacotherapeutics for substance-use disorders: a focus on dopaminergic medications

INTRODUCTION

Illicit substance-use is a substantial public health concern, contributing over $150 billion in costs annually to Americans. A complex disease, a substance-use disorder affects neural circuits involved in reinforcement, motivation, learning and memory, and inhibitory control.

AREAS COVERED

The modulatory influence of dopamine in mesocorticolimbic circuits contributes to encoding the primary reinforcing effects of substances and numerous studies suggest that aberrant signaling within these circuits contributes to the development of a substance-use disorder in some individuals. Decades of research focused on the clinical development of medications that directly target dopamine receptors has led to recent studies of agonist-like dopaminergic treatments for stimulant-use disorders and, more recently, cannabis-use disorder. Human studies evaluating the efficacy of dopaminergic agonist-like medications to reduce reinforcing effects and substance-use provide some insight into the design of future pharmacotherapy trials. A search of PubMed using specific brain regions, medications, and/or the terms 'dopamine', 'cognition', 'reinforcement', 'cocaine', 'methamphetamine', 'amphetamine', 'cannabis', 'treatment/pharmacotherapy', 'addiction/abuse/dependence' identified articles relevant to this review.

EXPERT OPINION

Conceptualization of substance-use disorders and their treatment continues to evolve. Current efforts increasingly focus on a strategy fostering combination pharmacotherapies that target multiple neurotransmitter systems.

The relationship between lifetime stress and addiction severity in cocaine-dependent participants

OBJECTIVE

The primary focus of the current report was to determine if there was an association between LSC-R and ASI-Lite scores in cocaine-dependent individuals. The secondary focus was to determine if any demographic/drug use variables or comorbid psychiatric diagnoses (e.g. alcohol-dependence, mood disorders) were associated with higher LSC-R or ASI-Lite scores. We hypothesized that scores on the LSC-R would be positively correlated with ASI-Lite scores.

METHOD

The sample included 239 cocaine-dependent individuals. The primary assessments administered were the LSC-R, the ASI-Lite, and the demographic/drug use questionnaire.

RESULTS

Simple linear regression revealed that total lifetime stress was positively and significantly correlated with total ASI-Lite scores; however, the r(2) value was very low indicating that this relationship is more likely explained by other factors. It was also determined that participants with a diagnosis of alcohol dependence versus those that did not had significantly higher ASI-Lite scores (even when the alcohol composite score was included as a covariate). Participants with a diagnosis of a mood disorder versus those who did not had significantly higher LSC-R scores and females had significantly higher LSC-R scores when compared to males. After performing a median split, those cocaine users with High LSC scores had significantly higher Beck Depression Inventory-II scores, total ASI-Lite scores, and Fagerström Test of Nicotine Dependence scores when compared to those individuals with Low LSC scores. Further analysis of the ASI-Lite demonstrated that composite scores in the domains of Medical, Drug, Legal, Family and Social Status, and Psychiatric were all significantly elevated in the High LSC group.

CONCLUSIONS

Overall, those with higher lifetime stress demonstrated higher addiction severity and depressive symptoms versus those that endorsed lower lifetime stress. Thus, additional research should be conducted investigating the impact stressful life events has on drug use patterns and characteristics.

The influence of smoking cigarettes on the high and desire for cocaine among active cocaine users

The primary aim was to evaluate whether nicotine use alters the high or desire for cocaine among active cocaine users who concurrently smoke cigarettes. Participants answered the Fagerstrom Test for Nicotine Dependence (FTND), Nicotine-Stimulant Interaction Questionnaire (NSIQ), and Multiple Drug Use Questionnaire (MDUQ). These questionnaires employ subject recall of participants' drug use habits. The participants that smoked (N=163/188) were primarily African American males who were 45.0±0.5 (mean±S.E.M.) years of age, and used cocaine for 17.9±0.6 years and 19.8±0.6 days out of the last 30. These individuals smoked 14.0±0.8 cigarettes/day (CPD), scored 4.6±0.2 (on a scale of 0-10) on the FTND, and smoked cigarettes for 23.5±0.7 years. Two questions from the MDUQ, which evaluates the interaction between cocaine and nicotine, (-5: reduces effect, 0: no change, +5: increases effect) included "Does nicotine affect the high that you experience from cocaine?" and "Does nicotine affect your desire for cocaine?", and the scores were 1.3±0.2 and 0.8±0.2, respectively. The NSIQ also evaluated interactive effects of nicotine and cocaine, on a scale of 0 to 100 (0: not at all, 100: most ever). Smokers responded most strongly that using cocaine increased both the urge to smoke and cigarette craving. Additional analyses were performed by separating participants into HighCPD vs. LowCPD groups via median split. The HighCPD group smoked 22.7±1.1 CPD while the LowCPD group smoked 6.4±0.3 CPD [F(1,161)=228.4, p<0.0001], and the HighCPD group had a mean FTND score twice that of the LowCPD group. Significant differences emerged between the two groups on multiple items of the NSIQ, but not the MDUQ. The subjective ratings of high and desire for cocaine, and several subjective effects produced by cocaine, were modestly altered by cigarette smoking. Taken together, these data suggest that cigarette smoking may augment the craving and high produced by cocaine.

