Profiles of pregabalin and gabapentin abuse by postmortem toxicology

Oxycodone-induced tolerance to respiratory depression: reversal by ethanol, pregabalin and protein kinase C inhibition

BACKGROUND AND PURPOSE

Oxycodone, a prescription opioid, is a major drug of abuse, especially in the USA, and contributes significantly to opioid overdose deaths each year. Overdose deaths result primarily from respiratory depression. We have studied respiratory depression by oxycodone and have characterized how tolerance develops on prolonged exposure to the drug. We have investigated the role of PKC in maintaining tolerance and have examined whether ethanol or pregabalin reverses oxycodone-induced tolerance.

EXPERIMENTAL APPROACH

Respiration was measured in male CD-1 mice by whole-body plethysmography. Mice were preinjected with oxycodone then implanted with mini-pumps (s.c.) delivering 20, 45 or 120 mg·kg-1 ·day-1 oxycodone for 6 days and subsequently challenged with oxycodone (3 mg·kg-1 , i.p.) or morphine (10 mg·kg-1 , i.p.) to assess the level of tolerance.

KEY RESULTS

Oxycodone-treated mice developed tolerance to oxycodone and cross tolerance to morphine-induced respiratory depression. Tolerance was less with 20 mg·kg-1 ·day-1 than with 45 or 120 mg·kg-1 ·day-1 oxycodone treatment. At doses that do not depress respiration, ethanol (0.3 g·kg-1 ), pregabalin (20 mg·kg-1 ) and calphostin C (45 μg·kg-1 ) all reversed oxycodone-induced tolerance resulting in significant respiratory depression. Reversal of tolerance was less in mice treated with oxycodone (120 mg·kg-1 ·day-1 ). In mice receiving ethanol and calphostin C or ethanol and pregabalin, there was no greater reversal of tolerance than seen with either drug alone.

CONCLUSION AND IMPLICATIONS

These data suggest that oxycodone-induced tolerance is mediated by PKC and that reversal of tolerance by ethanol or pregabalin may be a contributory factor in oxycodone overdose deaths.

Prevalence of gabapentin in drug overdose postmortem toxicology testing results

BACKGROUND

The goal of this study was to establish and compare baseline data on the prevalence of gabapentin identified through postmortem toxicology testing among drug overdose decedents in several geographically diverse states/jurisdictions with differing levels of drug overdose fatality burdens in 2015.

METHODS

Death certificates and postmortem toxicology result reports from five U.S. jurisdictions were used to identify residents who died from drug overdoses in year 2015 and to calculate prevalence rates of gabapentin in postmortem toxicology by jurisdiction.

RESULTS

On average, 22% of all drug overdose decedents in our study tested positive for gabapentin. The percentage of gabapentin-positive overdose deaths varied significantly among jurisdictions: 4% in Northeast Tennessee, 7% in Maricopa County, 15% in West Virginia, 20% in North Carolina, and 41% in Kentucky (p < 0.0001). Among the drug overdose decedents who tested positive for opioids (including heroin), 26% also tested positive for gabapentin, with significant variation among states/jurisdictions (p < 0.0001). There was a significant difference in the gender distribution among drug overdose decedents who tested positive for gabapentin (46% male) vs. those who tested negative for gabapentin (65% male) (p < 0.0001). In Kentucky, gabapentin was listed as a contributing drug on the death certificate in 40% of the overdose deaths with gabapentin-positive toxicology; in North Carolina this percentage was 57%.

CONCLUSIONS

Routine gabapentin postmortem testing and linking of death certificate, medical examiner, coroner, toxicology, and prescription history data will provide more reliable information on the extent of gabapentin misuse, diversion, and implications for clinical care.

Addiction-related interactions of pregabalin with morphine in mice and humans: reinforcing and inhibiting effects

The gabapentinoid pregabalin is a rapid-acting anxiolytic and analgesic, possibly suitable in supervised opioid detoxification. However, clinicians have been cautious in using it because of its unknown addictive risk and rising number of mortalities after pregabalin self-medication in opioid abusers. Here, we studied interactions of pregabalin and morphine on reward functions of the dopamine system in mice and the efficacy of pregabalin on withdrawal in opioid addicts. After the treatment of mice with pregabalin and morphine, we used electrophysiology to study neuroplasticity in midbrain slices, self-administration and conditioned place preference tests to investigate the rewarding potential of pregabalin and naloxone-precipitated morphine withdrawal to evaluate opioid withdrawal symptoms. Further, we ran a pilot single-blind, randomized, controlled trial (34 heroin addicts) to evaluate the efficacy and safety of pregabalin in the treatment of opioid withdrawal syndrome. Pregabalin alone did not induce glutamate receptor neuroplasticity of dopamine neurons in the ventral tegmental area, but pre-treatment with pregabalin suppressed morphine-induced neuroplasticity, hyperlocomotion and morphine self-administration. Pregabalin administration after chronic morphine exposure failed to induce any rewarding effects. Instead, pregabalin suppressed withdrawal symptoms in both morphine-treated mice and opioid addicts and was well tolerated. Intriguingly, pregabalin administration after a low dose of morphine strongly facilitated ventral tegmental area neuroplasticity and led to increased conditioned place preference. Pregabalin appears to have the efficacy to counteract both reinforcing and withdrawal effects of opioids, but it also has a potentiating effect when given to mice with existing opioid levels.

