Self-poisoning with lamotrigine and pregabalin

Rise of Pregabalin Poisoning and Abuse Cases in Serbia: A Ten-Year Retrospective Study

Purpose

The aim of this study was to analyze data on gabapentinoid-related attendances to the National Poison Control Center of Serbia (NPCC), particularly abuse cases; to estimate its changes and to compare it with trends in national consumption rates of these drugs. We also aimed to analyze the main characteristics of the study population and to investigate the major clinical effects in poisoned patients.

Patients and Methods

This is a retrospective study of patients admitted to the NPCC for acute poisoning involving gabapentinoids from 1 May 2012 to 1 October 2022.

Results

There were 357 (95.5%) pregabalin-related and 17 (4.5%) gabapentin-related poisoning cases in 302 patients. Abuse of pregabalin was detected in 27.8% (84/302), while gabapentin abuse occurred in 0.7% (2/302) of all patients. A steady increase in rates of pregabalin poisoning and abuse cases strongly correlated with the increase in overall consumption of this drug, while there were no significant changes in rates of gabapentin consumption, poisoning and abuse rate during the study period. Most patients who abused pregabalin pregabalin were males (84.5%) and the median age was 26 years (range: 15-45 years). Almost 60% of patients who abused pregabalin (48/84) belonged to the migrant population. Co-ingestions occurred in 89.4% of pregabalin-related cases (319/357), resulting in more severe poisoning. The most often co-ingested drugs were benzodiazepines and among them clonazepam was detected in the largest number of cases.

Conclusion

The poisoning and abuse cases involving pregabalin are on the rise in Serbia, which coincided with an increase in its overall consumption during the study period. Isolated pregabalin ingestions resulted in mild poisoning, although severe symptoms such as coma and bradycardia were recorded. When prescribing pregabalin to patients at risk of abuse caution is needed. Strengthening the measures for dispensing of pregabalin may reduce the risks associated with its abuse.

The assessment of cardiac risk in patients taking lamotrigine; a systematic review

OBJECTIVE

The Food and Drug Administration (FDA) warned about lamotrigine's arrhythmogenicity based on in vitro data. This systematic review investigates lamotrigine's effect on cardiac conduction and risk of sudden cardiac death (SCD) in individuals with and without cardiovascular disease.

METHODS

We searched Web of Science and PubMed from inception through August 2021. We included studies measuring electrocardiogram (ECG) changes, laboratory abnormalities, or SCD among patients taking lamotrigine. Studies examining sudden unexpected death in epilepsy were excluded for scope. Two reviewers assessed articles and extracted data. We used the Effective Public Healthcare Panacea Project tool to evaluate confidence in evidence.

RESULTS

Eight randomized controlled trials, 9 nonrandomized observational studies, and 24 case reports were identified, with >3054 total participants, >1606 of whom used lamotrigine. One randomized trial of older patients found an average QRS increase of 3.5 +/- 13.1 ms. Fifteen studies reported no changes in ECG parameters. Case reports documented QRS widening (13), Brugada syndrome (6), QTc prolongation (1) and SCD (2), though many ingested toxic quantities of lamotrigine and/or other medications.

CONCLUSIONS

Evidence is insufficient to support the breadth of the FDA warning concerning lamotrigine's cardiac risk. Lamotrigine at therapeutic doses may be associated with modest, non-dangerous QRS widening.

Chronic Pregabalin Abuse with Subacute Encephalopathy Mimicking Autoimmune Encephalitis

Pregabalin, a gabapentinoid frequently prescribed for neuropathic pain, also increasingly identified as a drug for abuse. We describe a unique case of 31-year-old man presented with subacute neuro-psychiatric symptoms and a spectrum of movement disorders, suspicious of autoimmune encephalitis. Initial response to IV methylprednisolone followed by recurrence of symptoms strengthened our suspicion for autoimmune encephalitis. His autoimmune encephalitis workup was negative, however, his two MRIs showed parenchymal changes. The patient, finally, confessed to chronic pregabalin abuse. He recovered completely upon stopping pregabalin abuse and remained asymptomatic at follow-up. To the best of our knowledge, we are the first to describe parenchymal changes in MRI mimicking autoimmune encephalitis in a case of pregabalin abuse. Despite the limited number of reports of pregabalin abuse in India, it is time to consider restricting the pregabalin availability, in line with many Western countries. This is particularly relevant to India, where, one legitimate prescription can be used by many to buy medicines at multiple stores without any questions being asked by the pharmacists.

