Characterization of gabapentin overdose using a poison center case series

Effects of Acute and Chronic Gabapentin Treatment on Cardiovascular Function of Rats

Gabapentin (GBP), a GABA analogue, is primarily used as an anticonvulsant for the treatment of partial seizures and neuropathic pain. Whereas a majority of the side effects are associated with the nervous system, emerging evidence suggests there is a high risk of heart diseases in patients taking GBP. In the present study, we first used a preclinical model of rats to investigate, firstly, the acute cardiovascular responses to GBP (bolus i.v. injection, 50 mg/kg) and secondly the effects of chronic GBP treatment (i.p. 100 mg/kg/day × 7 days) on cardiovascular function and the myocardial proteome. Under isoflurane anesthesia, rat blood pressure (BP), heart rate (HR), and left ventricular (LV) hemodynamics were measured using Millar pressure transducers. The LV myocardium and brain cortex were analyzed by proteomics, bioinformatics, and western blot to explore the molecular mechanisms underlying GBP-induced cardiac dysfunction. In the first experiment, we found that i.v. GBP significantly decreased BP, HR, maximal LV pressure, and maximal and minimal dP/dt, whereas it increased IRP-AdP/dt, Tau, systolic, diastolic, and cycle durations (* p < 0.05 and ** p < 0.01 vs. baseline; n = 4). In the second experiment, we found that chronic GBP treatment resulted in hypotension, bradycardia, and LV systolic dysfunction, with no change in plasma norepinephrine. In the myocardium, we identified 109 differentially expressed proteins involved in calcium pathways, cholesterol metabolism, and galactose metabolism. Notably, we found that calmodulin, a key protein of intracellular calcium signaling, was significantly upregulated by GBP in the heart but not in the brain. In summary, we found that acute and chronic GBP treatments suppressed cardiovascular function in rats, which is attributed to abnormal calcium signaling in cardiomyocytes. These data reveal a novel side effect of GBP independent of the nervous system, providing important translational evidence to suggest that GBP can evoke adverse cardiovascular events by depression of myocardial function.

Concurrent Gabapentin and Opioid Use and Risk of Mortality in Medicare Recipients with Non-Cancer Pain

Gabapentin is prescribed for pain and is perceived as safe generally. However, gabapentin can cause respiratory depression, exacerbated by concomitant central nervous system depressants (e.g., opioids), a concern for vulnerable populations. We compared mortality rates among new users of either gabapentin or duloxetine with or without concurrent opioids in the 20% Medicare sample. We conducted a new-user design retrospective cohort study, in Medicare enrollees ages 65-89 years with noncancer chronic pain and no severe illness who filled prescriptions between 2015 and 2018 for gabapentin (n = 233,060) or duloxetine (n = 34,009). Daily opioid doses, estimated in morphine milligram equivalents (MMEs), were classified into none, low (0 < MME < 50), and high (≥ 50 MME), based on Centers for Disease Control and Prevention (CDC) recommendations. The outcomes were all-cause mortality (primary) and out-of-hospital mortality (secondary). We used inverse probability of treatment weighting to adjust for differences between gabapentin and duloxetine users. During 116,707 person-years of follow-up, 1,379 patients died. All-cause mortality rate in gabapentin users was 12.16 per 1,000 person-years vs. 9.94 per 1,000 in duloxetine users. Risks were similar for users with no concurrent opioids (adjusted hazard ratio (aHR) = 1.03, 95% confidence interval (CI): 0.80-1.31) or low-dose daily opioids (aHR = 1.06, 95% CI: 0.63-1.76). However, gabapentin users receiving concurrent high-dose daily opioids had an increased rate of all-cause mortality compared with duloxetine users on high-dose opioids (aHR = 2.03, 95% CI: 1.19-3.46). Out-of-hospital mortality yielded similar results. In this retrospective cohort study of Medicare beneficiaries, concurrent use of high-dose opioids and gabapentin was associated with a higher all-cause mortality risk than that for concurrent use of high-dose opioids and duloxetine.

Gabapentin-Associated Movement Disorders: A Literature Review

BACKGROUND

Gabapentin (GBP)-induced movement disorders (MDs) are under-recognized adverse drug reactions. They are commonly not discussed with patients, and their sudden occurrence can lead to misdiagnosis. This literature review aims to evaluate the clinical-epidemiological profile, pathological mechanisms, and management of GBP-associated MD.

METHODS

Two reviewers identified and assessed relevant reports in six databases without language restriction between 1990 and 2023.