Effects of D-cycloserine on cue-induced craving and cigarette smoking among concurrent cocaine- and nicotine-dependent volunteers

Rates of cigarette smoking are 3- to 4-fold greater among those with cocaine-dependence, and compared to non-users, cocaine users are at greater risk of incurring smoking-related negative health effects and death. The current study examined D-cycloserine's (0 or 50mg once weekly) effects on 1) extinction of cue-induced craving for cigarettes, 2) cigarette smoking in conjunction with cognitive-behavioral therapy, and 3) safety and tolerability in cocaine-dependent smokers. This was a double-blind, placebo-controlled, between groups, outpatient study. Participants (N=29) were concurrent cocaine- and nicotine-dependent volunteers seeking treatment for their cigarette smoking. Study visits were 3 times per week for 4 consecutive weeks. At each visit, participants received cognitive-behavioral therapy for smoking, were exposed to smoking cues. A subset of participants (N=22) returned for 6-month follow-up visits. While craving decreased, no significant effects of D-cycloserine treatment were observed. Likewise, significant decreases in smoking were observed at study days 6 (p<0.002) and 12 (p<0.0001) relative to baseline, although no participants achieved complete abstinence. However, there was no effect of D-cycloserine on cigarette smoking during treatment or at 6-mos follow-up. The treatment was safe and tolerable, with nearly 90% of treatment sessions attended based on an intent-to-treat analysis. While no effects of D-cycloserine on craving or smoking were observed in the current study, the results do suggest that smoking treatment is well accepted and may be effective for cocaine-dependent individuals.

The impact of disulfiram treatment on the reinforcing effects of cocaine: a randomized clinical trial

Background

Clinical trials indicate that disulfiram (250 mg/d) reduces cocaine use, though one study found that treatment with lower doses of disulfiram (62.5 and 125 mg/d) increased cocaine use. We conducted the present study to better understand how disulfiram alters the reinforcing effects of cocaine in cocaine users.

Methods

Seventeen non-treatment seeking, cocaine-dependent volunteers participated in this double-blind, placebo-controlled, laboratory-based study. A cross-over design was utilized in which participants received placebo in one phase and disulfiram (250 mg/d) in the other. Following three days of study medication participants completed two choice sessions. In one they made 10 choices between receiving an intravenous infusion of saline or money that increased in value (US$ 0.05–16) and in the other cocaine (20 mg) or money.

Results

Participants chose cocaine more than saline under both disulfiram and placebo conditions (p<0.05). Unexpectedly, disulfiram increased both the number of cocaine and saline infusion choices (p<0.05). We next examined the relationship between disulfiram dose and cocaine choices. Disulfiram dose (mg/kg bodyweight) was negatively correlated with number of choices for cocaine (p<0.05). Disulfiram also enhanced cocaine-induced increases in cardiovascular measures (p's<0.05–0.01).

Conclusions

Disulfiram's impact on the reinforcing effects of cocaine depends on dose relative to body weight. Our results suggest that the use of weight-based medication doses would produce more reliable effects, consistent with weight-based dosing used in pediatrics and in preclinical research.

Trial Registration

Clinicaltrials.gov NCT00729300

Acute modafinil exposure reduces daytime sleepiness in abstinent methamphetamine-dependent volunteers

The purpose of this study was to evaluate the effects of acute, oral modafinil (200 mg) exposure on daytime sleepiness in methamphetamine (Meth)-dependent individuals. Eighteen Meth-dependent subjects were enrolled in a 7-d inpatient study and were administered placebo or modafinil on day 6 and the counter-condition on day 7 (randomized) of the protocol. Subjects completed several subjective daily assessments (such as the Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, Beck Depression Inventory and visual analogue scale) throughout the protocol as well as objective assessments on days 5-7, when the Multiple Sleep Latency Test was performed. The results of the current study suggest that short-term abstinence from Meth is associated with increased daytime sleepiness and that a single dose of 200 mg modafinil reduces daytime somnolence in this population. In addition, a positive correlation was found between subjective reporting of the likelihood of taking a nap and craving and desire for Meth, as well as the likelihood of using Meth and whether Meth would make the participant feel better. The results of this study should be considered when investigating candidate medications for Meth-dependence, especially in those individuals who attribute their Meth use to overcoming deficits resulting from sleep abnormalities.

