Gabapentin-induced Multifocal Myoclonus

BACKGROUND

Gabapentin is the most commonly preferred agent for neuropathic pain in general practice as it is usually well tolerated, but occasionally, its toxicity may occur at standard doses, especially in elderly individuals, even without any prior comorbidities.

CASE

We present an elderly male with normal renal parameters, who was started on gabapentin for neuropathic pain. He developed multifocal myoclonus all over the body within few days after starting gabapentin and subsided completed after withdrawal of the drug.

CONCLUSION

Acute hyperkinetic movement disorders such as multifocal or segmental myoclonus in elderly patients warrant a prompt review of recent drug history, especially gabapentin, even in the background of normal renal function.

GABA Analogue HSK16149 in Chinese Patients With Diabetic Peripheral Neuropathic Pain: A Phase 3 Randomized Clinical Trial

Importance

Many patients with diabetic peripheral neuropathic pain (DPNP) experience inadequate relief, despite best available medical treatments. There are no approved and effective therapies for patients with DPNP in China.

Objective

To evaluate the efficacy and safety of capsules containing γ-aminobutyric acid (GABA) analogue HSK16149 in the treatment of Chinese patients with DPNP.

Design, Setting, and Participants

This phase 2 to 3 adaptive randomized clinical trial was multicenter, double blind, and placebo and pregabalin controlled. The trial started on December 10, 2020, and concluded on July 8, 2022. In stage 1, various doses of HSK16149 were evaluated to determine safety and efficacy for stage 2. The second stage then validated the efficacy and safety of the recommended dose.

Intervention

In stage 1, enrolled patients (n = 363) were randomized 1:1:1:1:1:1 to 4 HSK16149 doses (40, 80, 120, or 160 mg/d), pregabalin (300 mg/d), or placebo. In stage 2, patients (n = 362) were randomized 1:1:1 to receive HSK16149, 40 or 80 mg/d, or placebo. The final efficacy and safety analysis pooled data from patients receiving the same treatment.

Main Outcomes and Measures

The primary efficacy end point in stage 1 was the change from baseline in average daily pain score (ADPS) at week 5. The primary efficacy end point in stage 2 was the change from baseline in ADPS at week 13. When the final statistical analysis was performed, the P values calculated from the independent data of each phase were combined using the weighted inverse normal method to make statistical inferences.

Results

Of 725 randomized patients in the full-analysis set (393 men [54.2%]; mean [SD] age, 58.80 [9.53] years; 700 [96.6%] of Han Chinese ethnicity), 177 received placebo; 178, HSK16149, 40 mg/d; 179, HSK16149, 80 mg/d; 66, HSK16149, 120 mg/d; 63, HSK16149, 160 mg/d; and 62, pregabalin, 300 mg/d. A total of 644 patients (88.8%) completed the study. The 40- and 80-mg/d doses of HSK16149 were recommended in stage 2. At week 13, the ADPS mean (SD) change from baseline was -2.24 (1.55) for the 40-mg/d and -2.16 (1.79) for 80-mg/d groups and -1.23 (1.68) for the placebo group, showing statistical significance for both HSK16149 doses vs placebo (both P < .001). In a safety set (n = 726), 545 patients (75.1%) had adverse events, which were generally mild to moderate, with dizziness and somnolence being the most common.

Conclusions and Relevance

Forty- and eighty-mg/d doses of HSK16149 were recommended for treating patients with DPNP in China. The efficacy of HSK16149 capsules was superior to placebo in all groups for relieving DPNP and appeared well tolerated.

Trial Registration

ClinicalTrials.gov Identifier: NCT04647773.

Phenibutan-an Illegal Food Supplement With Psychotropic Effects and Health Risks

BACKGROUND

Phenibut (β-phenyl-γ-aminobutyric acid) is an analog of the neurotransmitter gamma-aminobutyric acid (GABA). Like abapentin and pregabalin, it inhibits α2-δ-subunits of voltagedependent presynaptic calcium channels. The potential harm resulting from the use of these gabapentinoids is currently a matter of debate.

METHODS

This review is based on pertinent publications retrieved by a selective literature search and on cases reported to the Giftinformationszentrum-Nord (GIZ-Nord), a poison information center at the University of Göttingen, Germany.

RESULTS

Phenibut is a prescription drug in Russia but its production, possession, use, trafficking, or administration is illegal in Germany. The phenibut toxicity syndrome resembles that of gabapentinoids and GABA mimetics: benzodiazepine-like with - drawal symptoms including epileptic seizures, delirium and paradoxical activation have been described, as have cases of abuse and dependence. A few cases of use in the setting of multidrug abuse, and of phenibut-related death, have been described to date in the USA. The GIZ-Nord received 17 inquiries about phenibut, 55 about gabapentin, and 126 about pregabalin over the period 2008-2022. Over the same period, the GIZ-Nord was informed of 1207 cases involving Z substances and 4324 involving benzodiazepines. In the majority of the registered intoxications, including those with phenibut, the symptoms were mild. Overdoses of phenibut (2-100 g) were reported in 15 of the 17 cases; 8 of the persons who had taken an overdose were somnolent. In such cases, observation in intensive care was recommended. Respiratory depression or coma was not encountered in any case, not even in the patient who had taken 100 g of phenibut.

CONCLUSION

Phenibut causes symptoms resembling those of gabapentinoid and benzodiazepine use. There have been reports of phenibut use in combination with other psychotropic drugs; in particular, its use together with opiates could increase the risk of coma and respiratory depression. No deaths due to phenibut intoxication have been published in Germany or elsewhere in Western Europe, although such cases may have been overlooked, as this drug is still largely unknown to Western medicine.