Utilization of gabapentin by people in treatment for substance use disorders in Belgium (2011-2014): a cross-sectional study

Background

Although gabapentin has been licensed in the European Union only for neuropathic pain and epilepsy for patients who have partial seizures, it has also been prescribed in treatment for substance use disorders. Many studies report the potential risk of abuse of gabapentin by people with substance use disorders. The objective of this paper is to determine if people who have been in treatment for substance use disorders bought gabapentin in a time span that could indicate consumption at a dose that exceeded the maximum approved dose of 3600 mg/day.

Methods

This analysis is the result of an observational cross-sectional descriptive study with matching. Two datasets were used and linked at individual level. Subjects were selected based on their first registration in the database of the Treatment Demand Indicator (TDI) between 2011 and 2014, without any exclusion criteria concerning nationality or age. Through linkage with the database of the InterMutualistic Agency (IMA) information on health service use and medication use was determined. In addition, each subject was matched on age, sex and place of residence to four comparators from the general population who were not in specialized treatment. The prevalence of gabapentin purchases in the period between 2008 and 2014 for both populations were compared. Quantification of the amount of gabapentin between two consecutive purchases was used as a proxy for potential abuse.

Results

Out of 30,905 patients in treatment for substance use disorders 2.7% had bought at least once gabapentin in a public pharmacy or received it from a hospital pharmacy, compared to 0.7% in the comparison group (n = 122,142). In both populations, more than half of the patients bought only once or twice gabapentin and about 10.0% bought at least once gabapentin in a time span that could indicate potential abuse. A limitation of the study is that it is only based on reimbursed medication without clinical information.

Conclusion

Through the linkage of the TDI-database and the database of the Belgian health insurance companies, no evidence was found for regular abuse of prescribed gabapentin in Belgium by people in treatment for substance use disorders.

Pregabalin Misuse and Abuse: A Scoping Review of Extant Literature

Prescribing of pregabalin is increasing worldwide with public health concerns centering on misuse and abuse of prescribed and diverted pregabalin. To describe and map what is known about misuse and abuse of pregabalin, a scoping review of available published literature was undertaken. A scoping review methodology was used to identify and map available literature on misuse and abuse of prescribed and diverted pregabalin. Four themes emerged on the misuse and abuse of pregabalin: (a) abuse potential, (b) prevalence of abuse, (c) risk and predisposition, and (d) consequences of abuse. Fifty-four records were reviewed and charted. Of note was the dearth of research on the topic prior to 2005, with increased interest in pregabalin abuse potential from 2010 onward. Available literature supports concern around abuse potential of pregabalin, especially among patients with a history of substance abuse. Prescribers should adopt more rational prescribing.

Non-medical use of psychoactive prescription drugs is associated with fatal poisoning

AIMS

The aims of this study were to estimate the prevalence and predictors of non-medical substance use, and to assess the association between non-medical substance use and fatal poisoning or history of drug abuse in Finland.

DESIGN AND SETTING

Retrospective cohort study of all medico-legally investigated death cases in Finland. The postmortem toxicology database was linked together with the register on reimbursed prescription medicines.

PARTICIPANTS AND CASES

All postmortem cases between 2011 and 2013 positive for one or more of the following drugs: oxycodone, fentanyl, tramadol, clonazepam, gabapentin, pregabalin, tizanidine, olanzapine, quetiapine, risperidone, alprazolam, zolpidem, mirtazapine and bupropion, n = 2974.

MEASUREMENTS

Non-medical use of substance was the outcome variable. Predictors were the following: gender, residence at the time of death, place of death, blood alcohol concentration, age, drug abuse, number of prescriptions of any psychoactive drugs in last year and proportion of prescriptions issued by psychiatrist in last year.

FINDINGS

In 50.4% of the studied cases, at least one drug was detected without a prescription. Clonazepam, alprazolam and tramadol were the most prevalent non-medical findings in these cases (6.6, 6.1 and 5.6%, respectively). The risk of non-medical use of prescription drugs was especially high in cases with history of drug abuse (88.5%) and in fatal poisonings (71.0%). The proportion of non-medical use of the studied substances varied between 5.9% [95% confidence interval (CI) = 3.1-10.1%)] for risperidone and 55.7% for fentanyl (95% CI = 44.1-66.9%). Valid prescription for one or more of any psychoactive drug was associated with lower odds for non-medical use of the studied substances. Additionally, the higher the proportion of psychoactive drugs prescribed by a psychiatrist, the lower the probability of non-medical use.

