Gabapentin abuse in a cocaine user: implications for treatment?

Management of gabapentin misuse in a patient with previous history of opioid use disorder: Case report

We present a 37-year-old male who misuses 12 g of gabapentin per day associated with dependence and withdrawal. He had a previous history of opioid use disorder (OUD) which has been in remission. An outpatient gradual dose reduction regimen was tried and failed and the patient decided to discontinue gabapentin abruptly. Symptomatic medication to relieve gabapentin withdrawal was also unsuccessful and resulted in the reinstatement of OUD. Finally, the patient was stabilized using buprenorphine maintenance treatment and discontinued opioids and gabapentin misuse. The clinical implications and significance of taking regulatory actions to control gabapentin misuse have been discussed.

Current Evidence on Abuse and Misuse of Gabapentinoids

This review summarizes current evidence on the abuse and misuse of the gabapentinoids pregabalin and gabapentin. Pharmacovigilance studies, register-based studies, surveys, clinical toxicology studies, and forensic toxicology studies were identified and scrutinized with the goal to define the problem, identify risk factors, and discuss possible methods to reduce the potential for abuse and misuse. Studies found that gabapentinoids are abused and misused and that individuals with a history of psychiatric disorders or substance use disorder seem to be at high risk. Moreover, some evidence supports the notion that patients with opioid use disorders may be at an increased risk of abusing gabapentinoids. Available evidence also suggests that abuse and misuse are more frequent in users of pregabalin compared with users of gabapentin. Health professionals and prescribers should be aware of the risk for misuse of pregabalin and gabapentin, which eventually could lead to abuse, substance dependence, and intoxications. Prescribing to patients belonging to risk populations such as those with psychiatric disorders or substance use disorder should be avoided if possible and, if prescribed, signs of misuse and abuse should be monitored.

Sociodemographic and clinical correlates of gabapentin receipt with and without opioids among a national cohort of patients with HIV

Gabapentin is commonly prescribed for chronic pain, including to patients with HIV (PWH). There is growing concern regarding gabapentin's potential for harm, particularly in combination with opioids. Among PWH, we examined factors associated with higher doses of gabapentin receipt and determined if receipt varied by opioid use. We examined data from the Veterans Aging Cohort Study, a national prospective cohort including PWH, from 2002 through 2017. Covariates included prescribed opioid dose, self-reported past year opioid use, and other sociodemographic and clinical variables. We used multinomial logistic regression to determine independent predictors of gabapentin receipt. Among 3,702 PWH, 902 (24%) received any gabapentin during the study period at a mean daily dose of 1,469 mg. In the multinomial model, high-dose gabapentin receipt was associated with high-dose benzodiazepine receipt (adjusted odds ratio [aOR], 95% confidence interval [CI]= 1.53, [1.03-2.27]), pain interference (1.65 [1.39-1.95]), and hand or foot pain (1.81, [1.45-2.26]). High-dose gabapentin receipt was associated with prescribed high-dose opioids receipt (2.66 [1.95-3.62]) but not self-reported opioid use (1.03 [0.89-1.21]). PWH prescribed gabapentin at higher doses are more likely to receive high-dose opioids and high-dose benzodiazepines, raising safety concerns.

Patterns of Neonatal Co-Exposure to Gabapentin and Commonly Abused Drugs Observed in Umbilical Cord Tissue

Gabapentin was thought to have low abuse potential, but it is increasingly being abused by people with substance use disorder in an attempt to potentiate the euphoric effects from opioids and other CNS depressants. Additionally, infants co-exposed to gabapentin and opioids during pregnancy tend to exhibit prolonged and more severe neonatal abstinence syndrome. In this study, we describe positivity rates among commonly abused drugs and rates of co-medication with gabapentin in a large dataset of umbilical cord tissue specimens (n = 25,422) submitted for routine newborn drug testing at a national clinical reference laboratory (ARUP Laboratories, Salt Lake City, UT, USA). Detection of prenatal drug exposure in umbilical cord tissue specimens was accomplished using a semi-quantitative liquid chromatography-tandem mass spectrometry assay designed to detect 47 specific drugs and drug metabolites including opioids, stimulants, sedative-hypnotics and hallucinogens. A positive result for at least one of the measured drugs or drug metabolites was reported in 7,054 (28%) of the umbilical cord tissues analyzed. Gabapentin had a positivity rate of ~2% with 562 positive results. Of the 562 gabapentin-positive samples, 395 (70%) also had a positive result for at least one other drug or drug metabolite, with the highest co-positivity rate observed for norbuprenorphine (32%, n = 182) followed by amphetamine (15%, n = 84), buprenorphine (13%, n = 74), methamphetamine (12%, n = 68), morphine (11%, n = 64), fentanyl (10%, n = 54) and naloxone (10%, n = 54). Notably, the concentration of gabapentin in gabapentin-positive umbilical cord specimens was higher in buprenorphine-containing specimens as compared to specimens containing other opioids, stimulants or benzodiazepines. Identification of neonatal co-exposure to gabapentin and opioids, particularly buprenorphine, may guide clinicians in rapid initiation of monitoring and intervention for neonatal abstinence syndrome.

Gabapentin controlled substance status

Gabapentin is approved to treat postherpetic neuralgia and epilepsy with partial-onset seizures. The large majority of gabapentin prescribing is off label. Gabapentin may be abused for euphoria, potentiating the high from opiates, reduction of alcohol cravings, a cocaine-like high, as well as sedation or sleep. Individuals at the highest risk for abusing gabapentin include those with opioid abuse, mental illness, or previous history of prescription drug abuse. States are now taking action to track gabapentin use through prescription monitoring programs, and some states have reclassified it as a Schedule V controlled substance. This commentary summarizes gabapentin's abuse potential, identifies state-level actions regarding gabapentin monitoring, and discusses possible clinical implications and ways to enhance patient safety when prescribing gabapentin.

