Profiles of pregabalin and gabapentin abuse by postmortem toxicology

Review of the demographic factors and toxicology related to deaths due to pregabalin in Northern Ireland

The potential for recreational abuse of the analgesic and antiepileptic drug pregabalin is now well established in the literature. The potential minimum lethal dose in post mortem cases is however less defined. All post mortem examinations in Northern Ireland where the cause of death was found to be due to pregabalin were examined for demographic and toxicological analysis. Deaths are generally seen in young men, especially 30-39-year-olds, many of whom have a history of substance misuse and are often prescribed pregabalin. Until recently, prescription rates have been on the rise regionally. The overall median post mortem peripheral blood concentration of pregabalin found in this study is 10.6 mg/L, however this rises when concurrent drugs and alcohol are considered and in cases where pregabalin is considered responsible for death alone (i.e. outside of multidrug toxicity). Pregabalin peripheral blood concentrations returned in this study suggest previously offered minimum lethal dosages may need to be revised downward.

Gabapentinoids in Ireland 2010 to 2020: An observational study of trends in gabapentinoid prescribing, law enforcement drug seizures and postmortem toxicology

AIMS

We explored trends in gabapentinoid prescribing, drug seizures and postmortem toxicology using a national pharmacy claims database, law enforcement drug seizures data and a population-based postmortem toxicology database.

METHODS

Gabapentinoid prescribing rates per 100 000 eligible population (2010-2020), annual number of drug seizures involving gabapentinoids (2012-2020) and gabapentinoid detection (positive) rates per 100 postmortem toxicology case (2013-2020) were calculated. Negative binomial regression models were used to evaluate longitudinal trends for gabapentin and pregabalin separately.

RESULTS

Gabapentin (adjusted rate ratio [RR] 1.06, 95% confidence interval [CI] 1.05-1.06, P < .001) and pregabalin (adjusted RR 1.08, 95% CI 1.08-1.09, P < .001) prescribing increased annually, with higher rates of pregabalin (vs. gabapentin) observed every year. Drug seizures involving pregabalin also increased over time (RR 1.54 95% CI 1.25-1.90, P < .0001). Of the 26 317 postmortem toxicology cases, 0.92% tested positive for gabapentin, and 6.37% for pregabalin. Detection rates increased for both gabapentin (RR 1.28, 95% CI 1.11-1.48, P < .001) and pregabalin (RR 1.13, 95% CI 1.11-1.48, P < .001) between 2013 and 2020. A total of 1901 cases (7.2%) tested positive for heroin/methadone; this sub-group had a higher detection rate for pregabalin (n = 528, 27.8%) and gabapentin (n = 41, 2.2%) over the study period, with a high burden of codetections for pregabalin with benzodiazepines (peaking at 37.3% in 2018), and pregabalin with prescription opioids (peaking at 28.9% in 2020).

CONCLUSION

This study raises concerns regarding the wide availability of pregabalin in Ireland, including a growing illicit supply, and the potential for serious harm arising from poly drug use involving pregabalin among people who use heroin or methadone.

Development of diabetic macular oedema shows associations with systemic medication - An epidemiological study

PURPOSE

To identify associations between systemic drugs and the incidence of diabetic macular oedema (DME). Of interest was to find beneficial and/or deleterious associations of used drugs.

METHODS

A historic cohort design based on administrative data. Study population consisted of 150 353 individuals with diabetes. Endpoint event was the development of DME (ICD-10 H36.01), censoring events were death or study end December 2017. The follow-up started between 1997 and 2010. The systemic medication consisted of 95 substances. We constructed a nested case-control study design comparing 2630 cases with DME to 13 144 age- and sex-matched controls without DME. Results are reported as odds ratios (ORs) with 95% confidence intervals (CIs) based on conditional logistic regression models.

RESULTS

Incidence rate for DME was 1.80 per 1000 person-years (95% CI 1.73-1.87). In all, we observed a lower incidence rate of DME in females (IRR 0.57; 95% CI 0.52-0.62) compared to males. Exposure to hormone replacement therapy estradiol (OR 0.42; 0.25-0.68), temazepam (0.23; 0.08-0.62) and allopurinol (0.61; 0.43-0.86) were associated with lower risk of DME, while use of insulin or insulin analogue (3.30; 2.99-3.64), sulfonylureas (1.21; 1.05-1.40), diuretic furosemide (1.90; 1.61-2.24), calcium channel blocker amlodipine (1.53; 1.34-1.75), ACE inhibitors ramipril (1.66; 1.46-1.89) and enalapril (1.38; 1.16-1.64) were associated with an increased risk of DME.

CONCLUSIONS

Large-scale studies examining the incidence of DME are lacking. Our findings suggest that associations of systemic medications with the incidence of DME may shed light on the pathogenesis of complex DME, encouraging further studies.

Prescription analgesic medication use among osteoarthritis patients

OBJECTIVE

Pharmacotherapy is the most common strategies to reduce pain for osteoarthritis (OA) patients. To analyze the trend and pattern of prescription analgesic medication use in American OA patients. Besides, our study also tried to figure out the demographic characteristics of opioid use among OA population which may helpful for managing the use of opioids.

METHODS

We included 2214 OA patients from 2007 to 2018. We extracted data from National Health and Nutrition Examination Survey (NHANES) database. We compared analgesics and anti-depression medications use by category between survey participants with OA and without.

RESULTS

For OA patients, NSAIDs, acetaminophen and gabapentinoid were the mostly highly used analgesics (10.2%, 9.0% and 8.9%, respectively). However, we also found that opioids use was very common in OA patients (7.7%) and the duration of opioids use was significantly long. In addition, the opioids use did not decrease from 2007 to 2018, while gabapentinoid increased rapidly from recent decade (From 5.0% to 12.1%). The common analgesic combination used by OA population was opioids with acetaminophen and gabapentinoid with selective serotonin reuptake inhibitors (SSRIs) (2.9% and 2.7%, respectively).

CONCLUSION

The use of gabapentinoid increased rapidly from recent decade, while opioids use did not decrease. The long-term excessive use of opioids was also a serious problem for OA pain control. More improvements such as focusing more on healthcare education and paying more attention on non-pharmacotherapy and the psychological situation of patients are needed.

Gabapentinoid detection in coronial casework in Gold Coast, Australia: a 5-year retrospective study

Gabapentinoids is a class of drug with analgesic, anxiolytic, and anticonvulsant properties and has a reported increase in prescription, use, and adverse outcomes. Regional studies are scant, and postmortem toxicological data may characterise patterns of regional use and inform local interventions. Characterising drug and non-drug-related deaths with gabapentinoid detection may also aid in toxicology interpretation. A 5-year retrospective study on all deaths admitted to the Gold Coast University Hospital under where toxicological analysis was performed. Of the gabapentinoids, only pregabalin was detected over the study period, and annual rates of detection did not differ significantly over the period (7.4-12.4%). In cases where pregabalin was detected, it was 15 times more likely to be a drug-related death. Drug-related deaths where pregabalin was detected have higher levels of pregabalin, are younger, and had a greater proportion of concurrent opioid detection. Postmortem detection of pregabalin was associated with drug-related deaths. Higher levels, younger decedents, and concurrent use of opioids were found in drug-related deaths. Public health interventions and regulated prescribing to target concurrent pregabalin and opioid use may address the burden of pregabalin drug-related deaths.

