Search PubMed⌕ Search

Biomedical subjects

Walter Ling

Publications and source records attributed to Walter Ling.

At least 19 recordsLinked to original sources
PubMed2006

Randomized, placebo-controlled trial of baclofen and gabapentin for the treatment of methamphetamine dependence.

OBJECTIVE: To conduct a 16-week, randomized, placebo-controlled, double-blind trial of two GABAergic medications, baclofen (20 mg tid) and gabapentin (800 mg tid), for the treatment of methamphetamine dependence. METHODS: Adults with methamphetamine dependence were randomized to one of three conditions for 16 weeks: baclofen (n = 25), gabapentin (n = 26) or placebo (n = 37). All participants attended clinic thrice weekly to receive study medication and psychosocial counseling, complete study assessments, and provide urine samples. RESULTS: No statistically significant main effects for baclofen or gabapentin in reducing methamphetamine use were observed using a generalized estimating equation (GEE). A significant treatment effect was found in post hoc analyses for baclofen, but not gabapentin, relative to placebo among participants who reported taking a higher percentage of study medication (significant treatment group and medication adherence interaction in GEE model of methamphetamine use). CONCLUSIONS: While gabapentin does not appear to be effective in treating methamphetamine dependence, baclofen may have a small treatment effect relative to placebo. Future studies evaluating the effectiveness of baclofen and other GABAergic agents for treatment of methamphetamine may be warranted.

Adult↗
PubMed2006

Randomized, placebo-controlled trial of sertraline and contingency management for the treatment of methamphetamine dependence.

BACKGROUND: Methamphetamine dependence and associated medical and psychiatric concerns are significant public health issues. This project evaluated the efficacy of sertraline (50mg bid) and contingency management (CM) for the treatment of methamphetamine dependence. METHOD: In this randomized, placebo-controlled, double-blind trial, participants completed a 2-week non-medication baseline and were randomized to one of four conditions for 12 weeks: sertraline plus CM (n=61), sertraline-only (n=59), matching placebo plus CM (n=54), or matching placebo-only (n=55). All participants attended clinic thrice-weekly for data collection, medication dispensing, and relapse prevention groups. Outcomes included methamphetamine use (urine drug screening and self-reported days of use), retention (length of stay), drug craving (visual analogue scale), and mood symptoms (Beck Depression Inventory). RESULTS: No statistically significant main or interaction effects for sertraline or CM in reducing methamphetamine use were observed using a generalized estimating equation (GEE), although post hoc analyses showed the sertraline-only condition had significantly poorer retention than other conditions (chi(2) (3)=8.40, p<0.05). Sertraline conditions produced significantly more adverse events than placebo conditions. A significantly higher proportion of participants in CM conditions achieved three consecutive weeks of methamphetamine abstinence than those in non-CM conditions. CONCLUSIONS: These data do not demonstrate improved outcomes for sertraline versus placebo for treatment of methamphetamine dependence; indeed, they suggest sertraline is contraindicated for methamphetamine dependence. Findings provide support for the use of contingency management for treatment of methamphetamine dependence.

Adult↗
PubMed2006

Methadone maintenance patients are cross-tolerant to the antinociceptive effects of very high plasma morphine concentrations.