CONCLUSIONS

Non-prescribed psychoactive drugs are found commonly at postmortem in drug poisoning deaths in Finland, with history of drug abuse being a major contributing factor.

GC-MS/MS detects potential pregabalin abuse in susceptible subjects' hair

Pregabalin, a GABA analogue, binds to the alpha 2 delta subunit of voltage-dependent calcium channels. It is recognised as efficacious in pathologies such as epilepsy, neuropathic pain, and anxiety disorders. Since pregabalin prescriptions have increased worldwide, reports of its abuse have been accumulating, mainly in patients with opioid abuse disorders. The present study investigated potential pregabalin abuse by means of hair analysis, a matrix that provides valuable retrospective information. Half of the pool of 280 susceptible patients had been occasional drug users and were being monitored for driving licence renewals. The other 140 patients had a history of opiate dependency and were monitored to assess compliance with methadone therapy. In view of determining pregabalin in hair samples, it was extracted in methanol, successfully derivatised to give the ethyl chloroformate derivative, and finally pregabalin was analysed by gas chromatography-tandem mass spectrometry. Selectivity, linearity, limit of detection, limit of quantification, recovery, intra- and inter-day precision, and accuracy of the quantification procedure were appraised. Pregabalin limits of detection and quantification were 30 pg/mg and 50 pg/mg, respectively. We found 10.7% of hair samples from methadone patients and 4.29% from occasional drug users were positive to pregabalin without medical prescription. The mean pregabalin concentration in hair was higher than in consumers with medical indications (1.45 ng/mg vs 0.74 ng/mg). These results suggest that pregabalin possesses a significant abuse potential particularly among individuals attending opiate dependence services and that pregabalin abuse is a serious emerging issue, which should be carefully monitored.

Responding to New Psychoactive Substances in the European Union: Early Warning, Risk Assessment, and Control Measures

New psychoactive substances (NPS) are drugs that are not controlled by the United Nations international drug control conventions of 1961 and 1971 but that may pose similar threats to public health. Many of them are traded as "legal" replacements to controlled drugs such as cannabis, heroin, benzodiazepines, cocaine, amphetamines, and 3,4-methylenedioxymethamphetamine (MDMA). Driven by globalization, there has been a large increase in the availability and, subsequently, harms caused by these substances over the last decade in Europe. The European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) is monitoring more than 670 NPS that have appeared on Europe's drug market in the last 20 years, of which almost 90% have appeared in the last decade. While some recent policy responses have been successful in reducing availability and sales of these substances in some settings - such as "legal highs" and "research chemicals" sold openly in the high street and online - and there are signs that growth in the market is slowing, new challenges have emerged. This includes monitoring a growing number of highly potent substances - including 179 synthetic cannabinoid receptor agonists and 28 fentanils - that can pose a high risk of life-threatening poisoning to users and can cause explosive outbreaks. This chapter briefly traces the origins of NPS, provides an overview of the situation in Europe, and discusses the work of the EMCDDA as part of a legal framework of early warning, risk assessment, and control measures that allows the European Union to rapidly detect, assess, and respond to public health and social threats caused by these substances.

Gabapentin for the treatment of alcohol use disorder

INTRODUCTION

Alcohol misuse is the fifth leading risk factor for premature death and disability worldwide. Fewer than 10% of afflicted Americans receive pharmacological treatment for alcohol use disorder. Gabapentin is a calcium channel GABAergic modulator that is widely used for pain. Studies showing reduced drinking and decreased craving and alcohol-related disturbances in sleep and affect in the months following alcohol cessation suggest therapeutic potential for alcohol use disorder. Areas covered: Human laboratory and clinical studies assessing gabapentin for alcohol use disorder are reviewed. Data were obtained by searching for English peer-reviewed articles on PubMed, reference lists of identified articles, and trials registered on clinicaltrials.gov. Additionally, the mechanism of action of gabapentin specific to alcohol use disorder, and studies of gabapentin for alcohol withdrawal and non-alcohol substance use disorders are summarized. Expert opinion: Alcohol use disorder represents a challenge and large, unmet medical need. Evidence from single-site studies lend support to the safety and efficacy of gabapentin as a novel treatment for alcohol use disorder, with unique benefits for alcohol-related insomnia and negative affect, relative to available treatments. Proprietary gabapentin delivery systems may open a path to pivotal trials and registration of gabapentin as a novel treatment for alcohol use disorder.

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.

Pregabalin Use Among Users of Illicit Drugs: A Cross-Sectional Survey in Southern Germany

BACKGROUND

The antiepileptic drug pregabalin is one of the best-selling pharmaceutical products worldwide. There are increasing concerns about its potential for misuse and dependence especially among patients with former or current substance use disorders (SUDs).

OBJECTIVE

Our objective was to clarify the extent and pattern of pregabalin use as well as motives and predictors in this population.