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).

Pregabalin poisoning and rising recreational use: a retrospective observational series

AIMS

With rising use worldwide, pregabalin is increasingly implicated in poisoning deaths. We aimed to investigate the clinical effects and complications of pregabalin poisoning.

METHODS

This is a retrospective review of patients presenting with pregabalin poisoning to two tertiary toxicology units from 1 July 2014 to 30 June 2019. Patients were identified from prospective databases maintained by both units and data were extracted from these in addition to medical records.

RESULTS

There were 488 presentations in 413 patients (237 [57%] male) over the five-year period. The median age was 41 years (IQR 31-50 years). Deliberate self-poisonings accounted for 342 (70%) presentations, with 121 (25%) recreational exposures. Recreational exposures increased over the period from 2 (4%) in the first year to 54 (39%) presentations in the final year. The median dose of pregabalin was 1200 mg (IQR 600-3000 mg, range 75-16 800 mg). Co-ingestions occurred in 427 (88%) presentations, with sedating agents being co-ingested in 387 (79%)-most commonly opioids and benzodiazepines in 201 (41%) and 174 (36%) presentations respectively. Coma (GCS < 9) occurred in 89 (18%) cases, with 52 (11%) patients being intubated. Only one (0.2%) of these patients had not co-ingested a sedating agent. Hypotension occurred in 26 (5%) cases, all with co-ingestants. Seizures occurred in 11 (2%) cases, 3/59 (5%) in pregabalin-only overdoses. The median length of stay was 16.5 hours (IQR 10-25 hours).

CONCLUSIONS

Pregabalin overdose does not cause severe toxicity, but rather mild sedation and, uncommonly, seizures. Coma is common in the presence of sedating co-ingestants. Recreational use is increasing.

Pregabalin Misuse and Abuse: A Scoping Review of Extant Literature

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

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.

Rhabdomyolysis after lamotrigine overdose: a case report and review of the literature

BACKGROUND

Lamotrigine is an effective anticonvulsant drug that has also been demonstrated to be effective in the treatment of bipolar disorder. We report a case of rhabdomyolysis after intentional overdose in a woman aged 48.

CASE PRESENTATION

A 48-year-old female presented to the emergency department after an acute ingestion of 6 g of lamotrigine. The patient suffered from bipolar disorder, and she was taking lamotrigine and olanzapine. At that point, she had a major depressive episode, and she wanted to commit suicide. Activated charcoal was administered in the emergency department. Her vital signs were still normal, and she entered the Medical clinic, where she had been there for 2 days in a good condition. The hematological and biochemical results were normal. On the fourth day, the levels of creatine phosphokinase (CPK) showed remarkable increase (2500 IU/ml). Fluid and bicarbonate intravenous administration was performed, and CPK levels returned to normal after 3 days.

CONCLUSION

The majority of patients exposed to lamotrigine in overdose experienced no toxic clinical effects. The most common clinical effects are drowsiness and lethargy, vomiting, nausea, ataxia, dizziness/vertigo, and tachycardia. In this case report, the patient was alert and did not have any serious complications, except for mild rhabdomyolysis, which was the main consequence of lamotrigine overdose.

Efficacy and safety of pregabalin in generalised anxiety disorder: A critical review of the literature

The aim of this review is to summarise the literature on the efficacy and safety of pregabalin for the treatment of generalised anxiety disorder (GAD). Of 241 literature citations, 13 clinical trials were identified that were specifically designed to evaluate the efficacy and safety of pregabalin in GAD, including 11 randomised double-blind trials and two open-label studies. Pregabalin efficacy has been consistently demonstrated across the licensed dose range of 150-600 mg/day. Efficacy has been reported for pregabalin monotherapy in elderly patients with GAD, patients with severe anxiety, and for adjunctive therapy when added to a selective serotonin reuptake inhibitor or serotonin-norepinephrine reuptake inhibitor in patients who have failed to respond to an initial course of antidepressant therapy. The two most common adverse events with pregabalin are somnolence and dizziness, both of which appear to be dose-related. Pregabalin appears to have a low potential for causing withdrawal symptoms when long-term therapy is discontinued; however, tapering over the course of at least one week is recommended. A review of available evidence indicates that pregabalin is a well-tolerated and consistently effective treatment for GAD, with a unique mechanism of action that makes it a useful addition to the therapeutic armamentarium.