Opioid dependent patients require higher than normal doses of opioid analgesics. However, this regimen has not been formally tested. This study utilised a double-blind placebo-controlled design to examine antinociceptive responses to saline and pseudo-steady-state plasma morphine concentrations (173+/-11 (mean+/-SEM), range 106-305 ng/ml) in 18 methadone participants in three stable, once daily methadone dose ranges 11-45 mg (n=6), 46-80 mg (n=6), 81-115 mg (n=6) and 10 controls. Testing commenced approximately 20 h after the maintenance dose with the next dose given 1h after morphine cessation. Nociceptive stimuli (cold pressor (seconds) and electrical stimulation (volts)) were used to measure pain detection threshold and pain tolerance. Blood samples were analysed by HPLC for plasma morphine and R-(-)-methadone concentrations. Methadone participants were hyperalgesic to cold pressor pain. High plasma morphine concentrations failed to significantly change cold pressor and electrical stimulation pain tolerance for methadone patients, but in controls, morphine significantly (P<0.05) increased mean pain tolerance to cold pressor by 59+/-29% (range -17% to 311%) and electrical stimulation by 19+/-6% (range 0% to 58%). Morphine significantly (P<0.05) decreased respiration rates by 12+/-3% (range -29% to 8%) in methadone subjects. On saline days, rising methadone concentrations significantly (P<0.01) increased cold pressor pain detection threshold by 32+/-6% (range 1-81%) and cold pressor pain tolerance by 23+/-6% (range -32% to 56%). Methadone maintained patients are hyperalgesic and cross-tolerant to the antinociceptive effects of very high plasma morphine concentrations. While even higher morphine doses may achieve some pain relief, this may be at the cost of unacceptable respiratory depression.

Adult↗
PubMed2006

Management of methamphetamine abuse and dependence.

Preliminary implications for evidence-based treatments and future practice may be drawn from new research findings that inspire a fresh view of methamphetamine dependence and associated medical consequences. Current user populations include increasingly impacted subgroups (ie, youths, women, men who have sex with men, and rural residents); complex consequences of methamphetamine abuse among these subgroups require additional efforts involving contextual understanding of characteristics and needs to develop effective treatments. The neurobiological data on cellular activity of methamphetamine taken with findings from neuroimaging studies indicate potential targets for pharmacologic interventions. In early trials, several candidate medications--bupropion, modafinil, and, to a lesser extent, baclofen--have shown promise in treating aspects of methamphetamine dependence, including aiding memory function necessary to more effectively participate in and benefit from behavioral therapies. Clinicians and researchers must interact to efficiently address the problems of methamphetamine dependence, a major drug problem in the United States and the world.

Baclofen↗
PubMed2006

A comparison of contingency management and cognitive-behavioral approaches for stimulant-dependent individuals.

AIMS: Previous research has reported that both contingency management (CM) and cognitive-behavioral therapy (CBT) are efficacious interventions for the treatment of stimulant abusers. The present study sought to directly compare the effectiveness of (CM) and (CBT) alone and in combination in reducing stimulant use. DESIGN: Randomized clinical trial. PARTICIPANTS: Stimulant-dependent individuals (n = 171). INTERVENTION: CM, CBT or combined CM and CBT, 16-week treatment conditions. CM condition participants received vouchers for stimulant-free urine samples. CBT condition participants attended three 90-minute group sessions each week. MEASUREMENTS: Participants were interviewed at baseline and weeks 17, 26 and 52. Measures included psychiatric disorders and alcohol and drug use and concomitant social problems. FINDINGS: CM procedures produced better retention and lower rates of stimulant use during the study period. Self-reported stimulant use was reduced from baseline levels at all follow-up points for all groups and urinalysis data did not differ between groups at follow-up. While CM produced robust evidence of efficacy during treatment application, CBT produced comparable longer-term outcomes. There was no evidence of an additive effect when the two treatments were combined. CONCLUSIONS: This study suggests that CM is an efficacious treatment for reducing stimulant use and is superior during treatment to a CBT approach. CM is useful in engaging substance abusers, retaining them in treatment and helping them achieve abstinence from stimulant use. CBT also reduces drug use from baseline levels and produces comparable outcomes on all measures at follow-up.

Adult↗
PubMed2006

Variation in neurophysiological function and evidence of quantitative electroencephalogram discordance: predicting cocaine-dependent treatment attrition.