Drug prescriptions preceding opioid-related deaths-a register study in forensic autopsy patients

BACKGROUND/AIM

Opioid overdose deaths have increased in Sweden and other developed countries in recent decades, despite increased treatment efforts and harm-reduction interventions. Further knowledge in this field is needed if this trend is to be reversed. Previous research suggests that mental health and patterns of prescription of opioids and other prescription drugs are associated with increased opioid-related mortality. The present study therefore aimed to investigate what drugs were prescribed during the last six months of life to individuals with a history of illicit substance use who died with opioids present in their blood, the relationship between drugs prescribed and drugs found in blood at time of death, and if prescription of specific drugs was temporally associated with death.

METHODS

This was a retrospective, register-based observational study that utilized data from the National Board of Forensic Medicine, the Prescribed Drug Registry, regional health care services, and municipal social services. We used conditional logistic regression to find temporal associations between the prescription and dispensing of drugs and time of death.

RESULTS

Prescription and dispensing of alprazolam and diazepam were temporally associated with death. The most frequently dispensed drugs were zopiclone, pregabalin, methylphenidate, diazepam and oxycodone. Methadone, alprazolam, and buprenorphine were the drugs most often found in the blood. Opioids and tranquilizers in combination were found in a vast majority of deaths, and prescription data suggested that the use of these drugs was illicit in a majority of cases.

CONCLUSION

Prescription of certain drugs, especially alprazolam and diazepam, should be made with great caution to patients with a history of illicit substance use or concurrent use of opioids.

Effects of Gabapentinoids on Heroin-Induced Ventilatory Depression and Reversal by Naloxone

Despite an increasing prevalence of gabapentinoids (gabapentin and pregabalin) in opioid overdose deaths, little research has evaluated potentially harmful interactions between gabapentinoids and opioids. This study sought to determine the effects of gabapentinoids on the ventilatory depressive effects of heroin and their reversal by naloxone. Rats were given gabapentin, pregabalin, or saline prior to receiving increasing doses of heroin while ventilation was monitored using whole-body plethysmography. In some sessions naloxone was administered following the largest dose of heroin. The primary outcomes of this study were minute volume and Pause. Heroin dose-dependently reduced minute volume and increased Pause. Administration of naloxone dose-dependently reversed the effects of heroin on ventilation. Gabapentinoids did not alter the ventilatory depressive effects of heroin alone but reduced the potency of naloxone to reverse heroin-induced ventilatory depression. These preliminary findings emphasize the need for further research evaluating interactions between gabapentinoids and opioids related to substance misuse and overdose.

Trends in gabapentinoid prescribing in UK primary care using the Clinical Practice Research Datalink: an observational study

Background

The UK government reclassified gabapentin and pregabalin as 'controlled drugs' from April 2019. This study aimed to describe the trends in gabapentinoid prescribing before and immediately after reclassification, in the UK Clinical Practice Research Datalink, an electronic primary care health record broadly representative of the UK.

Methods

Separately for gabapentin and pregabalin, we calculated annual incident and prevalent prescribing rates from year of UK approval (April 1997 and 2004 respectively) to September 2019, and monthly incident and prevalent prescribing rates (October 2017-September 2019). Significant changes in temporal trends were determined using joinpoint regression. We also described potential prescribing indications, prior pain-related prescribing, and co-prescribing with potentially interacting medicines.

Findings

Incident gabapentin prescribing increased annually, peaking in 2016-17, at 625/100,000 patient years before falling steadily to 2019. Incident pregabalin prescribing peaked at 329/100,000 patient years in 2017-18 and did not fall significantly until 2019. Prevalent gabapentin and pregabalin prescribing increased annually to 2017-18 and 2018-19 respectively, before plateauing. Gabapentinoids were commonly co-prescribed with opioids (60%), antidepressants (52%), benzodiazepines (19%), and Z-drugs (10%).

Interpretation

Following a dramatic rise, incident gabapentinoid prescribing has started to fall but the specific impact of reclassification on prescribing rates remains unclear. Limited change in prevalent gabapentinoid prescribing during the 6 months following their reclassification as controlled drugs suggests little immediate impact on continued gabapentinoid prescribing for existing users.

Funding

National Institute for Health and Care Research (NIHR) Research for Patient Benefit Programme. NIHR Applied Research Collaboration West Midlands. NIHR School for Primary Care Research.

Risk of major adverse events associated with gabapentinoid and opioid combination therapy: A systematic review and meta-analysis

Background: The use of opioid-gabapentinoid combinations has increased, raising several safety concerns. However, meta-analysis studies focusing on this issue are limited. Objective: To evaluate the risk of central nervous system (CNS) depression, gastrointestinal (GI) adverse events, and mortality of combination therapy compared with those of opioid therapy and to explore the differences in the results according to study design and indications. Methods: Relevant studies were selected (published before 30 January 2022) by searching the MEDLINE, Embase, and CENTRAL databases. The pooled odds ratios (OR) with 95% confidence intervals (CI) of the outcomes were estimated using the Mantel-Haenszel method. Subgroup and meta-regression analyses were performed according to study characteristics. Quality assessment was conducted using the Risk of Bias 2 tool for randomized controlled trials (RCTs) and Cochrane Collaboration's Risk of Bias in non-RCTs tool for non-randomized trials. Results: Adverse events were reported in 26 RCTs and 7 non-RCTs, and mortality was reported in 10 non-RCTs. Compared to opioid therapy, dizziness, cognitive dysfunction, and respiratory depression in combination therapy significantly increased in non-RCTs (OR 3.26, 95% CI 1.82-5.85; OR 3.13, 95% CI 1.51-6.50; OR 1.71, 95% CI 1.31-2.24, respectively), and a similar trend for dizziness and cognitive dysfunction was also identified in the RCT analysis, although the difference was not significant. Combination therapy for cancer pain was associated with the highest risk of sedation in subgroup analysis. Combination therapy significantly decreased the risk of GI adverse events, including nausea, vomiting, and constipation. The mortality risk associated with combination therapy was higher than that associated with opioid therapy (OR 2.76, 95% CI 1.26-6.05). Conclusion: Opioid-gabapentinoid combination therapy could be associated with an increased risk of CNS depression and mortality, despite tolerable GI adverse events. These data suggest that combination therapy requires close monitoring of CNS depression, especially in cancer patients. Caution is needed in interpreting the clinical meanings owing to the lack of risk difference in respiratory depression in the RCT-only analysis and the absence of RCT or prospective studies investigating mortality.

Adverse outcomes associated with concurrent gabapentin, opioid, and benzodiazepine utilization: A nested case-control study

Background

Gabapentin, opioids, and/or benzodiazepines are commonly prescribed for a variety of pain and psychiatric conditions. Despite the high likelihood of co-prescription of these medications, little is known about co-utilization of gabapentin (GABA), opioids (OP), and benzodiazepines (BZD) and associated public health outcomes.

Methods

Using Medicare CCW Data, 2013-2016, we conducted a nested case-control study to examine the association between concurrent utilization of GABA, OP, and BZD and respiratory depression, opioid, and substance-related overdose among Medicare disabled beneficiaries. Cases and controls were Fee-for-service disabled beneficiaries who had a diagnosis of acute pain (AP), chronic pain (CP) or mental health conditions (MH) and received GABA, OP or BZD. Cases with respiratory depression, opioid or substance-related overdose were matched with up to 4 controls on socio-demographics, year of cohort entry and disease risk score. Primary exposure was concurrent medication utilization defined as an overlap of at least one day in prescriptions for GABA, OP and BZD.