METHODS

We conducted a cross-sectional study with patients on a detoxification ward for illicit drugs at the Center for Psychiatry, Südwürttemberg, Ravensburg in southern Germany from August 2012 until July 2013. We used an extensive questionnaire, part of the Structured Clinical Interview for DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition) Axis I Disorders (SCID-I) and urine samples.

RESULTS

Of the 253 participating patients, 56% had used pregabalin at least once. Of these, 92% had acquired it at least in part from illegal sources. The main motives for the use of pregabalin were the attenuation of opioid withdrawal symptoms, the augmentation of other psychotropic substances, and the psychotropic effects of pregabalin itself. Predictors for pregabalin use were opioid and sedative use as well as younger age. The criteria of dependency according to DSM-IV was met by 11% of pregabalin users and 13% of urine samples were positive for pregabalin.

CONCLUSIONS

Use of pregabalin is common among users of illicit drugs in large parts of southern Germany, with motives for use, acquisition, and mode of use suggesting misuse. The mode of use, especially intake of high doses and concomitant use of other drugs, poses a serious risk to this population, including the development of dependency.

Risk to heroin users of polydrug use of pregabalin or gabapentin

AIM

To examine the risk to heroin users of also using gabapentin or pregabalin (gabapentoids).

DESIGN

Multi-disciplinary study: we (a) examined trends in drug-related deaths and gabapentoid prescription data in England and Wales to test for evidence that any increase in deaths mentioning gabapentin or pregabalin is associated with trends in gabapentoid prescribing and is concomitant with opioid use; (b) interviewed people with a history of heroin use about their polydrug use involving gabapentin and pregabalin; and (c) studied the respiratory depressant effects of pregabalin in the absence and presence of morphine in mice to determine whether concomitant exposure increased the degree of respiratory depression observed.

SETTING

England and Wales.

PARTICIPANTS

Interviews were conducted with 30 participants (19 males, 11 female).

MEASUREMENTS

(a) Office of National Statistics drug-related deaths from 1 January 2004 to 31 December 2015 that mention both an opioid and pregabalin or gabapentin; (b) subjective views on the availability, use, interactions and effects of polydrug use involving pregabalin and gabapentin; and (c) rate and depth of respiration.

RESULTS

Pregabalin and gabapentin prescriptions increased approximately 24% per year from 1 million in 2004 to 10.5 million in 2015. The number of deaths involving gabapentoids increased from fewer than one per year prior to 2009 to 137 in 2015; 79% of these deaths also involved opioids. The increase in deaths was correlated highly with the increase in prescribing (correlation coefficient 0.94; 5% increase in deaths per 100 000 increase in prescriptions). Heroin users described pregabalin as easy to obtain. They suggested that the combination of heroin and pregabalin reinforced the effects of heroin but were concerned it induced 'blackouts' and increased the risk of overdose. In mice, a low dose of S-pregabalin (20 mg/kg) that did not itself depress respiration reversed tolerance to morphine depression of respiration (resulting in 35% depression of respiration, P < 0.05), whereas a high dose of S-pregabalin (200 mg/kg) alone depressed respiration and this effect summated with that of morphine.

CONCLUSIONS

For heroin users, the combination of opioids with gabapentin or pregabalin potentially increases the risk of acute overdose death through either reversal of tolerance or an additive effect of the drugs to depress respiration.

Benzodiazepine, z-drug and pregabalin prescriptions and mortality among patients in opioid maintenance treatment-A nation-wide register-based open cohort study

BACKGROUND

Use of sedatives may increase risk of death in opioid users. The aim of the study was to assess whether prescription of sedatives may be associated with mortality in patients in opioid maintenance treatment.

METHODS

This retrospective register-based open cohort study included nation-wide register data including all individuals who were dispensed methadone or buprenorphine as opioid maintenance treatment for opioid dependence between July, 2005 and December, 2012 (N=4501). Outcome variables were overdose mortality and non-overdose mortality, respectively. Extended Cox regression analyses examined associations between type of sedative prescriptions and death, controlling for sex, age, previous overdoses and suicide attempts, psychiatric in-patient treatment and opioid maintenance treatment status. Opioid maintenance was assumed to last for 90days (or 30days in a sensitivity analysis) after the last methadone or buprenorphine prescription.

RESULTS

Benzodiazepine prescriptions were associated with non-overdose death (HR: 2.02, 95% CI: 1.29-3.18) but not significantly associated with overdose death (1.49, 0.97-2.29). Z-drug (1.60, 1.07-2.39) and pregabalin prescriptions (2.82, 1.79-4.43) were associated with overdose death. In the sensitivity analysis, all categories of sedatives, including benzodiazepines, were significantly associated with overdose death.

CONCLUSIONS

Caution is advised when prescribing sedative drugs, including benzodiazepines, z-drugs and pregabalin, to patients in opioid maintenance treatment.