Profile of Substance Misuse among Adolescent and Young Adult Gabapentinoid Users: A Register-Based Follow-up Study of Former Adolescent Psychiatric Inpatients

Our study examined characteristics of adolescent and young adult study participants using gabapentinoids (gabapentin, pregabalin), with previous history of adolescent psychiatric inpatient hospitalization. Particular focus was on temporal association of age, at first prescription for gabapentinoids, to age at tobacco smoking initiation, regular alcohol use, diagnosis of substance dependence and prescriptions for benzodiazepines and opioids. Methods: The initial study population contained 508 adolescents (300 females, 208 males) admitted to psychiatric inpatient care in Oulu University hospital between the ages 13-17 years. Register-based follow-up information on prescriptions for gabapentinoids, benzodiazepines and opioids, as well as ICD-10 diagnosis for hospital-treated substance dependence, was obtained from the Finnish national health care registers. Results: The users of gabapentinoids accounted for 9.1% of the initial study population. Of adolescence-related characteristics, suicidal ideation, suicide attempts and non-suicidal self-injury was emphasized in females using gabapentinoids. The majority of participants using gabapentinoids had benzodiazepines (80.4%) and opioids (71.7%) as comorbid drugs. Initiation of tobacco smoking and alcohol use and first prescriptions for of benzodiazepines and opioids, and a diagnosis of substance dependence commonly predated first prescriptions for gabapentinoids. Conclusions: In clinical practice, the decision to prescribe gabapentinoids to adolescents or young adults must be made with caution, particularly for those with substance use problems and/or without a clinically approved indication.

Trends in Gabapentin Prescribing in a Commercially Insured U.S. Adult Population, 2009-2016

BACKGROUND

Gabapentin is prescribed for a variety of conditions and is often used off label. It is important to understand the prevalence of gabapentin prescribing and the characteristics of individuals who are prescribed gabapentin, given increasing concern regarding its potential for misuse.

OBJECTIVES

To (a) examine state- and region-level prevalence and trends in gabapentin prescribing from 2009 to 2016 and (b) characterize demographic and clinical characteristics of individuals prescribed gabapentin in a nationwide population of commercially insured adults.

METHODS

This retrospective, longitudinal study examined trends in gabapentin prescribing from 2009 to 2016. The study population included individuals aged 18-64 years who were enrolled in a commercial insurance plan at any point from 2009 to 2016. Individuals who were prescribed gabapentin were defined as beneficiaries with at least 1 gabapentin prescription claim in a calendar year (CY). A cross-sectional descriptive analysis was performed to examine differences in demographic and clinical characteristics of individuals prescribed or not prescribed gabapentin in CY 2016.

RESULTS

The prevalence of gabapentin prescribing nearly doubled from 2009 to 2016. During this time, gabapentin prescribing increased in every state (range: 44%-179%). State-specific prevalence rates in 2016 varied from 12.7 to 43.9 per 1,000 beneficiaries. Overall, 2.7% of beneficiaries filled ≥ 1 gabapentin prescription in 2016. Individuals prescribed gabapentin were more likely to fill opioid prescriptions (60.8% vs. 16.5%, P < 0.01); reside in the South (53.7% vs. 47%, P < 0.01); be female (62.5% vs. 52.3%, P < 0.01); and be aged 55-64 years (41.7% vs. 21.2%, P < 0.01) compared with the comparator. Individuals who were prescribed gabapentin also had significantly higher rates of seizure disorders, neuropathic pain, mental health disorders, substance use disorders, and diabetes.

CONCLUSIONS

The prevalence of gabapentin prescribing among a U.S. privately insured population has increased steadily in recent years. Additional research should examine coprescribing of gabapentin in the context of the opioid epidemic.

DISCLOSURES

The project described in this study was supported by the NIH National Center for Advancing Translational Sciences through grant number UL1TR001998. This study was also partially supported by grant number 2017-PM-BX-K026 (Data-Driven Responses to Prescription Drug Misuse in Kentucky) awarded by the Bureau of Justice Assistance. Viewpoints or opinions in this document are those of the authors and do not necessarily represent the official position or policies of the U.S. Department of Justice or the official views of the NIH. The authors do not have any conflicts of interest to report. Portions of this study have been previously presented in poster presentations at the 2019 Academy Health Annual Research Meeting; June 2-4, 2019; Washington, DC, and the 2019 University of Kentucky Substance Use Research Day; March 3, 2019; Lexington, KY.

An Insight into Gabapentin and Pregabalin in Scottish Prisoners

The aim of this study was to evaluate the prevalence and abuse potential of antiepileptic drugs (AEDs) among prison populations in Scotland, UK. Participants consisted of all admitted and released prisoners over a 1 month period who consented to provide samples. Urine samples were collected and analyzed by liquid chromatography coupled with triple quadrupole tandem mass spectrometry using a method validated for the simultaneous quantification of 21 AEDs in urine. A total of 904 samples were collected. The samples were also screened for drugs of abuse by using point-of-care testing kits. A total of 18% of the samples were positive for AEDs. Gabapentin (GBP) was identified in 118 samples (13%) and pregabalin (PRG) in 32 samples (3.5%). Interestingly, 12 samples contained both drugs (1.3%). The concentrations ranged from 0.5 to 1,100 mg/L (median, 15 mg/L) for GBP and from 0.5 to 440 mg/L (median, 7.3 mg/L) for PRG. Four samples were found to have concentrations &gt;400 mg/L, two samples for GBP and two samples for PRG. These concentrations are at least 20 times above the median concentrations. Other AEDs detected were levetiracetam (four samples), vigabatrin (four samples), lamotrigine (three samples), valproic acid (three samples), carbamazepine (two samples) and topiramate (one sample). Illicit or non-prescribed drugs were detected in 81% of urine samples of which 80% were from admitted prisoners and 20% from released prisoners. Benzodiazepines, opiates and cannabis were the most frequently detected drugs. Other drugs found in positive AED samples were methadone (26%), cocaine (18%), buprenorphine (17%), amphetamines (4%), methamphetamines (4%) and barbiturates (4%). This study shows a high prevalence of AEDs within the Scottish prison system, primarily due to GBP and PRG; however, due to the anonymity of the sample collection, it is unknown if these are prescribed or illicit drug ingestions.