RESULTS

A total of 99 reports of 204 individuals who developed a MD associated with GBP were identified. The MDs encountered were 135 myoclonus, 22 dyskinesias, 7 dystonia, 3 akathisia, 3 stutterings, 1 myokymia, and 1 parkinsonism. The mean and median ages were 54.54 (SD: 17.79) and 57 years (age range: 10-89), respectively. Subjects were predominantly male (53.57%). The mean and median doses of GBP when the MD occurred were 1324.66 (SD: 1117.66) and 1033 mg/daily (GBP dose range: 100-9600), respectively. The mean time from GBP-onset to GBP-associated MD was 4.58 weeks (SD: 8.08). The mean recovery time after MD treatment was 4.17 days (SD: 4.87). The MD management involved GBP discontinuation. A total of 82.5% of the individuals had a full recovery in the follow-up period.

CONCLUSIONS

Myoclonus (GRADE A) and dyskinesia (GRADE C) were the most common movement disorders associated with GBP.

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).

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.

Association of gabapentinoid utilization with postoperative pulmonary complications in gynecologic surgery: a retrospective cohort study

OBJECTIVE

To investigate gabapentinoid utilization and association with postoperative pulmonary complications after gynecologic surgery.

METHODS

After Institutional Review Board approval, we performed this retrospective cohort study using the Premier Healthcare Database. We used ICD-10 and charge codes to identify adults who underwent elective gynecologic surgery from 2015 to 2018 and received either gabapentin or pregabalin on the day of surgery. Our primary outcome was a composite of pulmonary complications: respiratory failure, pneumonia, reintubation, pulmonary edema, and non-invasive or invasive ventilation. Secondary outcomes included mortality, intensive care unit admission, mechanical or non-invasive ventilation, hospital length of stay, re-admission within 30 days, opioid consumption and antiemetic use. Multivariable generalized linear mixed models were utilized to examine the associations between gabapentinoids and our outcome measures, adjusted for all covariates.

RESULTS

Data from 253,013 patients were analyzed, with 19,121 (7.6%) receiving gabapentinoids. Gabapentinoid utilization increased from 3.9% in 2015 to 12.3% in 2018, and was associated with increased pulmonary complications (OR 1.19; 95% CI 1.03-1.38), non-invasive ventilation (odds ratio [OR] 1.53; 95% CI 1.29-1.81), duration of hospital stay (% change 1.75; 95% CI 0.92-2.59), daily antiemetic doses on day of surgery (mean difference [MD] 1.37; 95% CI 1.26-1.49) and subsequently (MD 1.61; 95% CI 1.30-1.99), and higher daily average (MD 4.59 mg; 95% CI 3.55-5.63) and total (MD 8.74 mg; 95% CI 6.83-10.62) parenteral morphine equivalents.

CONCLUSIONS

Gabapentinoid utilization in gynecologic surgery is increasing and is associated with postoperative pulmonary complications.

Respiratory depression in the post-anesthesia care unit: Mayo Clinic experience

The anesthesia recovery is a complex physiologic process as systems recover from the effects of surgery and anesthesia. Inadequate recovery of respiratory physiology can lead to severe hypoxemia-induced end-organ damage and even death. Emerging evidence suggests that signs of respiratory depression during early anesthesia recovery may portend increased risk for future severe adverse events. This article briefly reviews the Mayo Clinic research experience and advances in clinical practice. From the implementation of a step-down model of discharge criteria in the post-anesthesia care unit (PACU), consisting of PACU nurses monitoring patients in predetermined periods for signs of respiratory depression, and delaying PACU discharge for patients who exhibit signs of respiratory depression, and early intervention in high-risk patients. Subsequent studies found that even a single episode of respiratory depression in the PACU was strongly associated with subsequent respiratory complications. Further, patient baseline characteristics found to be associated with respiratory depression included obstructive sleep apnea and low body weight, and surgical factors associated with increased risk included the use of preoperative sustained-release opioids, perioperative gabapentinoid use, higher intraoperative opioids, isoflurane as the volatile anesthetic, and longer surgical duration. Based in part of Mayo Clinic research, the FDA issued a warning in 2019 on gabapentinoids use and respiratory complications, increasing the recommended level of respiratory vigilance in patients using this medication. Understanding the complex nature of postoperative respiratory events requires a range of translational and clinical research and constant update of practice.

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.

Unintentional exposure to pregabalin in ≤6-year-old children: a nationwide French Poison Control Center study

INTRODUCTION

In France, pregabalin is widely prescribed in adults but still not approved for children. We aimed to investigate the incidence of pregabalin exposure in ≤6-year-old children, to describe the characteristics and outcome of ingestions involving pregabalin alone, and to estimate a clinically relevant toxic dose in this population.