Review about gabapentin misuse, interactions, contraindications and side effects

The current work is targeted to review the risks of gabapentin misuse, its potential interactions with other drugs, side effects and use contraindications. This review consists of a total of 99 biographical references (from the year 1983 to 2016). A publication search of PubMed was performed from January 1983 to December 2016. It included animal studies, clinical studies, case studies and reviews related to gabapentin misuse, potential interactions, side effects and use contraindications. The search terms were gabapentin, anticonvulsant and antiepileptic. In general, it seems that gabapentin has risks of being misused based on the increased level of prescriptions, related fatalities, recreational misuse and higher doses of self-administration. The main reasons for gabapentin misuse are as follows: getting high, alleviating opioid withdrawal symptoms and potentiating methadone effects. Some of the main substances that interact with gabapentin are morphine, caffeine, losartan, ethacrynic acid, phenytoin, mefloquine and magnesium oxide. Some of the side effects caused by gabapentin are teratogenicity, hypoventilation, respiratory failure and myopathy. Finally, reports in general contraindicate the use of gabapentin in conditions such as myasthenia gravis and myoclonus.

Nonmedical Use of Antihistaminergic Anxiolytics and Other Prescription Drugs among Persons with Opioid Dependence

Background. Nonmedical prescription drug use (NMPDU) is an increasing problem, insufficiently studied among people in opioid maintenance treatment (OMT). This study investigates the prevalence of and factors associated with NMPDU for drug classes insufficiently described in opioid-dependent populations, including antihistaminergic anxiolytics and central stimulants. Methods. Study participants were recruited at two OMT clinics in Malmo, Sweden, between October 2014 and December 2015 (N = 73) and interviewed about their use, motivations for use, and acquisition and administration of prescription drugs. Results. The majority of the sample reported lifetime NMPDU: 60% for benzodiazepine-like hypnotics (z-drugs), 21% for pregabalin, 19% for stimulants, and 12%-15% for antihistaminergic anxiolytics. Lower age was associated with nonmedical benzodiazepine use (Adjusted Odds Ratio = 0.89; 95% Confidence Interval = 0.82-0.97). Illicit acquisition was reported by 61% of people using z-drugs, 46% of people using pregabalin, and 38% of people using prescription stimulants, but only by 6-10% of people using antihistaminergic anxiolytics. Conclusions. The substantial nonmedical use of pregabalin, z-drugs, and prescription stimulants found in this study suggests that clinicians should prescribe these drugs with great caution. Nonmedical use of antihistaminergic anxiolytics does not seem to be a clinical issue among people in OMT in a Swedish setting, but we propose future studies to monitor their use.

Pregabalin for the Treatment of Drug and Alcohol Withdrawal Symptoms: A Comprehensive Review

Treatments for physical dependence and associated withdrawal symptoms following the abrupt discontinuation of prescription drugs (such as opioids and benzodiazepines), nicotine, alcohol, and cannabinoids are available, but there is still a need for new and more effective therapies. This review examines evidence supporting the potential use of pregabalin, an α2δ voltage-gated calcium channel subunit ligand, for the treatment of physical dependence and associated withdrawal symptoms. A literature search of the MEDLINE and Cochrane Library databases up to and including 11 December 2015 was conducted. The search term used was '(dependence OR withdrawal) AND pregabalin'. No other date limits were set and no language restrictions were applied. Works cited in identified articles were cross-referenced and personal archives of references also searched. Articles were included based on the expert opinions of the authors. There is limited evidence supporting the role of pregabalin for the treatment of physical dependence and accompanying withdrawal symptoms associated with opioids, benzodiazepines, nicotine, cannabinoids, and alcohol, although data from randomized controlled studies are sparse. However, the current evidence is promising and provides a platform for future studies, including appropriate randomized, placebo- and/or comparator-controlled studies, to further explore the efficacy and safety of pregabalin for the treatment of withdrawal symptoms. Given the potential for pregabalin misuse or abuse, particularly in individuals with a previous history of substance abuse, clinicians should exercise caution when using pregabalin in this patient population.

Gabapentin, Pregabalin and Vigabatrin Quantification in Human Serum by GC-MS After Hexyl Chloroformate Derivatization

A simple, sensitive and robust method for simultaneous determination of antiepileptic drugs (gabapentin, pregabalin and vigabatrin) in human serum using GC-MS was developed and validated for clinical toxicology purposes. This method employs an emerging class of derivatization agents - alkyl chloroformates allowing the efficient and rapid derivatization of both the amino and carboxylic groups of the tested antiepileptic drugs within seconds. The derivatization protocol was optimized using the Design of Experiment statistical methodology, and the entire sample preparation requires less than 5 min. Linear calibration curves were obtained in the concentration range from 0.5 to 50.0 mg/L, with adequate accuracy (97.9-109.3%) and precision (<12.1%). The method was successfully applied to quantification of selected γ-aminobutyric acid analogs in the serum of patients in both therapeutic and toxic concentration ranges.