An ethnographic decision model of the initiation of gabapentin misuse among prescription and/or illicit opioid (mis)user

AIMS

Gabapentin is used in the treatment of seizures and neuralgia, and it is prescribed off-label to treat substance use disorders and withdrawal symptoms. Recent research documents misuse of gabapentin, especially among prescription opioid misusers. The present study contributes to this literature by examining the initiation of gabapentin misuse.

METHODS

Qualitative interviews were conducted with prescription and/or illicit opioid (mis)users who reported a history of gabapentin misuse (N = 62) and who did not (N = 29). During semi-structured interviews, respondents provided descriptions of the first time they misused gabapentin. An ethnographic decision model was constructed to illustrate the factors that influence the initiation decision.

RESULTS

Multiple individual, social, and environmental factors influence the decision to initiate gabapentin misuse. Respondents described the initiation decision related to: a) wanting to feel a psychoactive high during times of limited access to one's preferred drug because of institutional barriers (e.g., substance abuse treatment; jail; transitional living facility; N = 18); b) the desire to use multiple drugs, including for experimentation or to potentiate another substance (N = 18); and c) the need to self-treat withdrawal symptoms during periods of opioid nonuse or when opioids were unavailable (N = 16). Respondents also initiated gabapentin misuse to self-treat physical pain (N = 10).

CONCLUSIONS

Multiple approaches are needed to mitigate gabapentin misuse, including limiting availability in institutional settings and informal channels as well as addressing the needs of drug users who experience physical pain and withdrawal symptoms. Continued research is needed to examine therapeutic uses of gabapentin and behaviors related to misuse.

Regulating gabapentin as a drug of abuse: A survey study of Kentucky community pharmacists

OBJECTIVES

As the number of gabapentin prescriptions has increased, so have reports of its misuse and diversion. This trend has led some states to closer monitoring of gabapentin dispensing through prescription drug monitoring programs (PDMPs). The objective of this study was to collect and analyze Kentucky community pharmacists' perceptions of gabapentin misuse and diversion, and their support or opposition to regulatory efforts to reclassify the drug as a controlled substance (CS).

METHODS

Responses were collected using an online survey sent by e-mail to all pharmacists practicing in Kentucky in August 2016. The survey collected basic demographic characteristics and pharmacists' experience with gabapentin dispensing. Descriptive statistics were calculated using question response frequencies. Pearson's chi-squared statistics were calculated to examine the distribution of support for gabapentin as a CS in Kentucky across each of the categories of the individual variables. Logistic regression was used to estimate the effects of pharmacist demographic characteristics and experiences with gabapentin on their support of gabapentin reclassification as a CS.

RESULTS

One thousand seven hundred sixty-nine surveys were collected (response rate = 34.2%). Responding community pharmacists (n = 1084) believe that the abuse and diversion of gabapentin are a problem in their communities, with 9 in 10 (89.6%) indicating that they agree or strongly agree. More than three-fourths (87.5%) indicated support for reclassifying gabapentin as a CS. Common reasons for opposition to gabapentin regulatory changes were that they would not reduce or eliminate abuse (45.8%) and that they would be an inconvenience to patients (17.0%). Pharmacists practicing in independent pharmacies and pharmacists in practice greater than 20 years were less likely to indicate support for gabapentin reclassification.

CONCLUSION

Kentucky community pharmacists express considerable concern over the possible misuse and diversion of gabapentin and widely support regulatory changes reclassifying gabapentin as a CS.

Gabapentin-related suicide: Myth or fact?

Background:

The opioid epidemic in America is real and is estimated to be the number one cause of death in adults under 50 years of age. Finding alternative analgesic medications is part of the effort to decrease the prescription of narcotics, with gabapentin being at the top of the list.

Case Description:

In the present case, we discuss the side-effects of gabapentin, used as part of the multimodal treatment approach of painful spinal degenerative disease. The patient stated that he had noticed personality changes after gabapentin was initiated, and that he had become more depressed, frustrated, and aggressive. His uncontrolled pain and acute mood changes led him to attempt suicide by hanging himself. Gabapentin was discontinued and the patient's suicidal ideation completely subsided.

Conclusion:

It is imperative to screen, identify, and appropriately manage patients with underlying psychiatric disorders prior to initiating pain management with gabapentin. Therefore, it is crucial to raise awareness of gabapentin as a potential cause of depression, aggressive behavior, and suicidal ideation.