Findings

Across all cohorts, the majority of cases and controls were under 65, female, dually eligible and had prior histories of pain and mental health conditions. GABA+OP+BZD use was associated with increased odds of respiratory depression [AOR(95%CI)-AP: 1.35 (1.19-1.52), CP:1.24 (1.11-1.38) and MH: 1.16 (1.02-1.32) vs. OP only], opioid-related overdose [AP: 1.43 (1.04-1.98), CP: 1.47 (1.07-2.00) and MH: 1.44 (1.04-2.00) vs. OP only], and substance-related overdose [AP: 1.77 (1.26-2.50), CP: 1.70 (1.24-2.34) and MH: 1.92 (1.31-2.82) vs. GABA only]. While there were cohort differences in the association between GABA+OP and both respiratory depression and opioid-related overdose, GABA+OP and GABA+BZD use were associated with significantly higher odds of substance-related overdose across all clinical cohorts.

Interpretation

Among Medicare disabled beneficiaries, concurrent utilization of gabapentin, opioids, and benzodiazepines is associated with multiple adverse outcomes. Given this, it is imperative that the benefits and risks of co-prescribing these medications be comprehensively examined.

Funding

None.

Fatalities associated with gabapentinoids in England (2004-2020)

The gabapentinoids were reclassified as Schedule II medications and Class C drugs in the UK in 2019 due to their potential misuse. In this study we examined deaths following gabapentinoid use in England reported to the National Programme on Substance Abuse Deaths.

A total of 3051 deaths were reported (gabapentin: 913 cases; pregabalin: 2322 cases [both detected in 184 cases]). Prescribed and illicitly obtained gabapentinoids accounted for similar proportions of deaths (gabapentin illicit 38.0%, prescribed 37.1%; pregabalin illicit 41.0%, prescribed 34.6%). Opioids were co‐detected in most cases (92.0%), and co‐prescribed in a quarter (25.3%). Postmortem blood gabapentinoid concentrations were commonly (sub)therapeutic (65.0% of gabapentin cases; 50.8% of pregabalin cases). In only two cases was gabapentinoid toxicity alone attributed in causing death.

Gabapentinoids alone rarely cause death. Clinically relevant doses can, however, prove fatal, possibly by reducing tolerance to opioids. Doctors and patients should be aware of this interaction.

Gabapentinoid–opioid co‐prescribing needs urgent revision.

Role of Acetaldehyde in Ethanol Reversal of Tolerance to Morphine-Induced Respiratory Depression in Mice

Background: Opioid users regularly consume other drugs such as alcohol (ethanol). Acute administration of ethanol rapidly reverses tolerance to morphine-induced respiratory depression. However, recent research has suggested that the primary metabolite of ethanol, acetaldehyde, may play a key role in mediating the CNS effects seen after ethanol consumption. This research investigated the role of acetaldehyde in ethanol reversal of tolerance to morphine-induced respiratory depression.

Methods: Tolerance was induced in mice by 6-days implantation of a 75 mg morphine pellet with control mice implanted with a placebo pellet. Tolerance was assessed by acute morphine administration on day 6 and respiration measured by plethysmography. Levels of acetaldehyde were inhibited or enhanced by pre-treatments with the acetaldehyde chelator D-penicillamine and the inhibitor of acetaldehyde dehydrogenase disulfiram respectively.

Results: Morphine pellet implanted mice displayed tolerance to an acute dose of morphine compared to placebo pellet implanted controls. Acute acetaldehyde administration dose-dependently reversed tolerance to morphine respiratory depression. As previously demonstrated, ethanol reversed morphine tolerance, and this was inhibited by D-penicillamine pre-treatment. An acute, low dose of ethanol that did not significantly reverse morphine tolerance was able to do so following disulfiram pre-treatment.

Conclusion: These data suggest that acetaldehyde, the primary metabolite of ethanol, is responsible for the reversal of morphine tolerance observed following ethanol administration.

Patterns of opioid and benzodiazepine use with gabapentin among disabled Medicare beneficiaries - A retrospective cohort study

BACKGROUND

Our goal was to describe specific patterns associated with co-prescriptions of gabapentin, opioids, and benzodiazepines among disabled Medicare beneficiaries.

METHODS

Using 2013-2015 Medicare data, we conducted a retrospective cohort study among fee-for-service disabled beneficiaries continuously enrolled in Medicare Parts A, B, and D. The index date was defined as the earliest fill date for a gabapentin, opioid, or benzodiazepine prescription. Monotherapy, dual therapy, and tri-therapy were defined as utilization of one, two, and three medication classes, respectively. Augmentation was defined as a prescription for a different medication class in addition to prescription for initial medication; switching referred to a change in prescription for a different medication class with no subsequent fills of initial medication. We used descriptive statistics, Kaplan Meier analyses and Cox proportional hazards to examine the association between initial therapy and monotherapy, dual therapy, tri-therapy, switching and augmentation.

RESULTS

Among 151,552 disabled beneficiaries, gabapentin initiators were more likely to augment therapy (50.1%) when compared to opioid (28.7%) and benzodiazepine (38.7%) users. When compared to opioid initiators, the risk of augmentation (HR[95%CI]: 1.85[1.82-1.89]) and switching (1.62 [1.51-1.73]) was significantly higher among gabapentin initiators. Risk of augmentation was also significantly higher among beneficiaries with co-morbid pain and mental health conditions (p < 0.01). Overall, the majority of beneficiaries augmented and switched within 2-months and 4-months after initiating therapy, respectively.

CONCLUSIONS

Given safety concerns associated with gabapentin, opioids, and benzodiazepines, it is imperative that the benefits and risks of co-prescribing these medications be examined comprehensively, especially for those in vulnerable sub-groups.

Managing the misuse potential and risk of psychological harm from gabapentinoids in primary care in New Zealand

Gabapentinoid prescribing is increasing in New Zealand. International evidence suggests that this prescribing trend is followed by increasing harms, including misuse, dependence, overdose, and psychological harms including suicidal thoughts or behaviours. However, there is limited guidance for prescribers on how to manage these potential harms. Here, we summarise the current international literature and identify three main risk factors that can be used for screening purposes when considering prescribing a gabapentinoid, to identify patients that may be at greater risk of harm. Based on current knowledge of harms, we provide guidance to prescribers on monitoring patients taking gabapentinoids. Finally, we summarise the evidence regarding tapering, and highlight key knowledge gaps including other interventions, referral, and data from primary care populations.

Extracorporeal Treatment for Gabapentin and Pregabalin Poisoning: Systematic Review and Recommendations From the EXTRIP Workgroup

Toxicity from gabapentin and pregabalin overdose is commonly encountered. Treatment is supportive, and the use of extracorporeal treatments (ECTRs) is controversial. The EXTRIP workgroup conducted systematic reviews of the literature and summarized findings following published methods. Thirty-three articles (30 patient reports and 3 pharmacokinetic studies) met the inclusion criteria. High gabapentinoid extracorporeal clearance (>150mL/min) and short elimination half-life (<5 hours) were reported with hemodialysis. The workgroup assessed gabapentin and pregabalin as "dialyzable" for patients with decreased kidney function (quality of the evidence grade as A and B, respectively). Limited clinical data were available (24 patients with gabapentin toxicity and 7 with pregabalin toxicity received ECTR). Severe toxicity, mortality, and sequelae were rare in cases receiving ECTR and in historical controls receiving standard care alone. No clear clinical benefit from ECTR could be identified although major knowledge gaps were acknowledged, as well as costs and harms of ECTR. The EXTRIP workgroup suggests against performing ECTR in addition to standard care rather than standard care alone (weak recommendation, very low quality of evidence) for gabapentinoid poisoning in patients with normal kidney function. If decreased kidney function and coma requiring mechanical ventilation are present, the workgroup suggests performing ECTR in addition to standard care (weak recommendation, very low quality of evidence).