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.

Fatal toxicity index of medicinal drugs based on a comprehensive toxicology database

The fatal toxicity index (FTI) is the absolute number of fatal poisonings caused by a particular drug divided by its consumption figure. Consequently, it is a useful measure in evaluating toxicity of the drug and its relevance in fatal poisonings. In this study, we assessed the FTI of medicinal drugs in 3 years (2005, 2009, and 2013) in Finland. As the measure of drug consumption, we used the number of defined daily doses (DDD) per population in each year. There were 70 medicinal drugs in Finland for which the mean FTI expressed as the number of deaths per million DDD over the three study years was higher or equal to 0.1. The Anatomical Therapeutic Chemical (ATC) classification system was used for the classification of the active ingredients of medicinal drugs according to the organ or system which they act on. Of these 70 drugs, 55 drugs (78.6 %) acted on the nervous system (denoted by ATC code N), 11 (15.7 %) on the cardiovascular system (C), three (4.3 %) on the alimentary tract and metabolism (A), and one (1.4 %) on the musculoskeletal system (M). The nervous system drugs consisted of 20 psycholeptics, (ATC code N05), 20 psychoanaleptics (N06), eight analgesics (N02), six antiepileptics (N03), and one other nervous system drug (N07). The highest individual FTIs were associated with the opioids methadone, dextropropoxyphene, oxycodone, tramadol, and morphine; the antipsychotics levomepromazine and chlorprothixene; and the antidepressants doxepin, amitriptyline, trimipramine, and bupropion. Buprenorphine was not included in the study, because most of the fatal buprenorphine poisonings were due to smuggled tablets. A clearly increasing trend in FTI was observed with pregabalin and possibly with bupropion, both drugs emerging as abused substances.

Antiepileptic use for epilepsy and nonepilepsy disorders: A population-based study (1998-2013)

OBJECTIVE

To examine the trends in antiepileptic drug (AED) use among individuals living in Manitoba with and without a history of epilepsy.

METHODS

Using data obtained from administrative health databases in Manitoba, we assessed the quarterly prevalence of AED use between 1998 and 2013 among individuals with and without a history of epilepsy using cross-sectional time series analysis.

RESULTS

Over the study period, the number of individuals prescribed AEDs increased more than 3-fold, from 8,883 to 27,246. The prevalence of AED use among patients with epilepsy increased by 3%, from 789.6 per 1,000 in 1998/1999 to 813.9 per 1,000 in 2012/2013 (p < 0.001 after 2006). In contrast, we observed a 210% increase in AED use among patients without epilepsy from 6.8 to 21.1 per 1,000 over the same period (p < 0.001). We observed a 55-fold rise in gabapentin use among patients without a seizure disorder (from 0.2 to 11.1 per 1,000; p < 0.001), while gabapentin use among those with epilepsy increased only 2-fold, from 21.6 to 41.3 per 1,000 (p < 0.001).

CONCLUSIONS

There has been a marked increase in the prevalence of AED users over the last 15 years, with a large shift towards the use of newer antiepileptic agents (primarily gabapentin) among those without epilepsy. Further research on the effect of these trends on health and economic outcomes will be of interest for clinicians and policymakers.

Abuse Potential of Pregabalin: A Systematic Review

BACKGROUND

Several case reports and epidemiological studies have raised concern about the abuse potential of pregabalin, the use of which has increased substantially over the last decade. Pregabalin is, in some cases, used for recreational purposes and it has incurred attention among drug abusers for causing euphoric and dissociative effects when taken in doses exceeding normal therapeutic dosages or used by alternative routes of administration, such as nasal insufflation or venous injection. The magnitude of the abuse potential and the mechanism behind it are not fully known.

OBJECTIVE

The aim of this study was to present a systematic review of the data concerning the abuse potential of pregabalin.

METHODS

We performed a systematic literature search and reviewed the preclinical, clinical and epidemiological data on the abuse potential of pregabalin.

RESULTS

We included preclinical (n = 17), clinical (n = 19) and epidemiological (n = 13) studies addressing the abuse potential of pregabalin. We also reviewed case reports (n = 9) concerning abuse of pregabalin. The preclinical studies indicated that pregabalin possesses modulatory effects on the GABA and glutamate systems, leaving room for an abuse potential. Further, clinical studies reported euphoria as a frequent side effect in patients treated with pregabalin. The majority of case reports concerning abuse of pregabalin involved patients with a history of substance abuse and, similarly, epidemiological studies found evidence of abuse, especially among opiate abusers.

CONCLUSIONS

Overall, the available literature suggests an important clinical abuse potential of pregabalin and prescribers should pay attention to signs of abuse, especially in patients with a history of substance abuse.