How addictive are gabapentin and pregabalin? A systematic review

In the last ten years, gabapentin and pregabalin have been becoming dispensed broadly and sold on black markets, thereby, exposing millions to potential side-effects. Meanwhile, several pharmacovigilance-databases have warned for potential abuse liabilities and overdose fatalities in association with both gabapentinoids. To evaluate their addiction risk in more detail, we conducted a systematic review on PubMed/Scopus and included 106 studies. We did not find convincing evidence of a vigorous addictive power of gabapentinoids which is primarily suggested from their limited rewarding properties, marginal notes on relapses, and the very few cases with gabapentinoid-related behavioral dependence symptoms (ICD-10) in patients without a prior abuse history (N=4). In support, there was no publication about people who sought treatment for the use of gabapentinoids. Pregabalin appeared to be somewhat more addictive than gabapentin regarding the magnitude of behavioral dependence symptoms, transitions from prescription to self-administration, and the durability of the self-administrations. The principal population at risk for addiction of gabapentinoids consists of patients with other current or past substance use disorders (SUD), mostly opioid and multi-drug users, who preferred pregabalin. Pure overdoses of gabapentinoids appeared to be relative safe but can become lethal (pregabalin > gabapentin) in mixture with other psychoactive drugs, especially opioids again and sedatives. Based upon these results, we compared the addiction risks of gabapentin and pregabalin with those of traditional psychoactive substances and recommend that in patients with a history of SUD, gabapentinoids should be avoided or if indispensable, administered with caution by using a strict therapeutic and prescription monitoring.

A Decade of Gabapentinoid Misuse: An Analysis of the European Medicines Agency's 'Suspected Adverse Drug Reactions' Database

INTRODUCTION

The gabapentinoids pregabalin and gabapentin are being increasingly prescribed for a range of clinical conditions. Recently, although gabapentinoids at therapeutic dosages may present with low addictive liability levels, cases of misuse and rising numbers of related fatalities have been reported.

OBJECTIVES

The aim of the study was to identify and assess cases of gabapentinoid misuse or dependence as reported to the European Medicines Agency's EudraVigilance database, to identify the magnitude of this problem and the characteristics of these reactions.

METHODS

All spontaneous reports of both gabapentin- (2004-2015) and pregabalin- (2006-2015) related misuse/abuse/dependence were retrieved. A descriptive analysis by source, sex, age, and type of report was performed.

RESULTS

From the EudraVigilance database 7639 (6.6 % of a total of 115,616) and 4301 (4.8 % of 90,166) adverse drug reaction reports of misuse/abuse/dependence were, respectively, associated with pregabalin and gabapentin, with an overall reporting frequency increasing over time. For both molecules, subjects typically involved were female adults. A total of 27 and 86 fatalities, respectively, associated with pregabalin and gabapentin, and mostly in combination with opioids, were identified. Analysis of proportional reporting ratios for drug abuse/dependence/intentional product misuse values seem to indicate that these adverse drug reactions were more frequently reported for pregabalin (1.25, 1.39, and 1.58, respectively) compared with gabapentin.

CONCLUSIONS

Despite data collection/methodological approach limitations, the present data seem to suggest that gabapentinoid misuse may be a cause for concern, especially in patients with a history of substance misuse. Hence, healthcare professionals should be vigilant when prescribing these molecules.

Gabapentin misuse, abuse and diversion: a systematic review

BACKGROUND AND AIMS

Since its market release, gabapentin has been presumed to have no abuse potential and subsequently has been prescribed widely off-label, despite increasing reports of gabapentin misuse. This review estimates and describes the prevalence and effects of, motivations behind and risk factors for gabapentin misuse, abuse and diversion.

METHODS

Databases were searched for peer-reviewed papers demonstrating gabapentin misuse, characterized by taking a larger dosage than prescribed or taking gabapentin without a prescription, and diversion. All types of studies were considered; grey literature was excluded. Thirty-three papers met inclusion criteria, consisting of 23 case studies and 11 epidemiological reports. Published reports came from the United States, the United Kingdom, Germany, Finland, India, South Africa and France, and two analyzed websites not specific to a particular country.

RESULTS

Prevalence of gabapentin misuse in the general population was reported to be 1%, 40-65% among individuals with prescriptions and between 15 and 22% within populations of people who abuse opioids. An array of subjective experiences reminiscent of opioids, benzodiazepines and psychedelics were reported over a range of doses, including those within clinical recommendations. Gabapentin was misused primarily for recreational purposes, self-medication or intentional self-harm and was misused alone or in combination with other substances, especially opioids, benzodiazepines and/or alcohol. Individuals with histories of drug abuse were most often involved in its misuse.

CONCLUSIONS

Epidemiological and case report evidence suggests that the anti-epileptic and analgesic medication gabapentin is being misused internationally, with substance abuse populations at special risk for misuse/abuse.

Gabapentin: Abuse, Dependence, and Withdrawal

OBJECTIVE

To identify case reports and studies regarding patients who abused, became dependent on, or experienced withdrawal from gabapentin.

DATA SOURCES

A PubMed literature search (1993 to October 2015) was performed using the search terms gabapentin, withdrawal, dependence, and addiction. Additional references were identified from a review of literature citations.

STUDY SELECTION

All English-language case reports and studies were evaluated.

DATA SYNTHESIS

A total of 18 case reports or case series were identified regarding addiction to or withdrawal from gabapentin. All the cases of addiction were in patients who had a previous history of alcohol, cocaine, or opioid abuse. On average, the patients were taking more than 3000 mg/d (600-8000 mg/d). Two surveys reported that the misuse of gabapentin was 1.1% in the general population and 22% in drug abuse treatment centers. Withdrawal, when reported, occurred within 12 hours to 7 days of discontinuation of the medication.

CONCLUSION

There have been numerous documented cases of gabapentin abuse, dependence, and withdrawal. Even though gabapentin is sometimes considered as a treatment option for alcohol and substance abuse, it is important to monitor for drug-seeking behaviors. A history of alcohol or substance abuse appears to be an important part of a patient's medical history when evaluating their risk for addiction and dependence behaviors. Health care providers need to be aware of this risk in their patients and monitor their patients for signs of abuse and dependence along with withdrawal symptoms.

