Gabapentin-Induced Neurologic Toxicities

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.

Top 100 Most-Cited Papers in Herpes Zoster from 2000 to 2022: A Bibliometric Study

Background

In recent years, the incidence of herpes zoster has risen steeply, the exact pathogenesis of the acute pain and the transformation into postherpetic neuralgia are still obscure, and the absence of effective management remains a major therapeutic challenge. The purpose of this study was to perform a qualitative and quantitative bibliometric analysis of the 100 most cited papers on herpes zoster.

Materials and methods

Related literature were retrieved from the Web of Science Core Collection. Excel and VOSviewer software were applied to quantitatively analyze, and construct the bibliometric network charts.

Results

The Top 100 most-cited papers published between 2000 and 2018 showed a fluctuating downward trend. The most studies were published in the year of 2000 (n = 12). The article entitled "A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults" from Oxman MN, was the most-cited publication. The United States was the most contributing country, followed by the United Kingdom, and Italy. Finland occupied the highest citations per publication (CPP). The University of Colorado topped the list of institutions with the most publications with 18 articles and also had the most citations (average citations: 281.78 per article). Myron J Levin from the University of Colorado School of Medicine is the most published and most cited researcher overall, whereas Duke University's John W Gnann tops the list in terms of average CPP.

Conclusion

In terms of the quantity of T100 articles, researchers, and organizations, the US is the predominant country. The most T100 papers were published in the special journal Clinical Infectious Diseases. The most academic focus remain the remedies for postherpetic neuralgia and vaccine development for individualized groups.

Treatment of Pain in Rats, Mice, and Prairie Dogs

Recent myomorph and scuiromorph rodent analgesia studies are reviewed and evaluated for potential clinical application. Differences between laboratory animal studies and clinical use in diseased animals are discussed. Analgesia classes reviewed include local anesthetics, nonsteroidal anti-inflammatories, acetaminophen, opioids, and adjuvants such as anticonvulsants. Routes of administration including sustained-release mechanisms are discussed, as are reversal agents. Drug interactions are reviewed in the context of beneficial multimodal analgesia as well as potential adverse effects. Dosage recommendations for clinical patients are explored.

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).

Toxin-Induced Coma and Central Nervous System Depression

Many medications and toxins may induce central nervous system (CNS) depression. Even when the intention is to induce CNS depression, other nervous system adverse effects may occur, such as with anesthetics. Pain medications produce characteristic CNS toxicities. Sedative hypnotics may induce altered mentation among systemic toxicities. Stimulants may mimic coma when discontinued abruptly. Acute and chronic carbon monoxide poisoning can lead to altered mental status and prolonged cognitive difficulties. Some medications and environmental toxins can mimic brain death. High clinical suspicion and early recognition of these effects is vital to treatment, most of which is supportive.

Managing the patient with epilepsy and renal impairment

PURPOSE

Epilepsy affects more than 50 million people worldwide and its management can be complicated by comorbidities such as impaired renal function. To optimize epilepsy control in patients with kidney disease, clinicians need to be aware of how antiepileptic drugs (AEDs) are affected by impaired renal function and how the kidneys are affected by epilepsy management strategies. Herein we present a narrative review with systematic literature search to discuss the use of AEDs in patients with renal impairment, including those undergoing dialysis, as well as the nephrotoxic effects of some AEDs. We finally conclude the article by providing practical tips about our approach to using AEDs in the setting of renal disease.

METHODS

A literature search targeting epilepsy management in patients with kidney disease was performed in MEDLINE database (1946 to 7th Jan 2019).

RESULTS

A total of 1193 articles were found. After duplicate removal, title and abstract screening followed by full text screening, a total of 110 references were included in this review. Additional information was included from drug product monographs.

CONCLUSION

The disposition of AEDs can be altered in patients with impaired renal function, leading to a higher risk of AED toxicity or therapy failure. Renal dosage adjustment and close monitoring is recommended. Although AED-induced nephrotoxicity is rare, it is unpredictable and clinicians need to vigilant about this possibility. In addition, AEDs renal adverse reactions and renal drug interactions should be considered when selecting an AED.