Pregabalin Has Analgesic, Ventilatory, and Cognitive Effects in Combination with Remifentanil

Background

Pregabalin is widely used perioperatively. The authors explored the effects of pregabalin, remifentanil, and their combination on experimental pain, ventilatory, and cognitive function.

Methods

In a randomized, double-blinded crossover study, 12 volunteers received (1) pregabalin + placebo, (2) placebo + remifentanil, (3) pregabalin + remifentanil, and (4) placebo + placebo. Pregabalin 150 mg/placebo was administered twice orally. After baseline, remifentanil/placebo was given as effect-site target-controlled infusion (TCI): 0.6, 1.2, and 2.4 ng/ml. Pain during cold pressor test was scored on visual analog scale (0 to 100 mm). Ventilation was measured by spirometry and cognition tested with Color-Word Interference and Rapid Information Processing tests.

Results

Pain intensity after placebo was (mean) 72 mm (95% CI, 62 to 83). Pregabalin reduced pain score by −10 mm (−14 to −7, P &lt; 0.001). Remifentanil had dose-dependent analgesic effect, reducing pain score by −47 mm (−54 to −39, P &lt; 0.001) on highest TCI level, whereas pregabalin + remifentanil exerted additive effect, reducing pain score by −57 mm (−64 to −50, P &lt; 0.001). Respiratory depression was potentiated by adding pregabalin to remifentanil; end-tidal carbon dioxide was 39.3 mmHg (37.2 to 41.3) with placebo, increased 1.8 mmHg (−0.9 to 4.6, P = 0.4) with pregabalin, 10.1 mmHg (4.9 to 15.4, P &lt; 0.001) with remifentanil, and 16.4 mmHg (11.3 to 21.5, P &lt; 0.001) with pregabalin + remifentanil on highest TCI level. The combination pregabalin + remifentanil, but not either drug alone, adversely affected all cognitive tests.

Conclusions

The combination of pregabalin and remifentanil had additive analgesic effects, pregabalin potentiated remifentanil ventilatory depression, and the combination adversely affected cognition. These results question the clinical benefit of the combination compared with higher doses of opioids.

Patterns of drug abuse among drug users with regular and irregular attendance for treatment as detected by comprehensive UHPLC-HR-TOF-MS

The most severe consequences of drug abuse include infectious diseases, overdoses, and drug-related deaths. As the range of toxicologically relevant compounds is continually changing due to the emergence of new psychoactive substances (NPS), laboratories are encountering analytical challenges. Current immunoassays are insufficient for determining the whole range of the drugs abused, and a broad-spectrum screening method is therefore needed. Here, the patterns of drug abuse in two groups of drug users were studied from urine samples using a comprehensive screening method based on high-resolution time-of-flight mass spectrometry. The two groups comprised drug abusers undergoing opioid maintenance treatment (OMT) or drug withdrawal therapy and routinely visiting a rehabilitation clinic, and drug abusers with irregular attendance at a harm reduction unit (HRU) and suspected of potential NPS abuse. Polydrug abuse was observed in both groups, but was more pronounced among the HRU subjects with a mean number of concurrent drugs per sample of 3.9, whereas among the regularly treated subjects the corresponding number was 2.1. NPS and pregabalin were more frequent among HRU subjects, and their abuse was always related to drug co-use. The most common drug combination for an HRU subject included amphetamine, cannabis, buprenorphine, benzodiazepine, and alpha-pyrrolidinovalerophenone. A typical set of drugs for treated subjects was buprenorphine, benzodiazepine, and occasionally amphetamine. Abuse of several concurrent drugs poses a higher risk of drug intoxication and a threat of premature termination of OMT. Since the subjects attending treatment used fewer concurrent drugs, this treatment could be valuable in reducing polydrug abuse.

Prescribing medical cannabis in Canada: Are we being too cautious?

There has been much recent discussion and debate surrounding cannabis in Canada, including the prescribing of medical cannabis for therapeutic purposes. Certain commentators - including the Canadian Medical Association (CMA) - have denounced the prescribing of cannabis for medical purposes due to a perceived lack of evidence related to the drug's efficacy, harms, and mechanism of action. In this commentary, we present arguments in favour of prescribing medical cannabis in Canada. We believe the anti-cannabis position taken by CMA and other commentators is not entirely evidence-based. Using the example of neuropathic pain, we present and summarize the clinical evidence surrounding smoked or vapourized cannabis, including recent evidence pertaining to the effectiveness of cannabis in comparison to existing standard pharmacotherapies for neuropathy. Further, we outline how the concerns expressed regarding cannabis' mechanism of action are inconsistent with current decision-making processes related to the prescribing of many common pharmaceuticals. Finally, we discuss potential secondary public health benefits of prescribing cannabis for pain-related disorders in Canada and North America.