d-Cycloserine administration does not affect neurocognition in concurrent cocaine- and nicotine-dependent volunteers

Neurocognitive impairment is a well-documented consequence of long-term, repeated cocaine exposure and has been identified as an important target of treatment. Thus, this study sought to determine whether the N-methyl-d-aspartate (NMDA) partial agonist, d-cycloserine could improve neurocognitive performance in a sample of 27 long-term, high dose cocaine dependent individuals who were not seeking treatment at the time of enrollment in the study. This double-blind, placebo-controlled study evaluated whether a single dose of 0 or 50mg of d-cycloserine would enhance performance on measures of attention/information processing speed, episodic memory, and executive/frontal lobe functioning relative to test performance at baseline. The results revealed that d-cycloserine did not modulate neurocognition in this cohort, though there are a number of factors that may have mitigated the effects of d-cycloserine in this particular study. The negative findings notwithstanding, the current study serves as a springboard for future investigations that will examine whether other medications that can modulate neurocognition in cocaine-dependent study participants.

Noradrenergic α₁ receptor antagonist treatment attenuates positive subjective effects of cocaine in humans: a randomized trial

Background

Preclinical research implicates dopaminergic and noradrenergic mechanisms in mediating the reinforcing effects of drugs of abuse, including cocaine. The objective of this study was to evaluate the impact of treatment with the noradrenergic α₁ receptor antagonist doxazosin on the positive subjective effects of cocaine.

Methods

Thirteen non-treatment seeking, cocaine-dependent volunteers completed this single-site, randomized, placebo-controlled, within-subjects study. In one study phase volunteers received placebo and in the other they received doxazosin, with the order counterbalanced across participants. Study medication was masked by over-encapsulating doxazosin tablets and matched placebo lactose served as the control. Study medication treatment was initiated at 1 mg doxazosin or equivalent number of placebo capsules PO/day and increased every three days by 1 mg. After receiving 4 mg doxazosin or equivalent number of placebo capsules participants received masked doses of 20 and 40 mg cocaine IV in that order with placebo saline randomly interspersed to maintain the blind.

Results

Doxazosin treatment was well tolerated and doxazosin alone produced minimal changes in heart rate and blood pressure. During treatment with placebo, cocaine produced dose-dependent increases in subjective effect ratings of “high”, “stimulated”, “like cocaine”, “desire cocaine”, “any drug effect”, and “likely to use cocaine if had access” (p<.001). Doxazosin treatment significantly attenuated the effects of 20 mg cocaine on ratings of “stimulated”, “like cocaine”, and “likely to use cocaine if had access” (p<.05). There were trends for doxazosin to reduce ratings of “stimulated”, “desire cocaine”, and “likely to use cocaine if had access” (p<.10).

Conclusions

Medications that block noradrenergic α₁ receptors, such as doxazosin, may be useful as treatments for cocaine dependence, and should be evaluated further.

Trial Registration

Clinicaltrials.gov NCT01062945

VIRTUAL REALITY CUE EXPOSURE THERAPY FOR THE TREATMENT OF TOBACCO DEPENDENCE

Researchers and clinicians have recently begun using Virtual Reality (VR) to create immersive and interactive cue exposure paradigms. The current study aimed to assess the effectiveness of individual cue exposure therapy (CET), using smoking-related VR cues (smoking-VR) as a smoking cessation treatment compared to a placebo-VR (neutral cue) treatment. The sample consisted of healthy treatment-seeking cigarette smokers, who underwent bi-weekly cognitive behavioral group therapy (CBT) plus either smoking-VR CET or placebo-VR CET (random assignment). Smoking-VR CET participants had a higher quit rate than placebo-VR CET participants (P = 0.015). Smoking-VR CET treated participants also reported smoking significantly fewer cigarettes per day at the end of treatment than placebo-VR CET treated participants (P = 0.034). These data indicate that smoking-related VR CET may prove useful in enhancing the efficacy of CBT treatment for tobacco dependence.