Cocaine treatment trials suffer from a high rate of attrition. We examined pretreatment neurophysiological factors to identify participants at greatest risk. Twenty-five participants were divided into concordant and discordant groups following electroencephalogram (EEG) measures recorded prior to a double-blind, placebo-controlled treatment trial. Three possible outcomes were examined: successful completion, dropout, and removal. Concordant (high perfusion correlate) participants had an 85% rate of successful completion, while discordant participants had a 15% rate of successful completion. Twenty-five percent of dropouts and 50% of participants removed were discordant (low perfusion correlate), while only 25% of those who completed were discordant. Failure to complete the trial was not explained by depression, craving, benzoylecgonine levels or quantitative electroencephalogram (QEEG) power; thus cordance may help identify attrition risk.

Adult↗
PubMed2005

Pharmacokinetics, bioavailability and opioid effects of liquid versus tablet buprenorphine.

AIMS: Two tablet formulations of buprenorphine (a buprenorphine mono-product, Subutex, and a buprenorphine/naloxone combination product, Suboxone) are available for use in the treatment of opioid addiction; however, the bulk of the clinical studies supporting its approval by the US Food and Drug Administration (FDA) were conducted with a sublingual liquid preparation. To assist the clinician in interpreting the relevant literature in establishing dosing parameters for prescription of tablet buprenorphine, this study was designed to compare the steady state: (1) pharmacokinetics and bioavailability, and (2) physiological, subjective and objective opiate effects of two 8 mg buprenorphine tablets (16 mg) to those of 1 ml (8 mg/ml) buprenorphine solution based upon early reports suggesting that the bioavailability of the tablet was approximately 50% of that of the liquid. DESIGN: Randomized, open-label, two-way crossover study. SETTING: Inpatient hospitalization for 21 days. PARTICIPANTS: Twenty-four male and females in general good health and meeting DSM-IV criteria for opiate dependence. INTERVENTION: Subjects received one of the two buprenorphine formulations in the first 10-day period, and the other for the second 10-day period with no washout. MEASUREMENTS: Pharmacokinetic analyses, opiate effects and adverse events. FINDINGS: Drug steady state was reached by Day 7 of each 10-day period, area under the curve for 16 mg (two 8 mg) tablets was higher than the solution. The only non-kinetic statistically significant difference observed between the formulations was in changes in total opioid agonist score. CONCLUSIONS: The serum concentration achieved by 16 mg of tablet buprenorphine is higher than that of the 8 mg solution, although differences between physiologic, subjective and objective opioid effects were not noted. The relative bioavailability of tablet versus solution is estimated to be 0.71; thus, with respect to dosing parameters for the tablet, clinicians should consider using less than 16 mg to achieve bioequivalence to the 8 mg solution.

Adult↗
PubMed2005

Cerebral metabolic dysfunction and impaired vigilance in recently abstinent methamphetamine abusers.

BACKGROUND: Methamphetamine (MA) abusers have cognitive deficits, abnormal metabolic activity and structural deficits in limbic and paralimbic cortices, and reduced hippocampal volume. The links between cognitive impairment and these cerebral abnormalities are not established. METHODS: We assessed cerebral glucose metabolism with [F-18]fluorodeoxyglucose positron emission tomography in 17 abstinent (4 to 7 days) methamphetamine users and 16 control subjects performing an auditory vigilance task and obtained structural magnetic resonance brain scans. Regional brain radioactivity served as a marker for relative glucose metabolism. Error rates on the task were related to regional radioactivity and hippocampal morphology. RESULTS: Methamphetamine users had higher error rates than control subjects on the vigilance task. The groups showed different relationships between error rates and relative activity in the anterior and middle cingulate gyrus and the insula. Whereas the MA user group showed negative correlations involving these regions, the control group showed positive correlations involving the cingulate cortex. Across groups, hippocampal metabolic and structural measures were negatively correlated with error rates. CONCLUSIONS: Dysfunction in the cingulate and insular cortices of recently abstinent MA abusers contribute to impaired vigilance and other cognitive functions requiring sustained attention. Hippocampal integrity predicts task performance in methamphetamine users as well as control subjects.

Adult↗
PubMed2005

Apathy predicts hedonic but not craving response to cocaine.