Gabapentinoids: The rise of a new misuse epidemics?

Gabapentinoids and opioids have in common that they are used in medicine in the treatment of pain, and by addicts in recreational use. In recent years, in the context of the "opioid epidemics", gabapentinoids, which had a reputation for low risk of abuse, have been increasingly prescribed. This was accompanied by increasingly frequent abuses, the patients most at risk being those suffering from opiate addiction. However, gabapentinoids increase the risks associated with opioids or other sedatives, due to a synergy of central depressant effects. This leads to reconsider the framework of their prescription and the management of chronic pain.

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.

Characteristics of fatal gabapentinoid-related poisoning in Australia, 2000-2020

INTRODUCTION

Gabapentinoids are centrally active GABA agonists whose use has increased substantially in the past decade. The current study aimed to provide a comprehensive clinical profile of a national case series of fatal poisonings related to gabapentinoids.

METHODS

Retrospective study of all deaths due to drug toxicity in Australia in which gabapentinoids were a contributory mechanism, retrieved from the National Coronial Information System (2000-2020). Information was collected on case characteristics, toxicology and major organ pathology.

RESULTS

A total of 887 cases were identified, with a mean age of 45.7 years and 55.2% being male. Death was due to accidental toxicity in 81.3% of cases and intentional in 18.7%. Pre-existing disease was co-contributory to drug toxicity in 19.5%. Pregabalin was present in 92.9% of cases, with a median blood concentration of 7.6 mg/L (range 0.1-850.0 mg/L). Gabapentin was present in 7.2%, with a median blood concentration of 9.5 mg/L (range 0.5-1940.0 mg/L). Both pregabalin and gabapentin were present in five cases. No other gabapentinoids were detected. Drugs other than gabapentinoids were present in 99.8%, most frequently opioids (90.1%), hypnosedatives (76.9%) and antidepressants (60.5%). A body mass index in the obese range was seen in 45.4%. Clinically significant pre-existing disease was common, notably cardiomegaly (24.9%), emphysema (20.2%), nephrosclerosis (18.7%) and severe hepatic steatosis (11.7%).

CONCLUSIONS

The concomitant use of other drugs was close to universal, with CNS depressants predominating. Mental health problems, chronic pain and substance misuse were prominent.

Toxicological Relevance of Pregabalin in Heroin Users: A Two-Year Post-Mortem Population Study

Pregabalin (PGL) is a gabapentinoid used to treat epilepsy, neuropathic pain and generalized anxiety disorder. PGL is also misused by heroin users as it enhances the effects of heroin. While it is thought those who misuse PGL take it in amounts greater than the recommended therapeutic dose, it is unknown whether there is a significant difference between the amounts of PGL used by heroin users compared to non-heroin users. This study hypothesised that the PGL concentrations in post-mortem samples taken from heroin users positive for PGL would be higher than those in non-heroin users. Between 01.01.2016 and 31.12.2017, a routine drugs screen and a specific screen for PGL was carried out on femoral-vein bloods from 3,750 post-mortem Coroners' cases. Of the cases screened, 354 were heroin users, of which 264 cases were negative for gabapentinoids and therefore used as the control-heroin users group. PGL was positive in 229 cases, of which 69 were heroin users and 160 were non-heroin users. On comparing the PGL concentrations, statistically higher concentrations were observed in the heroin users compared to non-heroin users (P = 0.002). There was no correlation between the concentrations of PGL and morphine (from heroin) in the heroin users (P = 0.95), and the amount of heroin (morphine) consumed was not dependant on whether PGL was consumed or not (P = 0.98). The prevalence of anti-depressants, benzodiazepines, methadone and non-heroin related opioids were seen to be significantly higher in heroin users that were positive for PGL than the control-heroin users (P = < 0.001 for all drugs). This study suggests that heroin users are using greater amounts of PGL compared to non-heroin users; however, the magnitude of the difference in use may not be sufficient to conclude that heroin users are at substantially greater risk of pregabalin toxicity compared to non-heroin users. Results indicate that heroin users who take PGL are more likely to use multiple depressant drugs, hence increasing the risk of multi-drug toxicity and death in this population.

Pregabalin and gabapentin in non-opioid poisoning deaths

Post-mortem findings of gabapentinoids have often been connected to drug abuse and especially opioid use. We aimed to investigate whether gabapentinoids have been implicated in the cause of death without the presence of opioids. In a three-year study period from 2016 to 2018, a total of 907 Finnish post-mortem cases positive for pregabalin or gabapentin were found. In nearly half of the pregabalin cases and in a third of the gabapentin cases, the blood concentration was above the typical therapeutic range of the drug. Of the cases in which pregabalin was detected, in 35% the drug was implicated in a fatal poisoning with or without other drugs or alcohol. For gabapentin, the percentage was 22%. In most of the fatal gabapentinoid poisonings, opioids or other central nervous system depressants were additionally detected in relevant concentrations. There were eight non-opioid gabapentinoid poisonings, in which no relevant other drugs were detected. Many of these cases were unintentional poisonings with a relatively high gabapentinoid concentration in the blood. In all but one, the manner of death was accidental, or the intent was undetermined. This study confirmed the previous findings that gabapentinoids are mostly implicated in fatal poisoning together with opioids. Half of the non-opioid cases were related to drug abuse but in the other half the death was presumably caused by overuse of a prescribed drug or suicide. While the use of gabapentinoids is a well-known problem among people who use drugs, it is important to note other groups of users who may be at risk of overdose by gabapentinoids.

[Pregabalin abuse and dependence in various European countries: Association with substitution policies]

INTRODUCTION

Pregabalin was first approved in 2004 for the treatment of peripheral neuropathic pain and focal epileptic seizures, with or without secondary generalization. Prescription frequency has increased significantly since approval. In the early days, little attention was paid to the problem of misuse and dependence on pregabalin; in recent years, there has been a significant increase in the number of publications focusing on this problem. This review deals with these risk factors and risk groups of pregabalin abuse and dependence in different European countries and their drug policies.

RESULTS

Pregabalin abuse and dependence has increased significantly since its introduction to the market. It was shown that solo abuse of pregabalin is rare. In most cases, pregabalin was combined with other substances, which is also a predictor of pregabalin abuse. There were different reasons for the non-prescription use of pregabalin; it was used to increase the psychotropic effect, on the one hand, and to alleviate withdrawal symptoms, on the other hand. Furthermore, in Sweden, pregabalin was found in 28% of fatal intoxications among drug addicts. Young people were particularly affected. Abuse of pregabalin was detected in countries with restrictive substitution programmes, while in countries with liberal drug policies, no abuse was detected. However, the data situation in Switzerland with a liberal substitution programme is based on only one study, which is why pregabalin use in liberal substitution programmes cannot be conclusively clarified.