Acute, low-dose methamphetamine administration improves attention/information processing speed and working memory in methamphetamine-dependent individuals displaying poorer cognitive performance at baseline

Abstinent methamphetamine (Meth) dependent individuals demonstrate poorer performance on tests sensitive to attention/information processing speed, learning and memory, and working memory when compared to non-Meth dependent individuals. The poorer performance on these tests may contribute to the morbidity associated with Meth-dependence. In light of this, we sought to determine the effects of acute, low-dose Meth administration on attention, working memory, and verbal learning and memory in 19 non-treatment seeking, Meth-dependent individuals. Participants were predominantly male (89%), Caucasian (63%), and cigarette smokers (63%). Following a four day, drug-free washout period, participants were given a single-blind intravenous infusion of saline, followed the next day by 30 mg of Meth. A battery of neurocognitive tasks was administered before and after each infusion, and performance on measures of accuracy and reaction time were compared between conditions. While acute Meth exposure did not affect test performance for the entire sample, participants who demonstrated relatively poor performance on these tests at baseline, identified using a median split on each test, showed significant improvement on measures of attention/information processing speed and working memory when administered Meth. Improved performance was seen on the following measures of working memory: choice reaction time task (p≤0.04), a 1-back task (p≤0.01), and a 2-back task (p≤0.04). In addition, those participants demonstrating high neurocognitive performance at baseline experienced similar or decreased performance following Meth exposure. These findings suggest that acute administration of Meth may temporarily improve Meth-associated neurocognitive performance in those individuals experiencing lower cognitive performance at baseline. As a result, stimulants may serve as a successful treatment for improving cognitive functioning in those Meth-dependent individuals experiencing neurocognitive impairment.

Relationship between gender and psychotic symptoms in cocaine-dependent and methamphetamine-dependent participants

BACKGROUND

It has been well documented that cocaine and methamphetamine use can lead to the onset of psychotic symptoms similar to schizophrenia. However, the research and literature on gender differences and stimulant-induced psychosis have been mixed.

OBJECTIVE

The primary aim of this study was to investigate gender differences in the reporting of psychotic symptoms in cocaine- versus methamphetamine-dependent individuals.

METHODS

Participants were recruited from the Los Angeles, California, community via radio and newspaper advertisements. All met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for cocaine or methamphetamine dependence, and all reported either methamphetamine or cocaine as their primary drug of abuse. During a screening interview, participants answered questions from the Psychotic Symptom Assessment Scale, which characterizes various types of psychotic symptoms during drug use ("while high") or during periods of nonuse ("while abstinent").

RESULTS

Participants included 42 cocaine-dependent individuals (27 men, 15 women) and 43 methamphetamine-dependent individuals (25 men, 18 women). Among cocaine users, there were no significant differences between men and women with regard to ethnicity, years of use, route of administration, and amount used in the past week, though they differed significantly with regard to age (P = 0.029). In the "while abstinent" condition, women were significantly more likely than men to report experiencing auditory hallucinations (13% vs 0%, respectively; P = 0.050) and tactile hallucinations (20% vs 0%; P = 0.016), whereas men were more likely to report delusions of grandeur (48% vs 6%; P = 0.006). During the "while high" condition, women were significantly more likely than men to report delusions of grandeur (13% vs 0%, respectively; P = 0.050), tactile hallucinations (33% vs 0%; P = 0.001), and olfactory hallucinations (13% vs 0%; P = 0.050). Among methamphetamine users, there were no significant differences between men and women with regard to age, ethnicity, years of use, route of administration, or amount used in the past week. In the "while abstinent" condition, women were significantly more likely than men to report feeling that something was wrong with the way a part of their body looked (72% vs 32%, respectively; P = 0.009), olfactory hallucinations (39% vs 8%; P = 0.010) and dressing inappropriately (22% vs 0%; P = 0.010). During the "while high" condition, women were more likely than men to report delusions of grandeur (33% vs 16%, respectively; P = 0.030), paranoia (50% vs 16%; P = 0.017), and tactile hallucinations (61% vs 32%; P = 0.050).

CONCLUSIONS

The findings of the present study revealed that cocaine- and methamphetamine-dependent women were more likely than their male counterparts to report experiencing various psychotic symptoms. This information may be useful for clinicians and mental health professionals, who should take these symptoms into account as potential barriers that may impede effective treatment.