METHODS

Retrospective analysis of pregabalin exposures in ≤6-year-old children, collected by the French Poison Control Centers in 2004-2019. The incidence was estimated using pregabalin prescription data from the Health Improvement Network database (the French version of THIN). The poison severity score (PSS) was used to grade severity.

RESULTS

We found 313 unintentional immediate-release pregabalin ingestions in ≤6-year-old children. The number of cases per 100,000 pregabalin-treated adults increased over time (p < 0.001). One hundred twenty-six cases involving pregabalin alone (age, 2 years [1.6-3.0] (median [25th-75th percentiles]); median ingested dose 6.4 mg/kg [3.6-10.9]) were analyzed. No child presented an underlying neurological/cardiac disease and/or took concomitant medications. Most of the children (77%) remained asymptomatic (PSS0) while 21% and 2% developed minor (PSS1) or moderate (PSS2) neurological symptoms, respectively. No severe complications/fatalities were reported. All symptomatic children recovered within 24 h. The ingested pregabalin dose was positively correlated with PSS (p < 0.0001). Using a ROC curve approach (area under the curve, 0.85; p < 0.001), ingestion of ≥19.4 mg/kg pregabalin was appropriate to recommend hospital referral (sensitivity, 39% [95% confidence interval (95% CI), 24-56], specificity, 100% [95% CI, 96-100], predictive positive value, 100% [95% CI, 64-100], and negative predictive value, 85% [95% CI, 82-89]). Symptomatic children who ingested <19.4 mg/kg pregabalin developed minor symptoms.

CONCLUSION

Despite increasing prescriptions in adults in France, unintentional pregabalin ingestions in ≤6-year-old children remain rare and cause minimal toxicity. Children with no underlying neurological/cardiac disease and concomitant medication ingesting <19.4 mg/kg immediate-release pregabalin alone can be safely observed at home.

Multimorbidity and Critical Care Neurosurgery: Minimizing Major Perioperative Cardiopulmonary Complications

With increasing prevalence of chronic diseases, multimorbid patients have become commonplace in the neurosurgical intensive care unit (neuro-ICU), offering unique management challenges. By reducing physiological reserve and interacting with one another, chronic comorbidities pose a greatly enhanced risk of major postoperative medical complications, especially cardiopulmonary complications, which ultimately exert a negative impact on neurosurgical outcomes. These premises underscore the importance of perioperative optimization, in turn requiring a thorough preoperative risk stratification, a basic understanding of a multimorbid patient’s deranged physiology and a proper appreciation of the potential of surgery, anesthesia and neurocritical care interventions to exacerbate comorbid pathophysiologies. This knowledge enables neurosurgeons, neuroanesthesiologists and neurointensivists to function with a heightened level of vigilance in the care of these high-risk patients and can inform the perioperative neuro-ICU management with individualized strategies able to minimize the risk of untoward outcomes. This review highlights potential pitfalls in the intra- and postoperative neuro-ICU period, describes common preoperative risk stratification tools and discusses tailored perioperative ICU management strategies in multimorbid neurosurgical patients, with a special focus on approaches geared toward the minimization of postoperative cardiopulmonary complications and unplanned reintubation.

Multimodal Pain Management and Postoperative Outcomes in Lumbar Spine Fusion Surgery: A Population-based Cohort Study

STUDY DESIGN

Retrospective population-based cohort analysis.

OBJECTIVE

Given the lack of large-scale data on the use and efficacy of multimodal analgesia in spine fusion surgery, we conducted a population-based analysis utilizing the nationwide claims-based Premier Healthcare database.

SUMMARY OF BACKGROUND DATA

Multimodal analgesia, combining different pain signaling pathways to achieve additive and synergistic effects, is increasingly emerging as the standard of care.

METHODS

Cases of posterior lumbar fusion surgery were extracted (2006-2016). Opioid-only analgesia was compared to multimodal analgesia, that is, systemic opioid analgesia + either acetaminophen, steroids, gabapentinoids, ketamine, nonsteroidal anti-inflammatory drugs (NSAIDs), cyclooxygenase-2 (COX-2) inhibitors, or neuraxial anesthesia (categorized into 1, 2, or >2 additional analgesic modes). Mixed-effects models measured associations between multimodal analgesia categories and outcomes, including opioid prescription dose, cost/length of hospitalization, and opioid-related complications. Odds ratios (ORs, or % change) and 95% confidence intervals (CIs) are reported.