CONCLUSIONS

There seems to be a connection between a country's drug policy and the illegal use of pregabalin among persons in a substitution programme in that country. There are also risk factors and risk groups for pregabalin dependence and abuse.

Gabapentinoid misuse, abuse and non-prescribed obtainment in a United States general population sample

Background Reports of gabapentinoid (gabapentin and pregabalin) misuse are on the rise, but few studies have assessed this within the general US population. Objective Describe lifetime misuse/abuse/non-prescribed obtainment of gabapentinoids and descriptive characteristics associated with such actions in a US general population sample. Setting This cross-sectional questionnaire was administered online by Qualtrics^® research panel aggregator via quota-based sampling. Methods Data were collected from a sample of respondents that mirrored the general US population aged 18-59 years with regards to age, geographic region, ethnicity, income, and education level, based on most recent census data. Misuse/abuse/non-prescribed obtainment was collectively defined as use of a gabapentinoid for reasons other than a diagnosed medical condition, using with the intention of altering one's state of consciousness, or obtaining without a prescription. A multivariable logistic regression model was created to predict misuse/abuse/non-prescribed obtainment of gabapentinoids, incorporating relevant covariates. Main outcome measure Proportion of sample indicating lifetime misuse/abuse/non-prescribed obtainment of gabapentinoids. Results Among 1,843 respondents, 121 (6.6%) reported gabapentinoid misuse/abuse/non-prescribed obtainment. Specifically, 2.1% (n = 39) and 1.5% (n = 27) of respondents for gabapentin and pregabalin, respectively, met study criteria for abuse. Opioids were the most common medication co-administered with gabapentinoids (among 50-70% of respondents) for misuse/abuse. Previous treatment for addiction (OR: 2.61, 95% CI: 1.32-5.14, p = 0.005) and the total attitudinal risk score (OR: 1.14, 95% CI: 1.09-1.19, p < 0.001) were associated with gabapentinoid misuse/abuse/non-prescribed obtainment. Conclusion Among those surveyed, 6.6% reported previous gabapentinoid misuse/abuse/non-prescribed obtainment, providing one of the first estimates within a nationally distributed, US general population sample.

Gabapentinoid Abuse in France: Evidence on Health Consequences and New Points of Vigilance

Introduction: Gabapentinoid drugs (gabapentin and pregabalin) are widely used worldwide for epileptic and pain disorders. First signals of gabapentinoid abuse occurred in the last decade. This study aims to describe clinical characteristics of gabapentinoid use related disorders and health consequences in France. Materials and Methods: We designed a multisource investigation reviewing data reported to the French Addictovigilance Network (FAN) with pregabalin and gabapentin from 2010 to 2019. Information was obtained through the analysis of Spontaneous Reports (SRs) notified by health professionals and the pharmacoepidemiological surveys OSIAP (suspicious prescriptions forms indicators of potential abuse), OPPIDUM (observation of illicit drugs and misuse of psychotropic medications), DRAMES (death related to prescription drugs and other substances), and DTA (toxic deaths due to analgesics). Results: Over 2010-2019 period, were collected: (i) 265 SRs (258 pregabalin; 7 gabapentin); (ii) 816 forged prescription forms (805 pregabalin, 10 gabapentin, 1 involving both drugs); (iii) 145 cases of gabapentinoid use in people who use drugs (121 pregabalin; 24 gabapentin) and (iv) 31 cases of gabapentinoid-related deaths (25 pregabalin; 6 gabapentin). Risk factors of gabapentinoid abuse were opioid use disorders or psychiatric history, but cases of primary abuse in subjects without any substance abuse history were observed. Adverse outcomes concern almost exclusively pregabalin, with coma, dyspnea, convulsion, and conduction disorders. Treatment demands increased from 10.6% in 2018 to 23.1% in 2019, with pregabalin cited as the first substance leading to addictological care in the 2019 OPPIDUM survey. Gabapentinoid-related deaths increased over time. Pregabalin has become the first drug mentioned in forged prescriptions in 2019 (23.8% of OSIAP), while it ranked at the 15th position in 2017 (2.6%). Discussion: This study shows the importance of addictovigilance monitoring for gabapentinoids. Addictovigilance data helped to make visible the gabapentinoid-abuse related health harms (hospitalization for serious neurologic, psychiatric or cardiac effects, requests for addictological support and deaths) and to confirm the intrinsic abuse potential of pregabalin. These data highlight new points of vigilance considering observed primary abuse. At this point in France, the risk of abuse and related complications is very apparent with pregabalin. Still, it is identical to that observed elsewhere with 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.

Co-prescription of gabapentinoids and opioids among adults with and without osteoarthritis in the United Kingdom between 1995 and 2017

Objectives

To produce national and regional estimates and trends for gabapentinoid–opioid co-prescribing rates in patients with OA, both in absolute terms and relative to matched controls without OA.

Methods

Using the UK Clinical Practice Research Datalink database we first constructed age–sex–practice–date 1:1 matched cohorts of patients aged ≥40 years with and without a new diagnosis of OA between 1995–2017 and estimated the relative incidence of a first gabapentinoid prescription. Incident gabapentinoid users in both cohorts were followed to estimate and compare the event rate of gabapentinoid–opioid co-prescription (prescription from both classes within the same 28-day window).

Results

The incidence of first gabapentinoid prescription was 3-fold higher in patients with OA than in matched controls [n = 215 357; incidence rate ratio (IRR) 2.93; 95% CI: 2.87, 3.00]. Among incident gabapentinoid users with OA (n = 27 374, median follow-up 3.9 years) the event rate of gabapentinoid–opioid co-prescription was 4.03 (4.02–4.05) per person-year. The rate was higher in OA patients classed as long-term gabapentinoid users (6.24; 6.22–6.26). These rates were significantly higher than in incident gabapentinoid users without OA [adjusted-IRR: 1.29 (1.28–1.30)]. This elevated risk was observed across age, sex, geographic regions, and calendar years, when restricted to strong opioids and to long-term gabapentinoid users, and when co-prescription was defined as within 14 days and same-day prescribing.

Conclusions

Patients with OA not only have a higher risk of being prescribed a gabapentinoid but, once prescribed a gabapentinoid, are also at greater risk of opioid co-prescription. Strict restriction of gabapentinoid–opioid co-prescription, and improved access to, and uptake of, effective non-pharmacological and surgical alternatives for OA are required.

Gabapentin-induced drug-seeking-like behavior: a potential role for the dopaminergic system

Drugs of abuse represent a growing public health crisis. Accumulating evidence indicates that gabapentin (GBP), a prescription drug, is prone to misuse, abuse, withdrawal, and dependence. Commonly, drugs of abuse modulate the dopaminergic system to induce addiction. In this study, we used the conditioned place preference (CPP) model to investigate the involvement of the dopamine 1 (D1) receptor on the reward and reinforcement behavior of GBP. Under a CPP paradigm, male BALB/c mice were intraperitoneally injected either saline or 100, 200, or 300 mg/kg of GBP and confined to the injection-paired chamber for 30 min. In the pre-conditioning phase, mice were conditioned for 3 days, and baseline data were collected. In the conditioning phase, mice were given once-daily alternating injections of either GBP or saline for 8 days and subsequently assessed in a post-conditioning test. Injections of 300 mg/kg of GBP significantly increased the time spent in the drug-paired chamber compared to the saline-paired chamber. However, lower doses of GBP (100 and 200 mg/kg) showed no effect. Pre-treatment with SKF-83566, a D1 receptor antagonist, attenuated GBP-induced CPP. Thus, for the first time, we show that GBP can induce CPP through a dopaminergic-dependent mechanism.