The relationship between impulsivity and craving in cocaine- and methamphetamine-dependent volunteers

Impulsivity and craving have been independently hypothesized to contribute to sustained drug use and relapse in addiction. The primary focus of this project was to determine the relationship between impulsivity and craving in 85 cocaine-dependent and 73 methamphetamine-dependent, non-treatment-seeking volunteers. Drug use was assessed with a 14-item, self-report drug and alcohol use questionnaire. Self report instruments utilized included the Barratt Impulsivity Scale (BIS) and the Visual Analog Scale (VAS), which probed "just before your last use of cocaine (for cocaine-dependent participants) or methamphetamine (for methamphetamine-dependent participants), how much craving did you experience?" The groups were similar with respect to recent use of cocaine or methamphetamine, alcohol, nicotine, and marijuana. Analysis of variance (ANOVA) did not reveal significant differences between cocaine and methamphetamine groups for total impulsivity or total craving. Simple linear regression revealed correlations between total impulsivity and total craving in cocaine (r(2)=0.05, p≤0.03) and methamphetamine users (r(2)=0.09, p≤0.008). Participants were separated into high impulsivity (HIBIS) or low impulsivity (LOBIS) subgroups using a median split. ANOVA revealed significantly higher craving in the HIBIS group versus the LOBIS group in methamphetamine users (p≤0.02), but not in cocaine users. For both cocaine and methamphetamine groups, level of impulsivity and craving were found to be related to some drug use variables including years of alcohol use, severity of withdrawal, and craving level following drug use. Taken together, this study shows a marginal relationship between impulsivity and craving, which may further the understanding of motivational factors contributing to ongoing drug use and addiction in psychostimulant users.

Modafinil administration improves working memory in methamphetamine-dependent individuals who demonstrate baseline impairment

Modafinil improves working memory in healthy subjects and individuals diagnosed with schizophrenia and Attention Deficit/Hyperactivity Disorder, though the effects of modafinil have not been evaluated on working memory in methamphetamine-dependent subjects. This double-blind, placebo-controlled study evaluated whether a daily dose of 400 mg of modafinil, administered over three consecutive days, would enhance performance on a measure of working memory relative to test performance at baseline and following 3 days of placebo administration in 11 methamphetamine addicted, nontreatment-seeking volunteers. The results revealed that participants demonstrating relatively poor performance on the third day of a 3-day washout period (ie, at baseline), showed significant improvement on measures of working memory, but not on measures of episodic memory or information processing speed. In contrast, for participants demonstrating relatively high performance at baseline, modafinil administration did not affect test scores. The findings provide an initial indication that modafinil can reverse methamphetamine-associated impairments in working memory.

The angiotensin-converting enzyme inhibitor perindopril treatment alters cardiovascular and subjective effects of methamphetamine in humans

A variety of medications have been assessed for their potential efficacy for the treatment of methamphetamine dependence. We conducted this study in an attempt to evaluate the potential of a novel class of medications, angiotensin-converting enzyme inhibitors, as treatments for methamphetamine dependence. All participants met the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, third revision (DSM-IV-TR) criteria for methamphetamine abuse or dependence and were not seeking treatment at the time of study entry. The study was conducted using a double-blind design. Subjects received a baseline series of intravenous (IV) doses of methamphetamine (15 mg and 30 mg) and placebo. Subjects received a second identical series of methamphetamine doses 3 and 5 days after initiation of once-daily oral placebo or perindopril treatment. The dose of perindopril was 2 mg, 4mg, or 8 mg administered in the morning. Perindopril treatment was tolerated well. There were no main effects of perindopril on methamphetamine-induced changes in cardiovascular or subjective effects. There were significant perindoprilmethamphetamine interactions for diastolic blood pressure and for ratings of "Any Drug Effect", indicating inverted U dose-effect functions for these indices.

Methamphetamine craving induced in an online virtual reality environment

The main aim of this study was to assess self-reported craving and physiological reactivity in a methamphetamine virtual reality (METH-VR) cue model created using Second Life, a freely available online gaming platform. Seventeen, non-treatment seeking, individuals that abuse methamphetamine (METH) completed this 1-day, outpatient, within-subjects study. Participants completed four test sessions: 1) METH-VR, 2) neutral-VR, 3) METH-video, and 4) neutral-video in a counterbalanced (Latin square) fashion. The participants provided subjective ratings of urges to use METH, mood, and physical state throughout each cue presentation. Measures of physiological reactivity (heart rate variability) were also collected during each cue presentation and at rest. The METH-VR condition elicited the greatest change in subjective reports of "crave METH", "desire METH", and "want METH" at all time points. The "high craving" participants displayed more high frequency cardiovascular activity while the "low craving" participants displayed more low frequency cardiovascular activity during the cue conditions, with the greatest difference seen during the METH-VR and METH-video cues. These findings reveal a physiological divergence between high and low craving METH abusers using heart rate variability, and demonstrate the usefulness of VR cues for eliciting subjective craving in METH abusers, as well as the effectiveness of a novel VR drug cue model created within an online virtual world.