Gabapentinoid abuse in order to potentiate the effect of methadone: a survey among substance misusers

BACKGROUND/AIMS

There is emerging evidence of gabapentin and pregabalin (gabapentinoid) abuse, particularly in the substance misuse population, and some suggestion of gabapentinoids being abused alongside methadone.

METHODS

A questionnaire-based survey was carried out in six substance misuse clinics, looking for evidence of gabapentinoid abuse.

RESULTS

22% (29/129) of respondents admitted to abusing gabapentinoids, and of these, 38% (11/29) abused gabapentinoids in order to potentiate the 'high' they obtained from methadone.

CONCLUSIONS

Gabapentinoid abuse along with methadone has not previously been described. These findings are of relevance to clinicians working within both substance misuse services and chronic pain services.

Pharmacological treatment of insomnia in alcohol recovery: a systematic review

AIMS

To conduct a systematic review of pharmacological agents used to treat sleep problems in alcohol recovery.

METHODS

In accordance with the Quorum statement, we searched PubMed, EMBASE, Psych Info and Medline databases using the terms alcohol, insomnia/sleep and treatment/management with no year/language restrictions.

RESULTS

The search revealed 1239 articles and 20 met inclusion criteria. Trazodone was compared against placebo and found to be superior in two trials. Trazodone and gabapentin improved sleep measures with gabapentin performing significantly better in an open-label study. The data regarding gabapentin are equivocal with few studies showing a clear benefit. In one randomized trial, topiramate resulted in improved subjective sleep measures and a reduction in the percentage of heavy drinking days. Two randomized control trials of carbamazepine revealed improvement in subjective sleep measures. A randomized study showed lormetazepam was better than zopiclone on some measures. In a small placebo-controlled trial, acamprosate was found to result in improvements on some sleep measures. In single, small, mostly open-label studies, quetiapine, triazolam, ritanserin, bright light and magnesium have shown efficacy, while chlormethiazole, scopolamine and melperone showed no difference or worsening.

CONCLUSION

Trazodone has the most data suggesting efficacy. This finding is tempered by a study suggesting its association with a return to heavy drinking in some patients. Data regarding the efficacy of gabapentin are unclear at this point.

Effects of gabapentin on cocaine self-administration, cocaine-triggered relapse and cocaine-enhanced nucleus accumbens dopamine in rats

Gabapentin is a gamma-aminobutyric acid (GABA) analogue, with GABAmimetic pharmacological properties. Gabapentin is used for the treatment of seizures, anxiety and neuropathic pain. It has been proposed that gabapentin may be useful in the treatment of cocaine dependence. However, clinical trials with gabapentin have shown conflicting results, while preclinical studies are sparse. In the present study, we investigated the effects of gabapentin on intravenous cocaine self-administration and cocaine-triggered reinstatement of drug-seeking behavior, as well as on cocaine-enhanced dopamine (DA) in the nucleus accumbens (NAc). We found that gabapentin (25-200 mg/kg, i.p., 30 min or 2 h prior to cocaine) failed to inhibit intravenous cocaine (0.5 mg/kg/infusion) self-administration under a fixed-ratio reinforcement schedule or cocaine-triggered reinstatement of cocaine-seeking behavior. In vivo microdialysis showed that the same doses of gabapentin produced a modest increase (approximately 50%, p<0.05) in extracellular NAc GABA levels, but failed to alter either basal or cocaine-enhanced NAc DA. These data suggest that gabapentin is a weak GABA-mimic drug. At the doses tested, it has no effect in the addiction-related animal behavioral models here tested. This is in striking contrast to positive findings in the same animal models shown by another GABAmimetic--gamma-vinyl GABA (see companion piece to present article).

Antiepileptic drugs for the treatment of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a disruptive, chronic, and relatively common disorder that is often difficult to treat. Many patients with PTSD are unresponsive, have only moderate or marginal responses, or have troubling side effects to first-line serotonin reuptake inhibitor treatment. Studies suggest that antiepileptic drugs (AEDs) may be an effective treatment alternative or adjunctive treatment for the symptoms of PTSD. Recent results from case reports and open and controlled studies on the efficacy and tolerability of AEDs in PTSD are reviewed here, and their methodological limitations are discussed when relevant. AEDs shown to be effective in double-blind, placebo-controlled trials of PTSD include lamotrigine, topiramate, and tiagabine. Other AEDs that appear promising in open-label trials of PTSD include carbamazepine, valproate, gabapentin, vigabatrin, phenytoin, and levetiracetam. Stress-activated limbic kindling may be involved in the pathogenesis of PTSD. The possibility that AEDs may be effective in the treatment of PTSD due to their antikindling effect is discussed, and suggestions for future research are made.

A randomized placebo-controlled trial of gabapentin for cocaine dependence

BACKGROUND

In laboratory animals, augmentation of GABA neurotransmission results in inhibition of cocaine self-administration and inhibition of reinstatement to cocaine-seeking behaviors. If parallel effects were observed in humans, GABA-ergic medication should be effective both in the abstinence-induction as well as in the relapse-prevention phase of cocaine dependence treatment. Gabapentin is an anticonvulsant medication that increases human brain GABA levels. We evaluated the safety and efficacy of gabapentin combined with relapse-prevention therapy in the treatment of cocaine-dependent individuals.