RESULTS

Among 265,538 patients the incidence of multimodal analgesia was 61.1% (162,156); multimodal pain management-specifically when adding NSAIDs/COX-2 inhibitors to opioids-was associated with reduced opioid prescription (-13.3% CI -16.7 to -9.7%), cost (-2.9% CI -3.9 to -1.8%) and length of hospitalization (-7.3% CI -8.5 to -6.1%). Multimodal analgesia in general was associated with stepwise decreased odds for gastrointestinal complications (OR 0.95, 95% CI 0.88-1.04; OR 0.84, CI 0.75-0.95; OR 0.78, 95% CI 0.64-0.96), whereas odds were increased for postoperative delirium (OR 1.14, 95% CI 1.00-1.32; OR 1.33, 95% CI 1.11-1.59; OR 1.31, 95% CI 0.99-1.74), and counterintuitively- naloxone administration (OR 1.25, 95% CI 1.13-1.38; OR 1.56, 95% CI 1.37-1.77; OR 1.84, 95% CI 1.52-2.23) with increasing analgesic modes used: one, two, or more additional analgesic modes, respectively. Post-hoc analysis revealed that specifically gabapentinoid use increased odds of naloxone requirement by about 50%, regardless of concurrent opioid dose (P < 0.001).

CONCLUSION

Although multimodal analgesia was not consistently implemented in spine fusion surgery, particularly NSAIDs and COX-2 inhibitors demonstrated opioid sparing effects. Moreover, results suggest a synergistic interaction between gabapentinoids and opioids, the former potentiating opioid effects resulting in greater naloxone requirement.

LEVEL OF EVIDENCE

3.

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.

A case of gabapentin overdose induced rhabdomyolysis requiring renal replacement therapy

We report a rare case with gabapentin overdose that caused severe rhabdomyolysis and acute tubular necrosis which required renal replacement therapy. A better awareness of its adverse effect and a close follow-up of laboratory tests are recommended. Prescribers should also be aware of high-risk population and monitor for signs of abuse.

Non-Hormonal Replacement Therapy Regimens: Do they have an Effect on Cardiovascular Risk?

INTRODUCTION

Menopause is associated with adverse effects on quality of life of perimenopausal and post-menopausal women. It also has an impact on the development of cardiovascular disease (CVD). Hormonal treatments are the most effective medications for menopausal symptoms relief. Given the fact that hormonal treatments are contraindicated for many women, non-hormonal treatment, such as Selective Serotonin Reuptake Inhibitors (SSRIs), Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs), gabapentin, pregabalin, clonidine and phytoestrogens, constitute alternative treatments. Nevertheless, little is known about their effects on CVD risk.

METHODS

PubMed, EMBASE and Cochrane Library were searched for the effects of non-hormonal treatment on CVD risk, blood pressure, heart rate, lipids and glucose concentrations, weight gain, cardiovascular events, stroke, mortality and morbidity.

RESULTS

Phytoestrogens, pregabalin and gabapentin seem to have no adverse effects on the cardiovascular system. Phytoestrogens, in particular, seem to reduce CVD risk through many pathways. On the other hand, SSRIs and SNRIs, although effective in reducing menopausal vasomotor symptoms, should be cautiously administered to women with known CVD (e.g. with cardiac arrhythmias, atherosclerotic disease or stroke). As clonidine has been associated with cardiovascular adverse effects, it should be administered only in cases where blood pressure regulation is mandatory.

CONCLUSION

Further research is needed to produce definite conclusions regarding the cardiovascular safety of non-hormonal medications for menopausal symptoms relief.

Antiepileptic drugs: Role in paediatric poisoning

Intoxications, both accidental and intentional, are common in children and adolescents and often require hospitalisation and intensive treatment. Antiepileptic drugs are a possible cause of poisoning and intoxications because this category of medications has shown a rising trend in recent years. They might be responsible for multi-organ dysfunctions of variable severity, ranging from subtle symptoms to life-threatening complications. No guidelines on the management of these intoxications in the paediatric population are currently available, and treatment is mainly supportive. Activated charcoal administration and extracorporeal circulation techniques for drug removal have been proposed. Facing the complexity of this clinical scenario, it is of utmost importance to maintain a high index of suspicion to guarantee a prompt intervention and ensure the best possible management for the patient.

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.

Law enforcement-derived data on gabapentin diversion and misuse, 2002-2015: diversion rates and qualitative research findings

PURPOSE

Recent limited epidemiologic and case reports suggest that gabapentin is being misused, especially among prescription opioid misusers. However, no apparent studies have reported data from law enforcement on the diversion and misuse of gabapentin.

METHODS

Case report data are drawn from a quarterly survey of prescription drug diversion completed by a national sample of law enforcement and regulatory agencies who engage in drug diversion investigations. Rates of gabapentin diversion per 100 000 population were calculated for each quarter from 2002 through 2015. Qualitative data are drawn from a brief questionnaire completed by a subsample of survey respondents and were organized and presented by theme.