Donepezil treatment and the subjective effects of intravenous cocaine in dependent individuals

Acetylcholinesterase (AChE) inhibitors increase synaptic levels of acetylcholine (ACh) by inhibiting its breakdown. Donepezil is a reversible AChE inhibitor that is clinically available and relatively selective for inhibiting AChE but not other cholinesterases. Because AChE inhibitors have been shown to decrease the reinforcing effects of cocaine in animals, our hypothesis was that pretreatment with donepezil would attenuate the perceived value and other positive subjective effects of cocaine. We conducted a within-subject, double-blind, placebo-controlled, laboratory-based evaluation of the subjective effects produced by intravenous cocaine in human subjects receiving oral donepezil. Following three days of daily treatment with 5mg of donepezil or oral placebo, participants received intravenous placebo or cocaine (0.18 and 0.36 mg/kg). After a three-day washout period, participants were crossed over to the opposite oral treatment, which was followed by identical intravenous infusions. Donepezil was well-tolerated with only two drug-related adverse events reported that were mild and self-limiting. Treatment with donepezil increased ratings of 'any' and 'good' drug effect produced by low-dose cocaine, without modifying the response to high-dose cocaine. When collapsed across intravenous dose, treatment with donepezil decreased dysphoric effects and somatic symptoms, but did not modify the value of cocaine injections as determined by the Multiple Choice Questionnaire (MCQ). In summary, pretreatment with donepezil potentiated some measures for nonspecific and positive effects of low-dose cocaine. Across all intravenous treatments, participants receiving donepezil reported fewer somatic-dysphoric effects. Neither of these actions support the value of donepezil as a treatment for cocaine dependence.

Influence of verbal recall of a recent stress experience on anxiety and desire for cocaine in non-treatment seeking, cocaine-addicted volunteers

It has long been postulated that stress increases the risk of drug abuse and relapse. The principal goal of this project was to evaluate the effects of verbal recall of a recent stress experience (specifically meaningful to each individual) on physiological and subjective measures in cocaine-addicted participants. Subjects described a recent stressful non-drug-related experience and a neutral non-stressful experience, and then completed mood and drug effect questionnaires, while heart rate and blood pressure were recorded. Participants (N = 25) were predominantly African American and male. As a group, participants used cocaine for more than 15 years and approximately 18 of the last 30 days, and a majority reported use of nicotine and/or alcohol. All participants were evaluated during a time in which they tested positive for cocaine metabolite. On a scale of 1-10, participants reported their verbal recall of a recent stress event as highly stressful and their verbal recall of a recent neutral event as non-stressful (p < 0.0001). The self-reported vividness of this recall was high (>8 out of 10) for both the stress and neutral events. Heart rate and systolic and diastolic blood pressure did not differ after verbal recall of either stress or neutral events. Similarly, self-reported subjective effects (including ratings of anxiety and craving for cocaine) did not differ after verbal recall of either stress or neutral events. In summary, despite the fact that participants recounted highly stressful and vivid memories, this experience did not elicit significant changes in cardiovascular or subjective effects. These data suggest that simply recalling a stressful event may not be a sufficient enough stimulus to contribute to craving or relapse in cocaine-addicted individuals.

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.

Methamphetamine Cured my Cocaine Addiction

Cocaine dependence is an enduring problem and years of research and drug development has yet to produce an efficacious pharmacotherapy. Recent clinical research suggests that chronic treatment with amphetamine-like medications produces tolerance to cocaine's reinforcing effects and may offer a viable pharmacotherapy. Three methamphetamine-dependent participants that had been in our clinical laboratory experiments and previously addicted to cocaine are reviewed. Data obtained from initial screen and informal conversation suggested that all participants considered methamphetamine to have helped them stop using cocaine and eliminate cocaine craving. Methamphetamine also significantly decreased their alcohol consumption but did not alter cannabis or nicotine use.

Pilot safety evaluation of varenicline for the treatment of methamphetamine dependence

Despite the worldwide extent of methamphetamine dependence, no medication has been shown to effectively treat afflicted individuals. One relatively unexplored approach is modulation of cholinergic system function. Animal research suggests that enhancement of central cholinergic activity, possibly at nicotinic acetylcholine receptors (nAChRs), can reduce methamphetamine-related behaviors. Further, preliminary findings indicate that rivastigmine, a cholinesterase inhibitor, may reduce craving for methamphetamine after administration of the drug in human subjects. We therefore performed a double-blind, placebo-controlled, crossover pilot study of the safety and tolerability of varenicline in eight methamphetamine-dependent research subjects. Varenicline is used clinically to aid smoking cessation, and acts as a partial agonist at α4b2 nAChRs with full agonist properties at α7 nAChRs. Oral varenicline dose was titrated over one week to reach 1 mg twice daily, and then was co-administered with 30 mg methamphetamine, delivered in 10 intravenous (iv) infusions of 3 mg each. Varenicline was found to be safe in combination with iv methamphetamine, producing no cardiac rhythm disturbances or alterations in vital sign parameters. No adverse neuropsychiatric sequelae were detected either during varenicline titration or following administration of methamphetamine. The results suggest that varenicline warrants further investigation as a potential treatment for methamphetamine dependence.