DESIGN

The study involved 129 individuals with cocaine dependence. Of the 99 participants, who were randomized into a double-blind trial 88% were males, 66% were minorities and with an average age of 39 years (range 22-58 years). After 2 weeks of placebo lead-in, participants were randomized to receive either gabapentin 3200 mg (1600 mg bid) or placebo for 12 weeks, followed by 2 weeks of placebo lead-out. Prior to randomization, participants were stratified into four groups based on the principal route of cocaine use (smokers versus intranasal users) and the level of cocaine use during the 2 weeks of lead-in (high level versus low level). Throughout the 16 weeks study, participants received weekly individual relapse-prevention therapy. The outcome measures included: days of cocaine use and a binary indicator of abstinence based on urine toxicology test, self-reported cocaine craving and retention in treatment.

RESULTS

Forty-nine percent of randomized patients completed 12 weeks of the trial. Retention did not differ by treatment group but cocaine-smokers dropped out of treatment at a significantly faster rate than intranasal users. For the entire sample, odds of cocaine use over the course of the study did not differ between gabapentin- and placebo-treated individuals. There was a significant difference in the odds of cocaine use between high and low-use groups, with the odds in high-use groups decreasing over time and odds in the low-use groups gradually increasing over the course of the study, such that by the end of the study low and high users were similarly likely to use cocaine. In the low-use group, there was a non-significant trend suggesting that gabapentin-treated subjects had more favorable outcome compared to placebo-treated individuals. There was no treatment effect on abstinence rates, craving or other substance use. Gabapentin at 3200 mg/day was very well tolerated in this group of cocaine-dependent participants.

CONCLUSIONS

When combined with weekly individual relapse-prevention therapy, gabapentin 1600 mg bid was no more effective than placebo in the treatment of cocaine dependence. When reviewed in conjunction with other published studies, gabapentin and other GABA enhancing anticonvulsant medications may deserve further study as relapse-preventive agents in cocaine-dependent individuals who achieve abstinence early in treatment.

Smoked cocaine discrimination in humans: effects of gabapentin

Gamma-aminobutyric acid (GABA) agonists, such as the GABA analogue, gabapentin, may provide new avenues for pharmacological treatment of cocaine dependence. The purpose of this study was to develop a smoked cocaine drug discrimination procedure in humans to test the effects of gabapentin maintenance on the discriminative stimulus, subjective, cognitive and cardiovascular effects of smoked cocaine. Eight male, nontreatment-seeking, cocaine-dependent volunteers, residing on an inpatient research unit for 47 days completed a within-subjects, counter-balanced design. Participants learned to discriminate between cocaine (25 mg) and placebo, and once the criterion for discrimination was met, smoked cocaine dose-effect functions (0, 6, 12, 25 and 50 mg) were determined under three gabapentin maintenance conditions (0, 600 and 1200 mg/day po). The highest dose of gabapentin tested (1200 mg/day) decreased the discriminative stimulus effects of cocaine (6 mg), decreased cocaine craving by 41-53% following cocaine administration (6 and 12 mg), and increased heart rate following either placebo or cocaine (12 mg) administration. Gabapentin did not significantly affect psychomotor task performance or the subjective effects of cocaine. Although the direction of gabapentin's effects was appropriate for a potential treatment medication, i.e., a decrease in cocaine-elicited craving and a decrease in cocaine's discriminative stimulus effects, these effects were limited to low doses of cocaine. The results suggest gabapentin may not produce effects sufficiently robust to be clinically useful, at least at this dose regimen.

A medication screening trial evaluation of reserpine, gabapentin and lamotrigine pharmacotherapy of cocaine dependence

AIMS

To conduct a preliminary evaluation of the safety and efficacy of reserpine, gabapentin or lamotrigine versus an unmatched placebo control as a treatment for cocaine dependence.

DESIGN

A 10-week out-patient study using the Cocaine Rapid Efficacy and Safety Trial (CREST) study design.

SETTING

The study was conducted at the Cincinnati Medication Development Research Unit (MDRU).

PARTICIPANTS

Participants met Diagnostic and Statistical Manual version IV (DSM-IV) criteria for cocaine dependence. Sixty participants were enrolled, with 50 participants completing the final study measures.

INTERVENTION

The targeted daily doses of medication were reserpine 0.5 mg, gabapentin 1800 mg and lamotrigine 150 mg. All participants received 1 hour of manualized individual cognitive behavioral therapy on a weekly basis.

MEASUREMENTS

Primary outcome measures of efficacy included urine benzoylecgonine (BE) level, Cocaine Clinical Global Impression scale--observer and self-report of cocaine use. Safety measures included adverse events, electrocardiograms (ECGs), vital signs and laboratory tests.

FINDINGS

Subjective measures of cocaine dependence indicated significant improvement for all study groups. Urine BE results indicated a significant improvement for the reserpine group (P < 0.05) and non-significant changes for the other study groups. No pattern of physical or laboratory abnormalities attributable to treatment with any of the medications was identified. There were three serious adverse events reported, none of which were related to study procedures. The medications appeared to be tolerated well.

CONCLUSIONS

The present findings suggest that reserpine may be worthy of further study as a cocaine dependence treatment.

Gabapentin maintenance decreases smoked cocaine-related subjective effects, but not self-administration by humans

Data from research with laboratory animals indicate that cocaine self-administration can be reduced by lambda-aminobutyric acid (GABA) agonists. Yet, the effectiveness of GABA agonists to decrease human cocaine self-administration has not been investigated under controlled laboratory conditions. The purpose of this study was to assess the effects of gabapentin, a GABA agonist, on cocaine-related behaviors, including self-administration, in human research participants under controlled laboratory conditions. During this 48-day double-blind, crossover design study, the effects of gabapentin (0, 600, and 1200 mg/d) maintenance on response to cocaine (0, 12, 25, and 50 mg) were investigated in seven cocaine abusers. Active cocaine significantly increased choice to self-administer cocaine, subjective-effect ratings (e.g., "Good Drug Effect"), blood pressure and heart rate (HR). Gabapentin did not reduce cocaine choice or cardiovascular measures, but it did decrease some subjective effects of cocaine (e.g., "Good Drug Effect" and "Anxious"). These data suggest that the cocaine-gabapentin combination was well-tolerated, and because some cocaine-related subjective effects were reduced by maintenance on relatively low gabapentin doses, future studies should test higher gabapentin doses.