Cocaine-induced craving has been implicated in the maintenance of ongoing cocaine use and is presumed to be mediated by enhanced synaptic availability of monoamines, including dopamine. Apathy is a neuropsychiatric syndrome that is associated with hypodopaminergic functioning and is neurobiologically distinct from depression. Apathy has been observed to be prevalent during the initial phases of abstinence in cocaine-dependent individuals. In the current report, we sought to investigate the relationship between apathy, depression, and craving in response to an acute intravenous administration of cocaine. To this end, sixteen non-treatment seeking volunteers were evaluated. Following acute administration of cocaine (40 mg, IV), patients with low apathy scores exhibited increased craving, whereas patients with high apathy scores exhibited decreased craving. In addition, patients with high apathy scores exhibited increased ratings of the subjective measure of "High", suggesting that high apathy predicts a greater hedonic response in dependence. Self-reported ratings of depression did not account for the observed differences. The data reveal that cocaine-induced craving is not ubiquitous, and may not play a critical role in the maintenance of cocaine dependence. Overall, the findings suggest that apathy predicts hedonic but not craving response to cocaine.

Cocaine↗
PubMed2005

Medications development: successes and challenges.

The National Institute on Drug Abuse has funded a medications program that has concentrated on the development of medications for opiate and cocaine dependence. Levomethadyl acetate (LAAM) and buprenorphine and buprenorphine/naloxone sublingual tablets were developed in conjunction with pharmaceutical partners and approved by the Food and Drug Administration. The remaining challenges for medications development for opiate dependence involves Phase IV studies in special populations, for example, pregnant opiate-dependent patients, and to translate neuroscience-based findings into treatments. Several marketed medications have shown initial efficacy to reduce cocaine use in well-controlled clinical trials. Disulfiram has been shown to reduce cocaine use in several clinical trials, while baclofen, modafinil, naltrexone, ondansetron, tiagabine, and topiramate have shown preliminary efficacy in initial clinical studies. Confirmatory studies of many of these medications is underway. More recently, the NIDA medications program has evaluated medications for their ability to reduce methamphetamine use. To date, no medications tested have shown efficacy to reduce methamphetamine use. Both marketed medications and investigational agents will be tested. Finally, NIDA has begun to test medications for efficacy to reduce cannabis use. Initial studies are underway. Both agonist and antagonist approaches will be evaluated. Additionally, medications will be tested in cannabis-dependent patients for the management of insomnia, withdrawal, and concurrent depression.

Animals↗
PubMed2005

Randomized controlled pilot trial of cabergoline, hydergine and levodopa/carbidopa: Los Angeles Cocaine Rapid Efficacy Screening Trial (CREST).

AIM: This study tested three dopaminergic medications against a common unmatched placebo condition: hydergine 1 mg three times daily (n = 15); levodopa/carbidopa 25/100 mg three times daily (n = 15); cabergoline 0.5 mg per week (n = 15); and placebo three times daily (n = 15) as potential pharmacotherapies for cocaine dependence. DESIGN: The four-parallel group, Cocaine Rapid Efficacy Screening Trial (CREST) design featured a 2-week baseline period followed by randomization to an 8-week medication condition that included 1 hour per week of cognitive behavioral drug counseling. A safety evaluation was conducted 4 weeks after termination. MEASURES: Outcomes included cocaine metabolites measured in urine, retention and self-reports for drug use, cocaine craving, clinical improvement, mood and HIV risk behaviors. RESULTS: Participants assigned to receive cabergoline provided more urine samples negative for cocaine metabolites (42.4%) than those assigned to receive placebo (25.0%), a statistically significant difference after controlling for baseline differences in self-reported cocaine use (F = 2.95, df = 3; P = 0.05). Cabergoline-treated participants demonstrated a significant improvement over placebo from baseline to week 8 when measured using the Addiction Severity Index (ASI) employment subscale (overall change = - 0.09, SD = 0.10, t = 2.36, P < 0.05). Safety and adverse event measures showed similar rates and types of complaints by treatment condition. CONCLUSIONS: These results, combined with the apparent safety of cabergoline when used with this population, provide empirical support for conducting a larger study of the medication.