An acute gabapentin fatality: a case report with postmortem concentrations

Gabapentin (GBP) (Neurontin®, Horizant®, Gralise®) is a widely prescribed medication used primarily for the treatment of epilepsy and neuropathic pain. GBP has a favorable adverse effect profile in therapeutic dosing with the most common reported effects being dizziness, fatigue, drowsiness, weight gain, and peripheral edema. Even with intentional GBP self-poisonings, serious effects are rare. A 47-year-old female was found dead at work with her daughter's bottle of GBP 600 mg. There were 26 tablets missing and the decedent's only known medication was hydrocodone/acetaminophen. Following initial detection by an alkaline drug screen (GC-MS), analysis utilizing specific liquid chromatography-mass spectrometry revealed an elevated postmortem GBP peripheral blood concentration of 37 mg/L, central blood 32 mg/L, liver 26 mg/kg, vitreous 32 mg/L, and gastric contents 6 mg. Screening for volatiles, drugs of abuse, alkaline compounds, and acid/neutral compounds was negative with the exception of ibuprofen (<2 mg/L) detected in peripheral blood. This report presents a fatality that appears to be associated with an isolated and acute GBP ingestion.

Drug abuse monitoring: which pharmacoepidemiological resources at the European level?

Monitoring the potential for abuse and dependence of psychoactive substances falls within the scope of international conventions on narcotic drugs. At the European level, this monitoring is based on activities controlled by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) for substance abuse in general and by the European Medicines Agency (EMA) for marketed drugs, in the context of pharmacovigilance. If France has set up in the early 1990s an original system to assess potential for abuse of psychoactive substances, with specific tools combining both the evaluation of the use of these substances (illicit substances or diverted drugs), and the consequences of that use in terms of morbidity and mortality, there is no equivalent in other European countries. Indeed, unlike the USA, who, for several decades, organized this type of surveillance, with a multisource approach (sentinel systems, databases, medical and administrative data, databases for seeking care in relation abuse), we have not found in other European countries integrated system for identifying a signal of drug abuse, or to assess the impact of measures for minimizing the risk of abuse. However, some recent examples show a growing concern about drug addiction, based on a pharmacoepidemiological approach using pharmacovigilance databases or medical administrative data. These examples illustrate the interest of these approaches in the field of drug of abuse.

Prescription opioid abuse based on representative postmortem toxicology

Opioids are important medications for pain and opioid maintenance treatment. Increasing use and abuse of prescription opioids has, however, caused worldwide concern. Our aim was to estimate the ratio between prescription opioid abuse and total use, based on representative postmortem toxicology. Our material included all the medico-legally examined deaths in Finland during 2010-2011 involving positive findings involving buprenorphine, codeine, fentanyl, methadone, oxycodone, or tramadol. We studied drug abuse by age group, with "abuse" meaning licit opioids used illicitly as narcotics. Drug-abuse history, drug injecting, or laboratory findings of illicit drugs defined an abuser case. We then compared abuser cases and other opioid-related cases between the opioids with the number of fatal poisonings, accidents, suicides, alcohol findings, concomitant opioid use, and median postmortem blood opioid concentrations. Opioid findings numbered 2499 in 2088 cases. Drug abuse involved 545 opioid-positive cases, which in Finland represented 0.5% of those deceased. The proportion of abuser cases among all opioid-related cases for buprenorphine was 85.5%, for methadone 82.4%, for tramadol 29.4%, for codeine 16.3%, for fentanyl 14.5%, and for oxycodone 6.9%. Abuse in age-groups >60 was rare. Concomitant other opioid findings were more frequent in abuser- than in other cases for codeine, oxycodone, and tramadol, whereas alcohol findings were more frequent in buprenorphine, codeine, and fentanyl abuse. Buprenorphine and methadone were most often related to drug abuse. Every other opioid studied involved some abuse, and especially tramadol. Abuse and fatal poisonings were concentrated in men aged 20-49.

Pregabalin serum levels in apprehended drivers

Pregabalin is a medicinal drug used mainly for the treatment of epilepsy and neuropathic pain. It has been shown to possess an abuse potential and in recent years some reports of illegal use have been published. In order to further evaluate the extent and nature of pregabalin abuse, serum pregabalin levels of drivers apprehended for driving under the influence of drugs (DUID) in Finland in 2012 were assessed. The samples were analysed by an LC-MS/MS system and the results were evaluated in relation to the typical therapeutic range of pregabalin as well as the age and gender of the driver. Pregabalin was detected in 206 samples in the study period. The median (range) serum concentration was 6.2 (0.68-111.6)mg/L. In nearly 50% of the cases the serum concentration was above the typical therapeutic range. In most of the cases the driver had also taken other drugs besides pregabalin, the mean number of concomitantly taken drugs being four. Our data indicate that pregabalin is being used at high doses, probably for recreational purposes. The vast majority of the drivers positive for pregabalin in our study material had used pregabalin as a part of a spectrum of psycho-active drugs and thus qualified as probable drug abusers. In these cases pregabalin probably contributed to their driving impairment but to what extent remained unclear in this study.