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.

Quantification of pregabalin using hydrophilic interaction HPLC-high-resolution MS in postmortem human samples: eighteen case reports

Pregabalin is a drug for treating epilepsy, anxiety disorders and neuropathic pain. Cases of poisoning are rare, though some have been fatal. Concentrations of pregabalin in postmortem human samples and its distribution have very rarely been documented. As the literature is so scarce, we propose to report the concentrations in autopsy samples of 18 people who had been taking Lyrica(®), including one case of a mixed overdose involving pregabalin. Analysis was carried out using an original Hydrophilic Interaction LIquid Chromatography (HILIC) technique coupled with a high-resolution mass spectrometer (m/z 160.1334 ± 5 ppm). The sensitivity of the technique enables a quick and simple treatment of the samples by protein precipitation. The method was validated in the whole blood with detection and quantification limits of 0.025 and 0.060 µg/mL, respectively. Pregabalin was a likely factor in the cause of death in 3 of the 18 cases. In the other individuals, the concentrations ranged from 0.4 to 17.0 in the peripheral blood, 1.5 to 11.1 in the central blood, 126.6 to 2004.6 in the urine and 10.5 to 58.3 µg/mL in the bile, with median values of 5.6, 4.6, 534.6 and 17.7, respectively.

Lamotrigine Versus Pregabalin in the Management of Refractory Trigeminal Neuralgia: A Randomized Open Label Crossover Trial

BACKGROUND

Carbamazepine (CBZ) formed the gold standard drug in trigeminal neuralgia (TN) treatment but faces high therapeutic failure. This defined the need to explore a second line of drug therapy. The study aimed at comparing two alternate drugs i.e. Lamotrigine (LTG) and Pregabalin (PGB), in the management of TN refractory to therapeutic doses of CBZ.

METHODS

Twenty-two patients with diagnosis of refractory TN were enrolled and randomly allotted into 2 groups of 11 each. Each group was subjected to a crossover analysis using LTG and PGB together with CBZ, for a period of 6 weeks. Patients maintained a pain diary, the scores of which, along with global evaluation scores, determined the primary outcome. Reevaluation of symptoms after 6 months was done to assess long term efficacy with study drugs.

RESULTS

Both LTG and PGB were effective over CBZ alone (p < 0.05); however, statistically insignificant difference (p > 0.05) was observed between the two groups using Mann-Whitney tests. Unlike LTG, side effects like nausea, insomnia and concentration loss were minimal with PGB thus exhibiting greater patient compliance. Secondary analysis showed complete relief in 4 patients on PGB (mean dose 240.68 mg/day) while 6 had partial relief. Three patients on LTG (mean dose 310.90 mg/day) reported relapse of acute symptoms and required peripheral alcohol blocks.

CONCLUSION

Pregabalin has potential anti-neuralgia properties comparable to LTG. However, the level of patient's tolerance seen with PGB exceeds that with LTG. 6 months follow-up records suggest that PGB together with CBZ offers a more reliable pain control than with LTG.

Significant pregabalin toxicity managed with supportive care alone

There are two previously reported cases describing the management of pregabalin self-poisoning and one further case of management of therapeutic pregabalin accumulation. The peak reported pregabalin concentrations in these cases ranged from 13 mg/L to approximately 60 mg/L. Previous case reports have suggested that both supportive care and enhanced elimination are appropriate managements for pregabalin toxicity. A 54-year-old male presented following ingestion of 8.4 g of pregabalin. Initially, he had no clinical features of toxicity, although he developed significant neurological depression and coma approximately 3 h post-ingestion. He was managed with supportive care (including endotracheal intubation and mechanical ventilation) until his level of consciousness improved. Subsequent toxicological screening confirmed isolated pregabalin ingestion, with a serum pregabalin concentration of 66.5 mg/L at the time he clinically deteriorated. The pharmacokinetic properties of pregabalin indicate the potential value of extra-corporeal elimination methods such as haemodialysis. Clinical toxicologists should be aware that whilst there is a pharmacokinetic basis for the use of extra-corporeal methods in those with severe toxicity arising from excessive plasma pregabalin concentrations, there are case reports, including this one, where patients have been managed with supportive measures only.