RESULTS

In total, 407 new cases of diverted gabapentin were reported during the time period, with diversion rates steadily increasing from zero cases in the first 2 quarters of 2002 to a high of 0.027 cases per 100 000 population in the fourth quarter of 2015. Qualitative data suggest that gabapentin is being misused in conjunction with prescription opioids and that gabapentin and heroin are being combined and consumed together. Law enforcement reporters found these drug use trends to be contributing to gabapentin diversion.

CONCLUSIONS

The recent increase in gabapentin diversion appears to be related to the opioid epidemic, based on law enforcement descriptions of gabapentin being misused in combination with opioids. Yet epidemiological data related to this finding is limited and research conducted among gabapentin misusers is needed to understand this problem in more depth. Greater monitoring of gabapentin abuse and diversion appear warranted.

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.

Clinical outcomes in newer anticonvulsant overdose: a poison center observational study

Clinicians have limited experience with assessment and treatment of overdose from newer anticonvulsant medications. The aim of this investigation was to evaluate clinical effects of newer anticonvulsant overdose, determine if a relationship exists between dose and clinical effect, and if a particular agent appears more toxic in overdose. This was a retrospective study using electronic poison center data, evaluating clinical outcomes from newer anticonvulsant overdose. The Toxicall™ database from January 1, 2002 to December 31, 2011 was queried using key words: "gabapentin," "lamotrigine," "levetiracetam," "tiagabine," "topiramate," "zonisamide," "pregabalin," and "oxcarbazine." Polypharmacy overdose and children less than 15 years of age were excluded. Charts were reviewed by two abstractors for pharmaceutical, self-reported dose, clinical effect score, and clinical signs, symptoms, and vital signs recorded in the chart. Ordinal logistic regression was used to evaluate the relationship between drug type, dose, age, and sex to clinical effect score. Out of 501 cases identified, 347 met the final inclusion criteria. There were 116 gabapentin, 67 lamotrigine, 15 levetiracetam, 15 tiagabine, 56 topiramate, 23 pregabalin, and 55 oxcarbazepine cases. Overdose of newer anticonvulsants frequently results in altered mental status. Seizures may be more common with tiagabine, lamotrigine, and oxcarbazepine. There was one death reported from intentional overdose of topiramate. An information index was created to rank drug toxicity based on reported signs and symptoms for each overdose. There was no significant effect of dose on severity of outcome (β = 0.12, p = 0.23). However, the risk of a more severe outcome score was significantly increased with tiagabine relative to other drugs (β = 2.8, p = 0.001). Lamotrigine ranked highest in terms of toxicity (HT = 1.66) and number of interventions performed (HI = 1.17), and levetiracetam the lowest (HT = 0.98; HI = 0.88). We could not identify a dose-effect in these data which likely reflects the limitations of self-reported doses. Despite limitations of these data, the risk of more severe outcome scores appear to be higher with tiagabine overdose while lamotrigine overdose appears to result in more reported signs, symptoms, and interventions.

The role of gabapentin in the management of alcohol withdrawal and dependence

OBJECTIVE

To review the literature evaluating gabapentin for alcohol withdrawal and dependence.

DATA SOURCES

A literature search of MEDLINE (1966 to end of March 2015) and PubMed was performed using the terms alcohol, gabapentin, withdrawal, and dependence. Additional references were identified from a review of literature citations.

STUDY SELECTION AND DATA EXTRACTION

English-language prospective studies evaluating gabapentin for alcohol withdrawal and dependence were evaluated.

DATA SYNTHESIS

A total of 10 publications utilizing gabapentin in alcohol withdrawal (n = 5) and alcohol dependence (n = 5) were included in this review. Limited data suggest that gabapentin can provide benefit in managing mild alcohol withdrawal syndrome. There were 5 reported or suspected seizures in the withdrawal studies, suggesting that additional safety data are necessary before gabapentin monotherapy can be routinely considered. Sleep and mood/anxiety-related outcomes were positively influenced by gabapentin, which may result in long-term benefits if continued beyond the withdrawal period for the treatment of alcohol dependence. Studies evaluating gabapentin for alcohol dependence demonstrated dose-dependent benefits for complete abstinence, rates of no heavy drinking, and cravings. Gabapentin used to treat alcohol dependence was well tolerated with no severe adverse reactions reported in the extant literature.