Postmortem analysis of quetiapine and pregabalin in human bone

In this study quetiapine and pregabalin were analyzed in human bones. A method previously developed for the determination of antidepressants in human bone was tested for the analysis of these two substances. Bones were pulverized and subjected to the extraction protocol, and after undergoing solid-phase extraction, samples were analyzed using gas chromatography-mass spectrometry. The assay was validated in the range 0.3-500 ng/mg, mean analytical recovery was 76.9% for quetiapine and 90.9% for pregabalin, matrix effect was 83% for quetiapine and 91% for pregabalin and process efficiency was 63.8% for quetiapine and 82.7% for pregabalin. The intra- and inter-day precision was below 3% in all cases and the intra- and inter-assay accuracy values were in almost all cases better than 12%. The validated method was then applied to bone samples from forensic cases. Drugs were detected in bone in 2 of the 3 blood positive cases. The approximate concentrations in bone were 40 ng/mg for pregabalin and 7 ng/mg for quetiapine. To our knowledge, this is the first time these substances were detected in bones. With this study the number of substances with a validated protocol to be used in human bones in case of necessity is expanded.

Pregabalin and Its Involvement in Coronial Cases

Pregabalin is an anticonvulsant and analgesic designed to treat neuropathic pain and partial seizure disorders and has been available in Australia as a prescription medication since 2005. Studies have found high rates of polydrug use associated with pregabalin and it is reportedly used recreationally for its euphoric and relaxing effects as well as to self-manage opioid withdrawal symptoms. A robust analytical method for the analysis of pregabalin using protein precipitation and LC/MS/MS was developed, validated and employed in routine case work. In recent years a substantial increase in pregabalin detections in coronial case submissions had been noted. This study examines the case characteristics and outcomes of 332 coronial cases submitted to the laboratory and analyzed for pregabalin between 2015 and 2017. Pregabalin was identified in approximately 5% of all coronial cases submitted during this time. A high rate of concurrent drug use with pregabalin was evident with the predominant classes being opioids, benzodiazepines and anti-depressants. Post-mortem blood pregabalin concentrations ranged from <0.05 to 140 mg/kg (median 5.5 mg/kg); however, limited interpretation of levels could be achieved as the drug was rarely identified in the absence of other drugs. Cause of death (COD) was found to be drug related in 58% of all cases, with mixed drug toxicity specifically mentioned as related to COD in 40% of cases.

Pregabalin Abuse in Combination With Other Drugs: Monitoring Among Methadone Patients

INTRODUCTION

In recent years, there has been an increase in the non-medical use of psychoactive prescription drugs including pregabalin (PGB). Studies have shown that multiple drug users and patients in methadone treatment programs administered PGB at high dosages in order to achieve euphoria, reduce withdrawal symptoms, or potentiate the effects of methadone. For these reasons, accurate toxicological monitoring is required for these high-risk individuals.

MATERIALS AND METHODS

The present study investigated whether PGB could be detected in the hair samples of 250 patients with a history of opiate dependency, and under toxicological surveillance assess their compliance with methadone maintenance therapy.

RESULTS

Opiates were found in 54/250 of all hair samples, while cannabis was present in 74/250 patients, cocaine was detected in 21/250 patients, and benzodiazepines without prescription were identified in 49/250 patients. As expected, methadone was present in all 250 patients (100%). PGB without prescription was found in the hair samples of 35/250 patients (14%). Of these, 91.43% were male, 48.57% were <30 y old, and 45.71% were between ages 30 and 50 y. There were no apparent associations among PGB use, daily methadone dosage, and duration of methadone maintenance therapy. Psychiatric comorbidities were present in 25.71% of the patients abusing PGB. Anxiety (55.56%) and depression (33.33%) were the most prevalent psychiatric disorders.

DISCUSSION

Most of the patients taking PGB (57.14%) used other drugs (especially opiates) concurrently. The utility of hair analysis is explained by easy and rapid sample collection and the ability of the hair to reflect long-term drug use and incorporate drug metabolites. The findings of this study suggested that PGB has significant potential for abuse by high-risk populations such as opioid users and patients with dual diagnosis. These risks are particularly high in cases of poly-drug use and drug intake that are not in compliance with prescription guidelines.

A repeated cross-sectional study of factors associated with pregabalin-positive poisoning deaths in Ireland

BACKGROUND

The increasing use of pregabalin and the presence of pregabalin in poisoning deaths, particularly with opioids, highlight it as a potential drug of abuse. In this study we examined factors associated with pregabalin-positive poisoning deaths (PPPD) between 2013 and 2016 in Ireland.

METHODS

Data were extracted from the National Drug-Related Deaths Index (NDRDI). Analysis included univariate and multivariate logistic regression to estimate unadjusted and adjusted odds ratios (OR) and 95 % confidence intervals (CI) for factors associated with PPPD (primary outcome) by logistic regression models for the total sample and stratified by gender.

RESULTS

Pregabalin was present on 240 (16 %) toxicology reports of 1489 poisoning deaths; significantly rising from 15 (4.5 %) in 2013 to 94 (26 %) in 2016. Women (AOR 2.69, 95 % CI: 1.95-3.70), opioid misuse (AOR 1.74, 95 % CI: 1.17-2.59), in receipt of treatment for problem drug use (AOR 1.95, 95 % CI: 1.33-2.86) and year of death (2016 vs 2013) (AOR 7.95, 95 % CI: 4.58-13.79) were associated with increased odds of PPPD. Alcohol dependence was associated with reduced odds of PPPD (AOR 0.59, 95 % CI: 0.41-0.85). For men, opioid misuse, in receipt of treatment for problem drug use, and year of death were associated with increased odds of PPPD, while alcohol dependence was associated with reduced odds of PPPD. For women, in receipt of treatment for problem drug use and year of death were associated with increased odds of PPPD.

CONCLUSIONS

Enhanced training to prescribers and treatment providers on the potential risks associated with pregabalin, particularly among people who use drugs, is required.

Prescribed and non-prescribed gabapentin use among persons seeking inpatient opioid detoxification

BACKGROUND

Persons with opioid use disorder (OUD) are at increased risk for gabapentin misuse. Rising rates of concomitant gabapentin-opioid use in the U.S. are concerning given heightened risk of fatal overdose.

OBJECTIVE

To examine predictors of ever using gabapentin among persons seeking treatment for opioid use and to assess if reasons for gabapentin use differed by gender and how gabapentin was procured (prescribed, non-prescribed, or both).

METHOD

Persons with OUD were recruited from a managed withdrawal program. t-Tests and Pearson χ2 tests of independence were used to compare reasons for gabapentin use by gender and source of acquisition.