Adult↗
PubMed2005

A multi-center randomized trial of buprenorphine-naloxone versus clonidine for opioid detoxification: findings from the National Institute on Drug Abuse Clinical Trials Network.

AIMS: The clinical effectiveness of buprenorphine-naloxone (bup-nx) and clonidine for opioid detoxification in in-patient and out-patient community treatment programs was investigated in the first studies of the National Institute of Drug Abuse Clinical Trials Network. DESIGN: Diagnostic and Statistical Manual version IV (DSM IV)-diagnosed opioid-dependent individuals seeking short-term treatment were randomly assigned, in a 2 : 1 ratio favoring bup-nx, to a 13-day detoxification using bup-nx or clonidine. METHODS: A total of 113 in-patients (77 bup-nx, 36 clonidine) and 231 out-patients (157 bup-nx, 74 clonidine) participated. Supportive interventions included appropriate ancillary medications and standard counseling procedures guided by a self-help handbook. The criterion for treatment success was defined as the proportion of participants in each condition who were both retained in the study for the entire duration and provided an opioid-free urine sample on the last day of clinic attendance. Secondary outcome measures included use of ancillary medications, number of side effects reported and withdrawal and craving ratings. FINDINGS: A total of 59 of the 77 (77%) in-patients assigned to the bup-nx condition achieved the treatment success criterion compared to eight of the 36 (22%) assigned to clonidine, whereas 46 of the 157 (29%) out-patients assigned to the bup-nx condition achieved the treatment success criterion, compared to four of the 74 (5%) assigned to clonidine. CONCLUSION: The benefits of bup-nx for opioid detoxification are supported and illustrate important ways in which clinical research can be conducted in community treatment programs.

Adult↗
PubMed2004

Structural abnormalities in the brains of human subjects who use methamphetamine.

We visualize, for the first time, the profile of structural deficits in the human brain associated with chronic methamphetamine (MA) abuse. Studies of human subjects who have used MA chronically have revealed deficits in dopaminergic and serotonergic systems and cerebral metabolic abnormalities. Using magnetic resonance imaging (MRI) and new computational brain-mapping techniques, we determined the pattern of structural brain alterations associated with chronic MA abuse in human subjects and related these deficits to cognitive impairment. We used high-resolution MRI and surface-based computational image analyses to map regional abnormalities in the cortex, hippocampus, white matter, and ventricles in 22 human subjects who used MA and 21 age-matched, healthy controls. Cortical maps revealed severe gray-matter deficits in the cingulate, limbic, and paralimbic cortices of MA abusers (averaging 11.3% below control; p < 0.05). On average, MA abusers had 7.8% smaller hippocampal volumes than control subjects (p < 0.01; left, p = 0.01; right, p < 0.05) and significant white-matter hypertrophy (7.0%; p < 0.01). Hippocampal deficits were mapped and correlated with memory performance on a word-recall test (p < 0.05). MRI-based maps suggest that chronic methamphetamine abuse causes a selective pattern of cerebral deterioration that contributes to impaired memory performance. MA may selectively damage the medial temporal lobe and, consistent with metabolic studies, the cingulate-limbic cortex, inducing neuroadaptation, neuropil reduction, or cell death. Prominent white-matter hypertrophy may result from altered myelination and adaptive glial changes, including gliosis secondary to neuronal damage. These brain substrates may help account for the symptoms of MA abuse, providing therapeutic targets for drug-induced brain injury.

Adult↗
PubMed2004

Mood disturbances and regional cerebral metabolic abnormalities in recently abstinent methamphetamine abusers.