Reinforcing versus anticonvulsant drugs: effects on intracranial self-stimulation rate-frequency M50 indices

Drugs of abuse, such as amphetamine and morphine, produce reward-related shifts on intracranial self-stimulation (ICSS) thresholds. The facilitatory effects on ICSS thresholds of drugs that act through the GABAergic system, however, are reported to be attributed to their antiseizure and anticonvulsant effects, rather than their reinforcing effects. Using a rate-frequency ICSS paradigm, we examined the effects of amphetamine (a reinforcing drug of abuse that acts via the catecholaminergic system), pentobarbital (a GABA(A) receptor agonist and reinforcing barbiturate with anticonvulsant properties), and gabapentin (a nonspecific GABAergic agonist and anticonvulsant with low abuse potential) on ICSS M(50) indices. All three doses of amphetamine (0.5, 1.0, and 2.0 mg/kg) and pentobarbital (2.5, 5.0, and 10.0 mg/kg) significantly lowered rate-frequency M(50) values. Gabapentin, on the other hand, significantly raised rate-frequency M(50) values, albeit only at the highest dose administered (30 mg/kg). Our results indicate that shifts in ICSS M(50) values produced by pentobarbital are associated with the reinforcing, not the anticonvulsant, effect of pentobarbital. These results are consistent with the view that there is a common system underlying the reinforcing effects of drugs and ICSS reinforcement, and suggest that the reinforcing and anticonvulsant effects of GABA agonists are dissociable.

Gabapentin and posttraumatic stress disorder

OBJECTIVE

To report the effects of gabapentin in a patient with concurrent depression and posttraumatic stress disorder (PTSD) and review the use of antiepileptic drugs (AEDs) in PTSD.

CASE SUMMARY

A 37-year-old Latin American woman was being treated for major depression and PTSD. While the depressive symptoms were in remission, she reported a significant reduction in the frequency of her flashbacks after gabapentin was added to venlafaxine. She did not receive any type of psychotherapy. The flashbacks recurred after she discontinued gabapentin.

DISCUSSION

While the improvement reported by the patient may have been related to a placebo effect or spontaneous recovery, treatment with gabapentin may have played a role in alleviating the flashbacks. Other published reports suggest that AEDs have a beneficial effect on some PTSD symptoms.

CONCLUSIONS

AEDs may be of some therapeutic value in patients with PTSD. Future controlled studies are warranted to investigate the effectiveness of these agents.

GABA(B) receptor agonists for the treatment of drug addiction: a review of recent findings

A growing preclinical and clinical literature suggests that GABA(B) receptor agonists promote abstinence and reduce the use of cocaine, heroin, alcohol and nicotine. The purpose of this paper is to critically review these data. GABA(B) receptor agonists, such as baclofen, appear to reduce the reinforcing effects of abused drugs in animal models under multiple experimental procedures. This occurs at doses that have little effect on responding for other positive reinforcers such as food or water. We review evidence that these potential therapeutic effects may be mediated by modulation of mesolimbic dopamine neurons. This review also examines the preliminary clinical data from studies of the efficacy of baclofen for treatment of cocaine, alcohol, and nicotine dependence. We suggest that these preliminary data provide a rationale for conducting more systematic studies of the effects of GABA(B) receptor agonists as treatment for drug abuse. This line of research may also improve our understanding of the neurochemical mechanisms underlying the drug dependence process.

Maximizing life's potentials in AIDS: a psychopharmacologic update

Psychiatric factors play a major role in the AIDS pandemic. They have an impact on transmission, morbidity, coping, adherence, and quality of life and of death. Substance-related disorders are associated with HIV transmission through needle sharing, sexual transmission, exchange of sex for drugs, and perinatal transmission. Persons with AIDS have a high prevalence of substance-related disorders, mood disorders, dementia, mania, and delirium. Persons with AIDS require complex medications, including combination antiretroviral therapy and prophylaxis and treatment for opportunistic infections and cancers. Recognition and treatment of distressing symptoms can maximize life's potentials and enhance adherence with risk prevention and with care. We describe an integrated approach to the use of psychotropic medications in the care of persons with AIDS. With the new antiretroviral therapies available, psychotropic medications can be helpful in alleviating distressing symptoms, promoting less risk taking, and adhering to complex medical care. The intricacies and complexities of new medical and psychopharmacological issues are delineated in order to enable caregivers help persons with AIDS to maximize life's potentials.

A case of sustained massive gabapentin overdose without serious side effects

Gabapentin is an antiepileptic agent that is indicated for use as adjunctive therapy for partial seizures. It has a relatively benign side effect profile, but little data exists on massive overdoses with this agent. The authors present a case of a patient who received a massive overdose of this agent but suffered no clinically significant toxicity.