RESULTS

Among participants (n = 401; 69.1% male, 84.5% White, 86.8% sought treatment for heroin use, 90.0% insured), female gender, higher educational attainment, injection drug use (IDU), history of overdose, and chronic pain were associated with gabapentin use. Overall, reasons for use were similar across genders among those reporting a history of gabapentin use (65.8%), although males were more likely to use to get high than females. About half (47.0%) reported only using gabapentin that was not prescribed, 20.5% had only used prescribed gabapentin, and 32.5% reported prescribed and non-prescribed use. Persons prescribed gabapentin were most likely to use it to control pain (81.5%); for those using diverted gabapentin only and those reporting both prescribed and non-prescribed gabapentin use, the most common reasons for intake were to: get high, increase effects of heroin, substitute for opioids, and help with opioid withdrawal.

CONCLUSIONS

In this sample of people with OUD entering inpatient detoxification program, a majority reported a history of gabapentin use, with most using diverted gabapentin. The range of reasons for gabapentin use point to the need to better understand why co-use is common.

Validation of a High-throughput Screening and Quantification Method for the Determination of Gabapentinoids in Blood Using a Combination of LC-TOF-MS and LC-MS-MS

Gabapentinoids such as gabapentin (GP) and pregabalin (PGL) have been used to treat a wide range of neurological and psychiatric disorders. In recent years, there has been an increasing awareness of GP and PGL misuse among individuals with a history of polysubstance use. Both GP and PGL are understood to potentiate the effects of opioids, with fatalities involving GP and PGL being reported with increasing frequency. An efficient procedure was developed to screen and quantitate GP and PGL in blood samples using a combination of liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) and liquid chromatography tandem mass spectrometry (LC-MS-MS). The developed LC-MS-MS method was linear from 0.5-50 mg/L, with a limit of detection (LOD) of 0.1 mg/L for GP and PGL. An LOD of 0.5 mg/L was determined for both analytes on the LC-TOF-MS screen. A total of 1,091 blood specimens were subjected to a protein crash with methanol, in the presence of deuterated internal standards, PGL-d6 and GP-d10, to minimize the effects of varying matrix conditions. Specimens tested included both post-mortem blood and preserved blood specimens collected for the purposes of investigating drug-impaired driving and suspected drug-facilitated crimes. Of the total of specimens tested, 101 (9.3%) screened positive using the developed LC-TOF-MS method for GP while only 13 (1.2%) blood specimens screened positive for PGL. All (100%) of the cases that screened positive for GP and PGL were confirmed positive by LC-MS-MS. Blood concentrations of GP and PGL ranged from <0.5 to 215 mg/L and from <0.5 to 32 mg/L, respectively. Of the blood specimens that had previously screened negative by LC-TOF-MS, 10% (N = 100) were randomly selected and tested by LC-MS-MS with 100% confirmed negative for GP and PGL. The developed methods provide a fast and reliable high-throughput screening and confirmation testing strategy for the detection of GP and PGL in blood specimens.

Lack of correlation between the activity of the mesolimbic dopaminergic system and the rewarding properties of pregabalin in mouse

RATIONALE

Pregabalin is a psychoactive drug indicated in the treatment of epilepsy, neuropathic pain, and generalized anxiety disorders. Pregabalin acts on different neurotransmission systems by inactivating the alpha2-delta subunit of voltage-gated calcium channels. In light of this pharmacological property, the hypothesis has been raised that pregabalin may regulate the mesolimbic dopamine pathway and thereby display a potential for misuse or abuse as recently observed in humans. Although some preclinical data support this possibility, the rewarding properties of gabapentinoid are still a matter for debate.

OBJECTIVE

The aim of this work was to evaluate the rewarding properties of pregabalin and to determine its putative mechanism of action in healthy mice.

RESULTS

Pregabalin alone (60 mg/kg; s.c.) produced a rewarding effect in the conditioned place preference (CPP) test albeit to a lower extent than cocaine (30 mg/kg; s.c.). Interestingly, when assessing locomotor activity in the CPP, the PGB60 group, similarly to the cocaine group, showed an increased locomotor activity. In vivo single unit extracellular recording showed that pregabalin had mixed effects on dopamine (DA) neuronal activity in the ventral tegmental area since it decreased the activity of 50% of neurons and increased 28.5% of them. In contrast, cocaine decreased 75% of VTA DA neuronal activity whereas none of the neurons were activated. Intracerebal microdialysis was then conducted in awake freely mice to determine to what extent such electrophysiological parameters influence the extracellular DA concentrations ([DA]ext) in the nucleus accumbens. Although pregabalin failed to modify this parameter, cocaine produced a robust increase (800%) in [DA]ext.

CONCLUSIONS

Collectively, these electrophysiological and neurochemical experiments suggest that the rewarding properties of pregabalin result from a different mode of action than that observed with cocaine. Further experiments are warranted to determine whether such undesirable effects can be potentiated under pathological conditions such as neuropathic pain, mood disorders, or addiction and to identify the key neurotransmitter system involved.

Rising pregabalin use and misuse in Australia: trends in utilization and intentional poisonings

BACKGROUND AND AIMS

Pregabalin is a gamma-aminobutyric acid (GABA) analogue, used to treat neuropathic pain and epilepsy. Pregabalin was registered in Australia in 2005, and subsidized publically in 2013. We aimed to describe Australian patterns of pregabalin use and intentional poisoning, and identify people potentially at high risk of misuse.

DESIGN AND SETTING

Population-based retrospective cohort study of dispensings in the 10% sample of Australian Pharmaceutical Benefits Scheme (July 2012-February 2017); intentional poisoning calls to New South Wales Poisons Information Centre (NSWPIC) (2004-2016); intentional poisonings in two Australian toxicology service databases; and poisoning fatalities in NSW coronial records (2005-2016).

PARTICIPANTS

A total of 122 572 people dispensed pregabalin, people with intentional pregabalin overdoses managed by NSWPIC and the toxicology services and pregabalin-associated deaths referred to the NSW coroner.

MEASUREMENTS

Trends in dispensing, poisoning, death; demographics and patient characteristics, proportion of users at high risk of misuse (latent class analysis, LCA) and characteristics of high-risk users.

FINDINGS

Pregabalin dispensing increased by 73 424 per year [95% confidence interval (CI) = 61726-85 121 P < 0.001] between 2013 and 2016. NSWPIC received 1158 reports of intentional pregabalin poisonings, with a 53.8% increase per year, 2005-2016 (95% CI = 44.0-64.2%, P < 0.001). We identified 88 pregabalin-associated deaths, 57.8% yearly increase (95% CI = 30.0-91.6%, P < 0.001). Patients overdosing on pregabalin commonly co-ingested opioids, benzodiazepines and illicit drugs, and had high rates of psychiatric and substance use comorbidities; 14.7% of pregabalin users were classed by the LCA as at high risk of misuse, and were more likely to be younger, male, co-prescribed benzodiazepines or opioids, have more individual prescribers and higher pregabalin strengths dispensed.

CONCLUSIONS

There has been a dramatic increase in pregabalin use, poisonings and deaths in Australia since it became subsidized publicly in 2013. One in seven Australians dispensed pregabalin appears to be at high risk of misuse.