BACKGROUND: Mood disturbances in methamphetamine (MA) abusers likely influence drug use, but the neurobiological bases for these problems are poorly understood. OBJECTIVE: To assess regional brain function and its possible relationships with negative affect in newly abstinent MA abusers. DESIGN: Two groups were compared by measures of mood and cerebral glucose metabolism ([18F]fluorodeoxyglucose positron emission tomography) during performance of a vigilance task. SETTING: Participants were recruited from the general community to a research center. PARTICIPANTS: Seventeen abstaining (4-7 days) MA abusers (6 women) were compared with 18 control subjects (8 women). MAIN OUTCOME MEASURES: Self-reports of depressive symptoms and anxiety were measured, as were global and relative glucose metabolism in the orbitofrontal, cingulate, lateral prefrontal, and insular cortices and the amygdala, striatum, and cerebellum. RESULTS: Abusers of MA provided higher self-ratings of depression and anxiety than control subjects and differed significantly in relative regional glucose metabolism: lower in the anterior cingulate and insula and higher in the lateral orbitofrontal area, middle and posterior cingulate, amygdala, ventral striatum, and cerebellum. In MA abusers, self-reports of depressive symptoms covaried positively with relative glucose metabolism in limbic regions (eg, perigenual anterior cingulate gyrus and amygdala) and ratings of state and trait anxiety covaried negatively with relative activity in the anterior cingulate cortex and left insula. Trait anxiety also covaried negatively with relative activity in the orbitofrontal cortex and positively with amygdala activity. CONCLUSIONS: Abusers of MA have abnormalities in brain regions implicated in mood disorders. Relationships between relative glucose metabolism in limbic and paralimbic regions and self-reports of depression and anxiety in MA abusers suggest that these regions are involved in affective dysregulation and may be an important target of intervention for MA dependence.

Adult↗
PubMed2004

The effect of relapse on cognition in abstinent methamphetamine abusers.

Data from 75 participants in a longitudinal study of methamphetamine (MA) abuse were used to differentiate the cognitive performance of those who remained abstinent, relapsed, or continued to use during treatment. Participants were divided into three groups: continuous abstinence, initial abstinence but relapse, and continuous use. Groups did not differ on age, education, gender or ethnicity. Participants in the longitudinal study completed a battery of cognitive tests within 7 days of their last use of MA, then were re-tested monthly for up to 6 months (average time for this analysis was 92 days). For episodic memory, the relapse groups performance was worse than the abstinent and significantly worse than that of the continued use group who had the best performance on all measures. Relapse to methamphetamine use may affect episodic memory differently than it affects the other cognitive functions measured.

Adult↗
PubMed2004

Association between quantitative EEG and neurocognition in methamphetamine-dependent volunteers.

OBJECTIVE: Exposure to methamphetamine is associated with long-lasting reductions in markers for dopaminergic neurons in preclinical models and in humans. These changes may be associated with alterations in brain electrical activity and in cognition. METHODS: The sample included 9 methamphetamine-dependent subjects and 10 non-drug-using volunteers. Methamphetamine-dependent subjects were hospitalized for 4 days to document abstinence; non-drug-using volunteers were studied as outpatients. EEGs were recorded in the eyes-closed resting state, and absolute EEG power in each frequency band (0.5-4 Hz, 4-8 Hz, 8-12 Hz, and 12-20 Hz) was measured using a fast Fourier transform. EEG power was log-transformed prior to analysis. Cognition was measured using computerized reaction time tasks. RESULTS: Within the methamphetamine-dependent group only, increased theta quantitative EEG (QEEG) power correlated significantly with reaction time on tasks that were more difficult or that were degraded by fatigue. Increased theta QEEG power also correlated with reduced accuracy on a working memory task. CONCLUSIONS: Increased QEEG power in the theta band is associated with worse performance on reaction time tasks in the methamphetamine-dependent sample but not in the non-drug-using volunteers. SIGNIFICANCE: Methamphetamine dependence is associated with pathological alterations in brain electrical activity and in cognitive performance. QEEG appears to provide a sensitive measure of methamphetamine-associated alterations in brain function.

Adult↗