Neurologic Complications of Commonly Used Drugs in the Hospital Setting

This chapter reviews the neurologic complications of medications administered in the hospital setting, by class, introducing both common and less common side effects. Detail is devoted to the interaction between pain, analgesia, sedation, and their residual consequences. Antimicrobials are given in nearly every hospital setting, and we review their capacity to produce neurologic sequelae with special devotion to cefepime and the antiviral treatment of human immunodeficiency virus. The management of hemorrhagic stroke has become more complex with the introduction of novel oral anticoagulants, and we provide an update on what is known about reversal of the new oral anticoagulants. Both central and peripheral nervous system complications of immunosuppressants and chemotherapies are reviewed. Because diagnosis is generally based on clinical acumen, alone, neurotoxic syndromes resulting from psychotropic medications may be easily overlooked until severe dysautonomia develops. We include a practical approach to the diagnosis of serotonin syndrome and neuroleptic malignant syndrome.

Effects of NB001 and gabapentin on irritable bowel syndrome-induced behavioral anxiety and spontaneous pain

Irritable bowel syndrome (IBS) is characterized by recurrent abdominal discomfort, spontaneous pain, colorectal hypersensitivity and bowel dysfunction. Patients with IBS also suffer from emotional anxiety and depression. However, few animal studies have investigated IBS-induced spontaneous pain and behavioral anxiety. In this study, we assessed spontaneous pain and anxiety behaviors in an adult mouse model of IBS induced by zymosan administration. By using Fos protein as a marker, we found that sensory and emotion related brain regions were activated at day 7 after the treatment with zymosan; these regions include the prefrontal cortex, anterior cingulate cortex, insular cortex and amygdala. Behaviorally, zymosan administration triggered spontaneous pain (decreased spontaneous activities in the open field test) and increased anxiety-like behaviors in three different tests (the open field, elevated plus maze and light/dark box tests). Intraperitoneal injection of NB001, an adenylyl cyclase 1 (AC1) inhibitor, reduced spontaneous pain but had no significant effect on behavioral anxiety. In contrast, gabapentin reduced both spontaneous pain and behavioral anxiety. These results indicate that NB001 and gabapentin may inhibit spontaneous pain and anxiety-like behaviors through different mechanisms.

Gabapentin Therapy of Hiccups

OBJECTIVE:

To determine whether gabapentin is effective in the treatment of persistent or intractable hiccups.

DATA SOURCES:

A search of MEDLINE (1966-March 2013) using the MeSH search terms gabapentin, hiccups, and hiccups/drug therapy was performed. Additional databases searched included Web of Science (1945-March 2013) and International Pharmaceutical Abstracts (1970-March 2013) using the text words gabapentin and hiccups. Bibliographies of relevant articles were reviewed for additional citations.

STUDY SELECTION AND DATA EXTRACTION:

All data sources were considered for inclusion. Preference was given for articles written in English, although one abstract in German was used.

DATA SYNTHESIS:

Because of the low incidence of persistent or intractable hiccups, few if any controlled clinical trials are conducted on the efficacy of drug treatment. Therefore, most of the data involve case reports or case series. We evaluated 17 case reports and 2 case series involving gabapentin therapy for persistent or intractable hiccups. Therapeutic outcomes with gabapentin were positive in all cases, with temporal evidence suggesting an effect, but outcomes often were obscured by combination therapy and comorbidities in some cases. Case reports suggest that gabapentin might be useful as a second-line agent in patients undergoing stroke rehabilitation or in the palliative care setting where chlorpromazine adverse effects are undesirable. Gabapentin was very well tolerated, with only a few minor adverse effects.

CONCLUSIONS:

Gabapentin has a similar body of evidence as other pharmacotherapeutic agents used to treat hiccups. Gabapentin is well tolerated and should be considered as a second-line agent in selected patients.