Nonepileptic uses of gabapentin

For decades, antiepileptic drugs (AEDs) have been used to treat a variety of nonepileptic conditions such as chronic pain, psychiatric disorders, and movement disorders. As indicated by recent published reports, gabapentin, a relatively new AED, is useful for treating a wide range of neurologic and psychiatric conditions. Although its exact mechanism of action has yet to be determined, gabapentin is likely to have multiple effects. Unlike conventional AEDs used to treat nonepileptic disorders (e.g., carbamazepine, phenytoin, valproate) gabapentin offers the advantages of low toxicity and a favorable side-effect profile. The largest area of nonepileptic use of gabapentin is neuropathic pain, in which it has demonstrated efficacy in treatment of postherpetic neuralgia, diabetic neuropathy, and trigeminal neuralgia. It has also been reported effective as therapy for several psychiatric disorders, most notably bipolar disorder. In addition, review of the published literature reveals the usefulness of gabapentin in movement disorders, migraine prophylaxis, and cocaine dependence. Future clinical studies will provide further insight into the range of conditions for which gabapentin is effective.

Gabapentin: a review of published experience in the treatment of bipolar disorder and other psychiatric conditions

Successful therapy with valproate and carbamazepine in patients with psychiatric disorders led to investigation of other anticonvulsants for similar indications. Gabapentin is a relatively new anticonvulsant being investigated for potential use in the treatment of bipolar disorder (BD), anxiety disorders, behavioral dyscontrol, and substance use disorders. Its favorable side effect profile, absence of the need for therapeutic drug monitoring, and minimal drug interactions give gabapentin a potential role in these indications. Computer searches of the biomedical literature were undertaken to identify all pertinent case reports, case series, and studies of the drug as monotherapy or adjunctive therapy for BD; 10 reports were retrieved. In the treatment of various anxiety disorders, one study, one case report, and one case series were identified. At least one case series described gabapentin therapy for alcohol withdrawal and one case report of the drug for agitation associated with dementia. Published, well-designed studies evaluating the agent's effectiveness as monotherapy for BD are lacking. Its benefit as an adjunctive treatment with other mood stabilizers is also unestablished. Data regarding its efficacy in the treatment of anxiety disorders or manifestations of substance abuse are limited. These areas may deserve further investigation.

Gabapentin modifies extracellular opioid peptide content in amygdala: a microdialysis study

Opioid peptide release was monitored in the amygdala and hippocampus of freely moving rats following a single oral administration of gabapentin using microdialysis. Extracellular opioid peptide levels were elevated above basal levels in the amygdala within the first 60 (54%) and 90 min (68%) after gabapentin administration. Levels returned to basal conditions 120 min following the treatment. No significant changes were detected in the hippocampus. The majority of immunoreactive material recovered from the amygdala following gabapentin administration was identified as Leu-enkephalin and Met-enkephalin by high performance liquid chromatography (HPLC) analysis. It is proposed that the enhanced opioid peptide release in the amygdala induced by gabapentin might be involved with the antiepileptic effects as well as with some adverse events produced by this drug.

An update on GABAA receptors

Recent advances in molecular biology and complementary information derived from neuropharmacology, biochemistry and behavior have dramatically increased our understanding of various aspects of GABAA receptors. These studies have revealed that the GABAA receptor is derived from various subunits such as alpha1-alpha6, beta1-beta3, gamma1-gamma3, delta, epsilon, pi, and rho1-3. Furthermore, two additional subunits (beta4, gamma4) of GABAA receptors in chick brain, and five isoforms of the rho-subunit in the retina of white perch (Roccus americana) have been identified. Various techniques such as mutation, gene knockout and inhibition of GABAA receptor subunits by antisense oligodeoxynucleotides have been used to establish the physiological/pharmacological significance of the GABAA receptor subunits and their native receptor assemblies in vivo. Radioligand binding to the immunoprecipitated receptors, co-localization studies using immunoaffinity chromatography and immunocytochemistry techniques have been utilized to establish the composition and pharmacology of native GABAA receptor assemblies. Partial agonists of GABAA receptors are being developed as anxiolytics which have fewer and less severe side effects as compared to conventional benzodiazepines because of their lower efficacy and better selectivity for the GABAA receptor subtypes. The subunit requirement of various drugs such as anxiolytics, anticonvulsants, general anesthetics, barbiturates, ethanol and neurosteroids, which are known to elicit at least some of their pharmacological effects via the GABAA receptors, have been investigated during the last few years so as to understand their exact mechanism of action. Furthermore, the molecular determinants of clinically important drug-targets have been investigated. These aspects of GABAA receptors have been discussed in detail in this review article.

A novel strategy for the treatment of cocaine addiction

Cocaine's addictive liability has been linked to its pharmacologic actions on mesotelencephalic dopamine (DA) reinforcement/reward pathways in the central nervous system (CNS). Dopaminergic transmission within these pathways is modulated by gamma-aminobutyric acid (GABA). With this knowledge, we examined the utility of gamma vinylGABA (GVG), a selective and irreversible inhibitor of GABA-transaminase (GABA-T) known to potentiate GABAergic inhibition, to alter cocaine's biochemical effects as well as its effects on behaviors associated with these biochemical changes. GVG significantly attenuated cocaine-induced increases in neostriatal synaptic DA in the non-human primate (baboon) brain as assessed by positron emission tomography (PET) and abolished both the expression and acquisition of cocaine-induced conditioned place preference (CPP). It had no effect on CPP for a food reward, the delivery of cocaine to the brain or locomotor activity. These findings suggest the possible therapeutic utility in cocaine addiction of a pharmacologic strategy targeted at the GABAergic neurotransmitter system, a system distinct from but functionally linked to the DA mesotelencephalic reward/reinforcement system. However, rather than targeting the GABA receptor complex with a direct GABA agonist, this novel approach with GVG takes advantage of the prolonged effects of an irreversible enzyme inhibitor that raises endogenous GABA levels without the addictive liability associated with GABA agonists acting directly at the receptor itself. Human trials with GVG are currently being developed to directly examine the utility of this novel strategy for the treatment of cocaine addiction.