Theories of addiction: methamphetamine users' explanations for continuing drug use and relapse

A variety of preclinical models have been constructed to emphasize unique aspects of addiction-like behavior. These include Negative Reinforcement ("Pain Avoidance"), Positive Reinforcement ("Pleasure Seeking"), Incentive Salience ("Craving"), Stimulus Response Learning ("Habits"), and Inhibitory Control Dysfunction ("Impulsivity"). We used a survey to better understand why methamphetamine-dependent research volunteers (N = 73) continue to use methamphetamine, or relapse to methamphetamine use after a period of cessation of use. All participants met DSM-IV criteria for methamphetamine abuse or dependence, and did not meet criteria for other current Axis I psychiatric disorders or dependence on other drugs of abuse, other than nicotine. The questionnaire consisted of a series of face-valid questions regarding drug use, which in this case referred to methamphetamine use. Examples of questions include: "Do you use drugs mostly to make bad feelings like boredom, loneliness, or apathy go away?", "Do you use drugs mostly because you want to get high?", "Do you use drugs mostly because of cravings?", "Do you find yourself getting ready to take drugs without thinking about it?", and "Do you impulsively take drugs?". The scale was anchored at 1 (not at all) and 7 (very much). For each question, the numbers of participants rating each question negatively (1 or 2), neither negatively or affirmatively (3-5), and affirmatively (6 or 7) were tabulated. The greatest number of respondents (56%) affirmed that they used drugs due to "pleasure seeking." The next highest categories selected were "impulsivity" (27%) and "habits"(25%). Surprisingly, many participants reported that "pain avoidance" (30%) and "craving" (30%) were not important for their drug use. Results from this study support the contention that methamphetamine users (and probably other drug users as well) are more heterogeneous than is often appreciated, and imply that treatment development might be more successful if treatments targeted subtypes of patients, though a range of limitations to the approach used are acknowledged.

Quantitative EEG abnormalities are associated with memory impairment in recently abstinent methamphetamine-dependent individuals

This study examined the association between brain electrical activity, measured using quantitative electroencephalography (QEEG), and performance on measures of episodic memory in a sample of nine methamphetamine-dependent individuals who were evaluated after 4 days of monitored abstinence and 10 non-drug-using comparison subjects. In methamphetamine users, but not in comparison subjects, increased theta power was correlated with poorer performance on the delayed recall subtests of the Rey Auditory Verbal Learning Test and the Rey-Osterrieth Complex Figure Test (p<0.05). There was no association between alpha, beta, and delta power and performance on the memory tests. These results complement previous findings by demonstrating that the electrophysiological abnormalities associated with methamphetamine dependence are likely to affect behavior in an observable and important manner (i.e., memory deficits) when users are not intoxicated.

Predictors of cardiovascular response to methamphetamine administration in methamphetamine-dependent individuals

The goal of the present investigation was to determine predictors of cardiovascular response to methamphetamine administrated in the laboratory. Heart rate (HR) and blood pressure (BP) were measured at baseline and at several time points following the administration of methamphetamine or saline placebo. One-way ANOVA was used to determine the differences between female and male subjects in their cardiovascular response. In male subjects, linear regression and one-way ANOVA were used to determine the influence of potential predictors on cardiovascular response, including age, weight, drug use indicators, concurrent use of other substances, route of administration, and race. Methamphetamine administration provoked significant increases in HR and BP, as compared to placebo. Female gender was associated with larger peak change in diastolic BP following administration. Baseline HR and BP were found to be strong predictors of cardiovascular response to methamphetamine administration in male subjects. Lifetime use and recent use of methamphetamine and nicotine did not predict cardiovascular response to methamphetamine. Recent alcohol use was associated with increased peak change in diastolic BP. Also, current use of cannabis was negatively correlated with peak HR change. Male cannabis users show lower peak change in HR as compared to non-cannabis users. As compared to methamphetamine smokers, intravenous users demonstrated higher peak change in diastolic BP following drug administration. Race did not have a significant effect on cardiovascular response. Taken together, these findings may help in the prevention and treatment of cardiovascular events in a population at high risk of premature morbidity and mortality.