Misuse and Mortality Related to Gabapentin and Pregabalin are Being Under-Estimated: A Two-Year Post-Mortem Population Study

Due to the rise in their misuse and associated mortality, the UK government is reclassifying gabapentin (GBP) and pregabalin (PGL) to Class C controlled drugs from April 2019. However, it is impossible to gauge the extent of their use with current post-mortem toxicological screening, where GBP and PGL are only screened for if they are mentioned in the case documents. This study determines the prevalence of GBP and PGL, the potential extent of their under-reporting and poly-drug use in a post-mortem population. Between 1 January 2016 and 31 December 2017, 3,750 deceased from Coroners’ cases in London and South East England underwent a routine drugs screen and a specific screen for GBP and PGL. The prevalence of both drugs was determined in the cohort and the subcategories of heroin users and non-heroin-users. The prevalence of both drugs was compared to tramadol (Class C drug). Case documents were reviewed to investigate the under-reporting of GBP and PGL and poly-drug use. Of 3,750 samples analyzed, 118 (3.1%) were positive for GBP, 229 (6.1%) for PGL and 120 (3.2%) were positive for tramadol. If routine analysis without additional screening of GBP and PGL had been performed in this cohort, GBP would have been under-reported by 57.6% (P < 0.0001) and PGL by 53.7% (P < 0.0001) in deaths. The most common drug group observed with GBP and PGL was non-heroin-related opioids at 60.2% and 64.6%, respectively. In total 354 deceased (9.4%) were heroin users. GBP was positive in 23 (6.5%) of these cases and PGL was positive in 69 (19.5%). The prevalence of PGL in heroin users (19.5%) was 4.1 times greater than in non-heroin users (4.7%) (P < 0.0001). GBP and PGL are being significantly under reported in fatalities. Both drugs are extensively used with opioids. The prevalence of PGL in heroin users is highly significant.

Patterns and history of prescription drug use among opioid-related drug overdose cases in British Columbia, Canada, 2015-2016

BACKGROUND

British Columbia is the epicenter of the current fentanyl-related overdose crisis in Canada. Our study characterizes prescribing histories of people who had an opioid-related overdose compared to matched controls.

METHODS

We examined linked administrative data for individuals who overdosed between January 1, 2015 and November 30, 2016. Past prescriptions over five years were assessed for opioids for pain, opioid agonist therapy, benzodiazepines/z-drugs, antidepressants, antipsychotics, gabapentinoids, mood stabilizers and anti-epileptics, muscle relaxants, and other sedating medications. Prescribing history of 9964 cases was compared with that of 49,820 matched controls.

RESULTS

Overdose cases were more likely to be prescribed opioids for pain and to have used prescription opioids on a long-term basis in the previous five years compared to controls. However, at the time of overdose, 92% of men and 86% of women did not have an active opioid for pain prescription, and approximately half had not filled one in the past five years. Those who overdosed tended to have more prescriptions for psychotropic substances than controls. Fewer than 10% of cases had an active prescription for opioid agonist therapy and most were not on treatment in the past.

CONCLUSIONS

Low prevalence of active prescriptions for opioids for pain at the time of overdose suggests that opioid prescribing plays a limited short-term impact in the current fentanyl-related crisis of overdoses. While liberal opioid prescribing practices may have contributed to the development of the current overdose crisis, regulation and enforcement of clinicians' prescribing practices will likely have limited impact in reducing overdoses.

Gabapentin use, abuse, and the US opioid epidemic: the case for reclassification as a controlled substance and the need for pharmacovigilance

The abuse potential of gabapentin is well documented; with gabapentin having been noted as an agent highly sought after for use in potentiating opioids. When combined with opioids, the risk of respiratory depression and opioid-related mortality increases significantly. In the US, gabapentin was approved by the Food and Drug Administration as a non-controlled substance. To date, and in spite of empirical evidence suggestive of diversion and abuse with opioids, gabapentin remains a non-controlled substance at the federal level. This has forced individual US states and jurisdictions – often significantly impacted by the opioid epidemic – to forge ahead with legislative initiatives designed to reclassify and/or monitor the use of gabapentin. Since August 1, 2016, 14 of 51 US states and jurisdictions have either implemented legislative mandates requiring pharmacovigilance programs, amended rules and regulations, are in the throes of crafting policy, or are in the midst of gathering additional data for decision making. This fragmented geographic approach yields only a modest benefit in combating the abuse of gabapentin and/or the national opioid epidemic. Herein, we report state-by-state efforts to enhance pharmacovigilance and call for a re-evaluation of the schedule status of gabapentin at the federal level, and design and implementation of a national pharmacovigilance program.

Intentional Drug Overdose Involving Pregabalin and Gabapentin: Findings from the National Self-Harm Registry Ireland, 2007-2015

INTRODUCTION

Intentional drug overdose (IDO) is a significant public health problem. Concerns about the misuse of gabapentinoids, i.e. pregabalin and gabapentin, including their consumption in IDO have grown in recent years. This paper examines the trends in the prevalence of gabapentinoids taken in IDO, the profile of individuals taking them, and associated overdose characteristics.

METHODS

Presentations to emergency departments involving IDO, recorded by the National Self-Harm Registry Ireland between 1 January 2007 and 31 December 2015 were examined. Data items included patient demographics, drug names, total tablet quantity consumed and alcohol involvement.

RESULTS

Gabapentinoids were involved in 2115 (2.9%) of the 72,391 IDOs recorded. Presentations involving a gabapentinoid increased proportionally from 0.5% in 2007 to 5.5% in 2015. The majority of IDOs involving a gabapentinoid were made by females (59.9%), with over one-third (37.2%) involving alcohol. Compared with IDOs involving other drugs, presentations with a gabapentinoid were made by persons who were older (median 37 vs. 32 years) and involved a significantly greater median quantity of tablets (30 vs. 21, p ≤ 0.001), with over one-quarter (27.4%) of these involving the ingestion of 50 tablets or more. Admission to hospital was significantly more common following IDOs with a gabapentinoid compared with those without (49.4% vs. 41.4%, p ≤ 0.001).

CONCLUSIONS

This study identified the increasing use of gabapentinoids in IDO, describing the profile and overdose characteristics of presentations. It is important for clinicians to exercise vigilance while prescribing gabapentinoids, including being aware of other medications that their patients may have access to. Our findings support the need for routine monitoring for signs of misuse among those prescribed gabapentinoids.

Reports of gabapentin and pregabalin abuse, misuse, dependence, or overdose: An analysis of the Food And Drug Administration Adverse Events Reporting System (FAERS)

BACKGROUND

Reports of gabapentinoid (gabapentin and pregabalin) misuse have increased in recent years. Pharmacovigilance data from the Food and Drug Administration Adverse Event Reporting System (FAERS) provides a useful examination of adverse drug event (ADE) reporting for safety signal detection.

OBJECTIVE

This study was conducted to analyze epidemiological information on the nature and extent of gabapentin/pregabalin abuse utilizing the FAERS database.

METHODS

A query was designed utilizing SafeRx, an indexed, searchable database of FAERS data from October 2012-December 2016. All-cause and abuse-related (including abuse/misuse/dependence/overdose events) ADE reports for gabapentin and pregabalin were isolated, as well as limited demographic data. The proportional reporting ratio (PRR) was calculated to compare signal detection.

RESULTS

A total of 10,038 all-cause ADEs were reported to FAERS for gabapentin, including 576 (5.7%) abuse-related events. For pregabalin, 571 all-cause ADEs were identified, including 58 (10.2%) related to abuse. Compared to all-cause ADEs, those involved in abuse-related events were younger and more likely to be male. The PRR of pregabalin versus gabapentin abuse-related events was 1.77.

CONCLUSION

Though not traditionally thought of as drugs of abuse, over 600 cases of gabapentinoid abuse were reported in the time frame analyzed, prompting the need for further study and regulatory investigation.

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.