CONCLUSION

Gabapentin may have a role in the treatment of mild alcohol withdrawal, but future studies should focus on adequate dosing strategies. Gabapentin should be considered for the treatment of alcohol dependence when barriers prevent the use of traditional agents. Additional studies should be conducted to further validate findings from the research conducted to date, but the current literature is promising for gabapentin in the treatment of alcohol dependence.

A review on the efficacy and safety of gabapentin in the treatment of chronic cough

INTRODUCTION

Effective antitussives available to control cough are limited. Consolidation among different afferent branches of the vagus nerve is needed to bring about cough. A general, widely accepted view is that the chronic increase in the sensitivity of the cough reflex is associated with inflammatory hypersensitivity such as from gastro-esophageal reflux disease. There is increasing evidence that an important mechanism is a sensory disorder of the laryngeal branches of the vagus nerve. Neuromodulating drugs are effectively used in the treatment of chronic pain and neuropathic disorders and may have a role in the treatment of refractory chronic cough (CC).

AREAS COVERED

Current evidence on the efficacy and safety of gabapentin in the treatment of CC is reviewed. Relevant randomized controlled trials, case reports and reviews were identified through a PubMed search of English-language literature referring to cough, sensory neuropathy and gabapentin over the last 10 years.

EXPERT OPINION

Gabapentin appears to be effective and well tolerated in the treatment of CC and in other sensory neuropathic disorders. Relevant clinical trials investigating its efficacy and safety profile in the treatment of cough are limited and further studies are needed. Gabapentin has been shown to cause minimal to no toxicity in overdose.

Gabapentin for Substance Use Disorders: Is it Safe and Appropriate?

Gabapentin is effective for the treatment of alcohol dependence and can be used for treating anxiety, insomnia, headaches, and/or pain in patients who have comorbid substance use disorders (SUDs) or who are at high risk of substance abuse. Deaths from unintentional drug overdoses are increasing, are the leading cause of injury death in the United States, and are mostly attributable to prescription drugs, in particular opioid agents. Compared to other psychotropic drugs, gabapentin is not especially harmful or lethal. Gabapentin misuse is possible, similar to other medications not typically considered drugs of abuse, but it should be considered safe and appropriate for use in patients with all types of SUDs, including patients who take opioid drugs.

Perioperative gabapentinoids: choice of agent, dose, timing, and effects on chronic postsurgical pain

This article summarizes the current evidence for the use of gabapentinoids in the perioperative setting and provides useful clinical recommendations regarding dosing, timing, and choice of agent.

Suicide by gabapentin overdose

Gabapentin is an antiepileptic drug that is prescribed for both FDA-approved and multiple off-label conditions, and has a relatively safe side-effect profile. Rare cases of overdose-related adverse effects have been reported in the literature. Described herein are the circumstances and autopsy findings of a 62-year-old woman with a history of depression, whose death was caused by intentional ingestion of excess gabapentin. The postmortem peripheral blood gabapentin concentration as determined by high-performance liquid chromatography/tandem mass spectroscopy was 88 μg/mL. Previously reported cases of individuals surviving gabapentin overdoses are discussed and compared with this case. Based on a review of the available literature, this appears to be the first published report of a death due solely to gabapentin toxicity.

Lacosamide intoxication in attempted suicide

The anticonvulsant drug lacosamide selectively enhances slow inactivation of voltage-gated sodium channels and has been shown to be an effective add-on treatment for partial-onset seizures. Common adverse events (frequency 10%) of lacosamide doses up to 600 mg/day include nonspecific central nervous system effects (e.g., dizziness, ataxia, diplopia, and somnolence). There are no human data regarding the safety of very high dosages of lacosamide. We report the clinical course of a patient with bitemporal epilepsy who ingested 12 g of lacosamide, 56 g of gabapentin, 2g of topiramate, and 2.8 g of zonisamide during a suicide attempt. The patient was found comatose and experienced repeated generalized tonic-clonic seizures, aspiration with subsequent pneumonia, hypotension, and an increase in PR interval. Complete physical recovery occurred after several days of supportive treatment. We conclude that intoxication with lacosamide, in combination with overdoses of multiple AEDs, can be survived without sequelae, even after ingestion of 12 g lacosamide.

Gabapentin toxicity in renal failure: the importance of dose adjustment

OBJECTIVE

This case report outlines a significant type of morbidity due to continued use of gabapentin during an episode of acute renal failure. Setting. University teaching hospital.

DISCUSSION

Gabapentin is widely used in the management of pain. It is entirely excreted through the renal system so this needs to be considered in any patient becoming acutely ill and developing renal failure. We describe a patient who developed significant deterioration in her conscious level due to iatrogenic gabapentin overdose.