Presence and persistence of psychotic symptoms in cocaine- versus methamphetamine-dependent participants

The primary objective of this study was to compare and contrast psychotic symptoms reported by cocaine- and methamphetamine-dependent individuals. Participants included 27 cocaine-dependent and 25 methamphetamine-dependent males, as well as 15 cocaine-dependent and 18 methamphetamine-dependent females. After screening, participants were excluded if they met criteria for any Axis I diagnosis other than nicotine dependence, or methamphetamine or cocaine dependence (ie, participants had to use either methamphetamine or cocaine but were excluded if they met dependence criteria for both). The participants were administered the newly developed Psychotic Symptom Assessment Scale (PSAS), which assesses psychotic symptoms. A high proportion of both cocaine- and methamphetamine-dependent men and women reported delusions of paranoia and auditory hallucinations. However, during the abstinent and intoxicated conditions, methamphetamine-dependent men and women were more likely than cocaine-dependent men and women to report psychotic symptoms. Future studies will compare psychotic symptoms reported by non-dependent recreational stimulant users to stimulant-dependent individuals.

The acetylcholinesterase inhibitor rivastigmine does not alter total choices for methamphetamine, but may reduce positive subjective effects, in a laboratory model of intravenous self-administration in human volunteers

A human laboratory model of intravenous methamphetamine self-administration may facilitate study of putative treatments for methamphetamine addiction. We conducted a double-blind, placebo-controlled, between groups investigation of the acetylcholinesterase (AChE) inhibitor rivastigmine in non-treatment-seeking volunteers who met criteria for methamphetamine abuse or dependence. Safety and subjective effects data derived from days 1-10 of this protocol are described in a separate publication. In this report, we describe self-administration outcomes in participants randomized to treatment with rivastigmine (0 mg, N=7; 1.5 mg, N=6; 3 mg, N=9); data that were collected on days 11-15 of the inpatient protocol. On day 11, participants sampled two infusions of methamphetamine (0 and 30 mg, i.v.). On days 12-15, participants made ten choices each day to receive an infusion of either methamphetamine (3 mg, IV) or saline or a monetary alternative ($0.05-$16). The study design allowed for evaluation of differences in behavior on days in which infusions were performed by the physician (experimenter-administered) versus by the participant using a PCA pump (self-administered), and when monetary alternatives were presented in either ascending or descending sequence. The data show that rivastigmine (1.5 and 3 mg), as compared to placebo, did not significantly alter total choices for methamphetamine (p=0.150). Importantly, the number of infusion choices was greater when methamphetamine was available then when saline was available (p<0.0001), and the number of money choices was greater when saline was available then when methamphetamine was available (p<0.0001). The total number of choices for methamphetamine was not altered as a function of a participant's preferred route of methamphetamine use (p=0.57), and did not differ significantly whether they were experimenter-administered or self-administered (p=0.30). In addition, total choices for methamphetamine were similar made when money was available in an ascending versus descending sequence (p=0.49). The participants' years of methamphetamine use, recent use of methamphetamine (in the past 30 days), or baseline craving (indexed here as "Desire") on the day of the self-administration task were not predictive of number of choices for methamphetamine. In a subset of participants (N=8) for which data was available, individual dose of methamphetamine (3 x 3 mg, i.v.) produced significant increases in positive subjective effects, and a preliminary analysis revealed that 3 mg rivastigmine was associated with reductions in these responses, as compared to placebo. In summary, the current report indicates that there were no effects of rivastigmine on total choices for methamphetamine, that there were low levels of methamphetamine self-administration but these were 8 times greater than saline, and that choice behavior was insensitive to alternative reinforcers. In addition, we showed that rivastigmine may reduce the positive subjective effects produced by methamphetamine during self-administration.

Pathological gamblers demonstrate frontal lobe impairment consistent with that of methamphetamine-dependent individuals

Using tests that are frequently administered by neuropsychologists, the authors investigated whether pathological gambling is associated with frontal lobe abnormalities. The sample comprised 10 pathological gamblers, 25 methamphetamine-dependent subjects, and 19 matched comparison subjects. The pathological gamblers and methamphetamine-dependent subjects performed significantly less well than comparison subjects, and the gamblers' test scores were comparable to those of the methamphetamine-dependent participants. The overall magnitude of the effect size was large. These findings demonstrate that the severity of frontal lobe dysfunction in pathological gambling is similar to that observed in methamphetamine-dependent individuals on frequently used clinical measures.