Suicidality in people taking antiepileptic drugs: What is the evidence?

Suicide is an important cause of premature death. In the general population, most people who commit suicide have a psychiatric problem at the time. People with epilepsy are thought to be at increased risk from suicide and suicidality (suicidal ideation or behaviour). Standardized mortality ratios estimated for suicide in people with epilepsy are usually between 3 and 5. Risk factors for suicide in people with epilepsy have been suggested, including early age of onset of seizures, temporal lobe epilepsy, severe seizures and recent control of seizures. Psychiatric co-morbidity also seems to be an important factor in people with epilepsy who commit suicide. In recent years, suicidality has been recognized as a complication of several groups of drugs and, most recently, antiepileptic drugs (AEDs) have been implicated. The US FDA performed a meta-analysis of 199 placebo-controlled studies of 11 AEDs used for seizure control, psychiatric or 'other' indications. There were four completed suicides in those taking AEDs and none in those taking placebo. The odds ratio for suicidal behaviour or ideation was 1.8 (95% CI 1.24, 2.66), suggesting that people taking AEDs are more at risk than those taking placebo. The odds ratio was significantly raised for people taking AEDs for epilepsy, but not for the other indications. AEDs may affect mood by means of several mechanisms. In people with epilepsy, however, the concept of forced normalization (or alternative psychosis) may also play a part. In this situation, control of seizures (by AEDs or epilepsy surgery) may alternate with psychotic features or, less commonly, depression, although this is not fully understood. The risk of suicidal ideation and behaviour as adverse effects of AED treatment, although increased, seems low. As a result of the FDA's alert clinicians are supposed to inform patients and their families of this increased risk but it is important to place it in a proper perspective. Some people with epilepsy are more likely to develop psychiatric adverse effects with any AEDs, and these people should be followed closely whenever a new AED is introduced. Nonetheless, in people with epilepsy the risk of suicidality associated with AEDs needs to be balanced against the risk of not treating the seizures. In fact, the risk of stopping AEDs or refusing to start AEDs for the control of a seizure disorder may be significantly worse and may result in serious harm, including death of the patient.

Lamotrigine does not prolong QTc in a thorough QT/QTc study in healthy subjects

AIM

To characterize the effects of lamotrigine on QT interval in healthy subjects.

METHODS

Healthy subjects received a single oral dose of moxifloxacin (400 mg) or placebo in crossover design, followed by a dose-escalating regimen of lamotrigine (n = 76) over a 77-day period, or matched placebo (n = 76). Blood samples were taken for determination of moxifloxacin and lamotrigine concentrations and digital 12-lead ECGs were recorded. The relationships between individual QT values and respective individual moxifloxacin or lamotrigine concentrations were explored using population pharmacokinetic-pharmacodynamic (PK-PD) modelling.

RESULTS

Moxifloxacin was associated with a maximum mean increase from baseline in QTcF of 14.81 ms [90% confidence interval (CI) 13.50, 16.11] 2.5 h after dosing. Steady-state exposure to lamotrigine (50, 150 or 200 mg b.d.) was not associated with an increase in QTc interval. Small reductions in QTcF (maximum mean difference from placebo -7.48 ms, 90% CI -10.49, -4.46) and small increases in heart rate (maximum mean difference from placebo 5.94 bpm, 90% CI 3.81, 8.06) were observed with lamotrigine 200 mg b.d. vs. placebo. No effect of lamotrigine on QRS duration or blood pressure was observed. No outliers with QTcF > 450 ms, or with an increase from baseline of >60 ms were observed in the lamotrigine group. PK-PD modelling indicated statistically significant decreases in individually corrected QT intervals for lamotrigine and statistically significant increases in individually corrected QT intervals for moxifloxacin over the concentration ranges studied.

CONCLUSIONS

Therapeutic doses of lamotrigine (50-200 mg b.d.) were not associated with QT prolongation in healthy subjects.