Implications and mechanism of action of gabapentin in neuropathic pain

Gabapentin is an anti-epileptic agent but now it is also recommended as first line agent in neuropathic pain, particularly in diabetic neuropathy and post herpetic neuralgia. α2δ-1, an auxillary subunit of voltage gated calcium channels, has been documented as its main target and its specific binding to this subunit is described to produce different actions responsible for pain attenuation. The binding to α2δ-1 subunits inhibits nerve injury-induced trafficking of α1 pore forming units of calcium channels (particularly N-type) from cytoplasm to plasma membrane (membrane trafficking) of pre-synaptic terminals of dorsal root ganglion (DRG) neurons and dorsal horn neurons. Furthermore, the axoplasmic transport of α2δ-1 subunits from DRG to dorsal horns neurons in the form of anterograde trafficking is also inhibited in response to gabapentin administration. Gabapentin has also been shown to induce modulate other targets including transient receptor potential channels, NMDA receptors, protein kinase C and inflammatory cytokines. It may also act on supra-spinal region to stimulate noradrenaline mediated descending inhibition, which contributes to its anti-hypersensitivity action in neuropathic pain.

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.

Gabapentin toxicity in patients with chronic kidney disease: a preventable cause of morbidity

BACKGROUND

Gabapentin is frequently used as an analgesic in patients with chronic kidney disease. Although gabapentin is well known for its favorable pharmacokinetics, it is exclusively eliminated renally, and patients with chronic kidney disease are at risk for toxicity. Existing literature on such risk is lacking.

METHODS

We examined the Mayo Clinic Rochester database from 1998 to 2007 in patients with serum gabapentin measurements and known medical outcomes. A total of 729 patients were stratified according to their estimated glomerular filtration rate: group I, 126 individuals with estimated glomerular filtration greater than 90 mL/min/1.72 mm(2) [corrected] ; group II, 594 individuals with estimated glomerular filtration less than 90 mL/min/1.72 mm(2) [corrected] without dialysis; group III, 9 individuals with chronic dialysis.

RESULTS

Patients in groups II and III had higher serum gabapentin levels (8.39+/-0.32 microL/mL and 58.8+/-10.22 microL/mL, respectively) than in group I (5.52+/-0.32 microL/mL, P<.01). Toxicity occurred exclusively in groups II (5.56%) and III (77.8%); toxic manifestations were more severe in group III than in group II. Elderly individuals with multiple comorbidities were overrepresented in those with toxic manifestations. Gabapentin toxicity was suspected initially in only 41.5% of symptomatic cases.

CONCLUSION

Gabapentin toxicity in patients with chronic kidney disease is underrecognized. Patients with chronic kidney disease often receive inappropriately high gabapentin dosage for their kidney function, occasioning overt toxicity; advanced age and comorbidity predispose these patients for toxicity. Heightened awareness of such preventable risk, amid the chronic kidney disease epidemic, would be cost-effective and improve healthcare quality.

Gabapentin-induced delirium and dependence

Gabapentin (Neurontin) is approved by the US Food and Drug Administration for treatment of epilepsy and post-herpetic neuralgia. Despite lack of strong evidence, gabapentin is also often prescribed off-label for psychiatric conditions. The case described here involved a 38-year-old male physician with substance intoxication delirium and psychoactive substance dependence due to high self-administered doses of gabapentin, which had been prescribed at lower doses in combination with buspirone and bupropion for depression and anxiety. This unusual case of gabapentin dependence and abuse involved toxic delirium, intense cravings, and a prolonged post-withdrawal confusional state reminiscent of benzodiazepine withdrawal. Gabapentin is a central nervous system inhibitory agent with likely gamma-aminobutyric acid (GABA)-ergic and non-GABAergic mechanisms of action. The similarity between benzodiazepine withdrawal and what this patient experienced with gabapentin suggests a common role for GABA-related effects. The case reported here suggests the need for heightened concern regarding the off-label prescription of this drug to vulnerable individuals with psychiatric conditions.

A probable case of gabapentin-related reversible hearing loss in a patient with acute renal failure

BACKGROUND

As described in the literature, gabapentin toxicity in patients with impaired renal function can manifest as coma, myoclonus, tremulousness, or altered mental status. Gabapentin is an antiepileptic agent indicated for use as an adjunct therapy in partial seizures and postherpetic neuralgia but is also prescribed for the treatment of diabetic peripheral neuropathy.