CONCLUSION

All doctors need to be aware of the need to review the indications for gabapentin use during periods of acute illness, especially with regard to renal impairment. Off-label use should be discouraged.

A randomized double-blind pilot trial of gabapentin versus placebo to treat alcohol dependence and comorbid insomnia

BACKGROUND

Insomnia and other sleep disturbances are common, persistent, and associated with relapse in alcohol-dependent patients. The purpose of this pilot study was to compare gabapentin versus placebo for the treatment of insomnia and prevention of relapse in alcohol-dependent patients.

METHODS

Twenty-one subjects, including 10 women who met study criteria for alcohol dependence and insomnia and expressed a desire to abstain from alcohol, were recruited to the study. During a 1 to 2 week placebo lead-in and screening phase, a complete medical history, physical exam, blood tests, urine drug test, and structured interviews were performed to determine eligibility and patterns of alcohol use and sleep. Insomnia due to intoxication or acute withdrawal, psychiatric or medical illness, medications, and other sleep disorders were ruled out. Subjects were then randomized to either placebo (n = 11) or gabapentin (n = 10) for 6 weeks and titrated over a 10-day period to 1,500 mg or 5 pills at bedtime. After a 4-day taper, subjects were reassessed 6 weeks after ending treatment.

RESULTS

Gabapentin significantly delayed the onset to heavy drinking, an effect which persisted for 6 weeks after treatment ended. Insomnia improved in both treatment groups during the medication phase, but gabapentin had no differential effects on sleep as measured by either subjective report or polysomnography.

CONCLUSION

Because gabapentin is a short-acting medication that was taken only at nighttime in this study, it may possibly exert a nocturnal effect that prevents relapse to heavy drinking by a physiological mechanism not measured in this pilot study.

Refractory shock and asystole related to tramadol overdose

INTRODUCTION

Tramadol use is largely considered safe. However, several lethal cases of tramadol intoxication were reported, suggesting an underestimated toxicity. We report for a tramadol overdose case in combination with other central nervous system depressants, leading to refractory shock requiring extracorporeal life support.

CASE REPORT

A 33-year-old man was admitted in our intensive care unit for drug intoxication with coma, seizures, and hypotension without signs of heart failure. A few hours later, he developed a ventricular tachycardia, followed by a brief cardiac arrest in asystole with refractory shock requiring an extracorporeal life support, vasopressors, and hemofiltration. With this aggressive support, his overall status gradually improved. Repeated echocardiography showed an improvement in the cardiac function. The patient was weaned off extracorporeal life support on day eight and discharged on day 12. On admission, a urine analysis, using gas chromatography-mass spectrometry, showed high peaks of tramadol and desmethyltramadol with the presence of hydroxyzine, gabapentine, and clonazepam. The tramadol blood concentration measured by the high-performance liquid chromatography method-diode array detector was 23.9 mg/L, much higher than many previously reported fatal overdoses. No other drugs with potential cardiac toxicity, such as beta-blockers, calcium antagonists, antiarrythmic, antidepressants, meprobamate, or other xenobiotics were detected.

CONCLUSION

This case illustrates that tramadol overdose may cause refractory shock and asystole when taken in combination with CNS depressants, and reminds all physicians to be vigilant with regard to the potential toxic effects of tramadol.

Self-poisoning with lamotrigine and pregabalin

We report a case of intentional overdose in a 29-year-old male with two of the newer anti-epileptic agents, lamotrigine and pregabalin. To our knowledge, this case report details the highest plasma levels of lamotrigine ever recorded in the literature. The patient presented with seizures and a reduced level of consciousness. Management of these and subsequent complications centres on supportive care in the high dependency and intensive therapy units.

Should Gabapentin Be Dose Adjusted: What are the Clinical Consequences?

Objective:

To review the clinical necessity of renal dose adjustment of gabapentin.

Data Sources:

Medical literature (1966–February 2006, week 2) was accessed through MEDLINE, EMBASE, Pre-MEDLINE, International Pharmaceutical Abstracts, and the manufacturer's package insert. Search terms included gabapentin, side effects/adverse effects, overdose, toxicity, and renal impairment. Literature references were consulted for relevant information.

Study Selection and Data Extraction:

All studies from the data sources that were published in English were evaluated. Case reports, case series, and clinical trials with primarily adult populations were included in the review to determine the clinical necessity of dosage adjustment, including morbidity and mortality associated with dose adjustment failure. Case reports of gabapentin overdose were evaluated for clinically significant outcomes. All reports were examined for clinical relevance and adequate information to address the issue of major clinical consequences of failure to dose adjust gabapentin in specific patient populations, including renally impaired and elderly patients.