CASE SUMMARY

A 46-year-old white woman (height, 167 cm; weight, 177 kg; body mass index, 62.8 kg/m2) with a 6-year history of diabetes mellitus and previously normal renal function, presented to the emergency department of Wake Forest University Baptist Medical Center with anuria (a serum creatinine level of 7.4 mg/dL), hearing loss, myoclonus, and confusion with hallucinations lasting for 3 days. Her blood pressure was 110/74 mm Hg. The patient's preadmit medication list included: lisinopril (40 mg QD), hydrochlorothiazide (25 mg QD), and furosemide (80 mg QD) for hypertension; atorvastatin (10 mg QD) for hyperlipidemia; omeprazole (20 mg QD) for gastroesophageal reflux disease; salmeterol/fluticasone inhaler (100/50 microg; 1 puff BID) and albuterol metered-dose inhaler (90 microg as needed) for asthma; metformin (500 mg BID) and insulin lispro per sliding scale for type 2 diabetes mellitus; oxycodone controlled release (60 mg TID) for chronic osteoarthritis and low back pain; alprazolam (0.5 mg every 8 hours as needed) for generalized anxiety disorder; venlafaxine (150 mg BID) for depression; and gabapentin (300 mg TID) for diabetic peripheral neuropathy. The patient's symptoms (hearing loss, myoclonus, and confusion) improved after 1 session of hemodialysis (approximately 10 hours following admission) and had resolved at the time of discharge (4 days later). On admission, the gabapentin concentration was 17.6 microg/mL, and following hemodialysis, the gabapentin concentration was undetectable (by discharge/day 4). The timing of the patient's last dose of gabapentin is unknown. Normal doses for the treatment of diabetic peripheral neuropathy range from 900 to 3600 mg/d divided 3 times daily.

CONCLUSIONS

We report a patient with acute renal failure who developed hearing loss, myoclonus, and confusion with hallucinations in the presence of elevated gabapentin concentrations. Due to rapid improvement after hemodialysis and discontinuation of gabapentin, we believe that these symptoms were probably due to gabapentin toxicity.

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.

Use of gabapentin in the treatment of behavioural and psychological symptoms of dementia: a review of the evidence

Behavioural and psychological symptoms of dementia (BPSD) have been defined as a heterogeneous range of psychological reactions, psychiatric symptoms and behaviours that may be unsafe, disruptive and impair the care of a patient in a given environment. To date, there are no US FDA-approved drugs or clear standards of pharmacological care for the treatment of BPSD. The novel antiepileptic agent gabapentin is being increasingly considered for use in the geriatric population because of its relatively favourable safety profile compared with other classes of psychiatric medications. Gabapentin has been administered to several geriatric patients with bipolar disorder and patients with dementia. It has also been reported to be successful in the treatment of a 13-year-old boy with behavioural dyscontrol, a finding that suggested a possible role for gabapentin in the treatment of other behavioural disorders. The purpose of this review was to find evidence for the use of gabapentin in the treatment of BPSD. To this end, a search was performed for case reports, case series, controlled trials and reviews of gabapentin in the treatment of this condition. The key words 'dementia', 'Alzheimer's disease' and 'gabapentin' were used. Searches were performed in PubMed, PsycINFO, Ovid MEDLINE, Cochrane Library and ClinicalTrials.gov. The search revealed that there are limited data on the efficacy of gabapentin for BPSD in the form of 11 case reports, 3 case series and 1 retrospective chart review; no controlled studies appear to have been published to date on this topic. In most of the reviewed cases, gabapentin was reported to be a well tolerated and effective treatment for BPSD. However, two case reports in which gabapentin was used in the context of agitation in dementia with Lewy bodies questioned the appropriateness of gabapentin for all types of dementia-related agitation. The dearth of available data limits support for the off-label use of gabapentin for the treatment of BPSD. Furthermore, controlled studies should be conducted before gabapentin can be clinically indicated for the successful treatment of BPSD.