Data Synthesis:

The package insert suggests dose adjustment of gabapentin in patients with decreased renal function, yet published information regarding clinical consequences of gabapentin in patients is limited. Although gabapentin possesses a favorable safety profile and is generally well tolerated, there have been cases reporting serious adverse effects. While clinical studies and the majority of case reports demonstrate minimal adverse effects, there is some concern that select patients may experience serious outcomes if the drug is not dose adjusted.

Conclusions:

The recommendation for dosage adjustment is suitably based upon the pharmacokinetic properties of gabapentin, yet healthcare practitioners should determine the need for gabapentin dosage adjustment in specific patients. There should be continued emphasis on recommending renal dose adjustments, with the most concern applied to the elderly and patients with significant renal impairment/end-stage renal disease.

A Randomized, Open-Label, Controlled Trial of Gabapentin and Phenobarbital in the Treatment of Alcohol Withdrawal

Gabapentin was compared with phenobarbital for the treatment of alcohol withdrawal in a randomized, open-label, controlled trial in 27 inpatients. There were no significant differences in the proportion of treatment completers between treatment groups or the proportion of patients in each group requiring rescue medication for breakthrough signs and symptoms of alcohol withdrawal. There were no significant treatment differences in withdrawal symptoms or psychological distress, nor were there serious adverse events. These findings suggest that gabapentin may be as effective as phenobarbital in the treatment of alcohol withdrawal. Given gabapentin's favorable pharmacokinetic profile, further study of its effectiveness in treating alcohol withdrawal is warranted.

Gabapentin-Induced Neurologic Toxicities

Gabapentin is an antiepileptic drug approved for the treatment of postherpetic neuralgia and as adjunctive therapy for partial seizures. The drug has been shown to be safe and nontoxic. The current literature has limited reports of neurologic toxicity associated with gabapentin therapy in patients with or without renal dysfunction. We describe the case of a 75-year-old man with renal dysfunction who developed neurologic toxicity due to gabapentin accumulation. Future studies are warranted to confirm the neurologic adverse effects of gabapentin, including any additional risks in patients with renal dysfunction.

Antiepileptic drugs and their impact on balance

Antiepileptic drugs (AEDs) are being used with increasing frequency, not only to manage epilepsy, but also in the treatment of other conditions including neuropathic pain, migraine headaches and psychiatric conditions requiring mood stabilization. Although AEDs as a class are commonly prescribed in older patients and those with a predisposition to imbalance, the effect these drugs exert on gait and equilibrium has received very little study. Data from controlled efficacy and safety trials suggests that some AEDs are more apt to affect balance than others, even at therapeutic doses. In particular, phenytoin, primidone and phenobarbital produce more dizziness than some of the newer AEDs such as lamotrigine, levetiracetam and oxcarbazepine. For some of the other new AEDs, the data are simply not sufficient to estimate their effect on balance. This article reviews the current evidence that may guide the clinician in choosing a medication likely to have a low impact on gait and balance. Considering the risks and morbidity associated with imbalance and falls, particularly in the elderly, the direct effects of AEDs on balance should be examined further.

The Effects of Intrathecal Gabapentin on Spinal Morphine Tolerance in the Rat Tail-Flick and Paw Pressure Tests

Analgesic tolerance to opioids has been described in both experimental and clinical conditions and may limit the clinical utility of these drugs. We have previously shown that systemic gabapentin (GBP), a non-opioid drug, prevents and reverses tolerance to systemic morphine in the rat. In this study, we investigated the effect of intrathecal GBP on spinal morphine tolerance. Studied rats were given 7 days of intrathecal injections with saline (10 microL), GBP (300 microg), morphine (15 microg), or a GBP-morphine combination, and analgesic testing using tail-flick and paw-pressure tests was conducted before and 30 min after the drug injection. On Day 8, an antinociceptive dose-response curve was constructed and the 50% effective dose (ED(50)) values for morphine (given alone) were calculated for each study group. Coinjection of GBP with morphine blocked the development of tolerance, as shown by the preservation of morphine analgesia over 7 days as well as by a concomitant decrease in ED(50) values on Day 8, as compared with the morphine-alone group. Although additive analgesia over Days 1-7 cannot be ruled out, ED(50) reductions in the GBP-morphine combination group indeed suggest some suppression of tolerance. These data support previous evidence that GBP prevents opioid tolerance and, more specifically, indicate that intrathecal GBP prevents the development of spinal opioid tolerance. Future studies are required to examine the respective roles of supraspinal and peripheral sites of GBP-morphine interaction and to investigate the mechanisms underlying the action of GBP on opioid tolerance.