Gabapentin for Pain in Pediatric Palliative Care

OBJECTIVE

Gabapentin is commonly used to treat pain in children receiving pediatric palliative care. This study describes the real-world use of gabapentin and the associated benefits and adverse effects/events (AEs).

METHODS

A prospective, multicenter cohort of standardized data collection after a clinical decision was made to use gabapentin for managing neuropathic or nociplastic pain in children attended on by a pediatric palliative care service. It was conducted across 11 sites in seven countries including hospital, inpatient, and outpatient services. Clinical outcomes were graded using pain scales validated for age and cognitive ability and the National Cancer Institute Common Terminology Criteria for Adverse Events (NCICTCAE) at baseline, 14 days, 28 days, six weeks and 12 weeks after initiation of gabapentin. Ad-hoc safety reporting continued throughout the study.

RESULTS

Data were collected from 127 children with a median age of 4.7 years (IQR 0.1-17.9); 61% had a neurological disorder, 21% advanced cancer and the cohort had a high level of disability (Lansky/Karnofsky performance score 37.1). Gabapentin was prescribed at standard pediatric doses. On average, 76% of children had a reduction in pain and 42% experienced a potential AE. The mean pain score decreased from 6.0 (SD 2.6) at baseline to 3.3 (SD 2.4) at 14 days and 1.8 (SD 1.8) after 12-weeks of gabapentin therapy. Ten percent had increased pain at each time point. AEs did not increase when individual changes over time were accounted for except for somnolence (7%). Serious AEs attributable to gabapentin were possible or probable in 3% of children.

CONCLUSIONS

Gabapentin prescribed at standard doses for advanced cancer and severe neurological injury in children under a pediatric palliative care service was associated with generally improved pain intensity at previously described levels of adverse effects.

Safety and Efficacy of Gabapentin for Pain in Pediatric Patients: A Systematic Review

CONTEXT

Gabapentin has shown benefits for a variety of pain etiologies in adult patients, with off-label use as an adjunctive agent in pediatric patients occurring more frequently.

OBJECTIVES

To summarize the studies which evaluate safety and efficacy of gabapentin for the treatment of pediatric pain.

DATA SOURCES

A systematic review of the literature was conducted via PubMed query with controlled vocabulary and key terms using indexed medical subject heading.

STUDY SELECTION

Prospective studies published between January 1, 2000, and July 1, 2023, were selected utilizing a predetermined exclusion criteria independently by 2 authors, with a third independent author available for discrepancies.

DATA EXTRACTION

Data extraction was performed by 2 authors independently to include study design, patient population and characteristics, drug dosing, and outcomes. Studies were then assessed for their independent risk of bias utilizing the Grading of Recommendations, Assessment, Development, and Evaluations approach to risk of bias.

RESULTS

A total of 11 studies describing 195 pediatric patients who received gabapentin were included. Of the 11 studies, 9 were randomized controlled trials, 1 was a prospective multicenter study, and 1 was an open-label pilot study.

CONCLUSIONS

Heterogeneity of pain type and gabapentin dosing regimens within the included studies made conclusions difficult to quantify. Efficacy likely depends significantly on etiology of pain; however, per these studies, gabapentin is likely safe to use for a variety of pediatric patient populations as a multimodal agent.

Signal detection of adverse events associated with gabapentinoid use for chronic pain

INTRODUCTION

Gabapentinoids (GABA) prescribing as a potential and conceivably safer substitute for opioids has substantially increased. Understanding all potential adverse drug events (ADEs) associated with GABA will guide clinical decision-making for pain management.

METHODS

A 20% sample of Medicare enrollees with new chronic pain diagnoses in 2017-2018 was selected. GABA users were those with >=30 consecutive days prescription in a year without opioid prescription. Opioid users were similarly defined. The control group used neither of these drugs. Propensity score match across three groups based on demographics and comorbidity was performed. We used proportional reporting ratio (PRR), Gamma Poisson Shrinker, and tree-based scan statistic (TBSS) to detect ADEs within 3, 6, and 12 months of follow-up.

RESULTS

Immunity disorder was detected within 3 months of follow-up by PRR compared to opioid use (PRR:2.33), and by all three methods compared to controls. Complications of transplanted organs/tissues and schizophrenia spectrum/other psychotic disorders were consistently detected by PRR and TBSS within 3 months. Skin disorders were detected by TBSS; and stroke was detected by PRR within 3 months compared to opioid use (PRR:4.74). Some malignancies were detected by PRR within 12 months. Other signals detected in GABA users were neuropathy and nerve disorders.

CONCLUSIONS

Our study identified expected and unexpected ADE signals in GABA users. Neurological signals likely related to indications for GABA use. Signals for immunity, mental/behavior, and skin disorders were found in the FDA adverse event reporting system database. Unexpected signals of stroke and cancer require further confirmatory analyses to verify.

Usefulness of Gabapentin as an Alternative/Adjunct Therapy for Delirium: A Retrospective Observational Study

BACKGROUND

Antipsychotics are commonly used to treat delirium but can adversely affect the extrapyramidal and cardiac conduction systems. Antipsychotic use has also been reported to be associated with increased mortality in older adults. Therefore, alternative and adjunct medications for delirium are necessary. We retrospectively assessed the efficacy and safety of gabapentin (GBP) as an alternative and adjunct medication for delirium.

METHODS

We retrospectively investigated the records of patients with delirium treated with GBP (71 patients; median age, 81 years; interquartile range, 76-87.5 years; 54.9% males) at a general hospital. We examined duration to delirium improvement, as assessed by the Intensive Care Delirium Screening Checklist (ICDSC) and DSM-5 criteria, as well as adverse events.

RESULTS

The median (interquartile range) GBP dose was 200 mg (150-350 mg) /day. A total of 71.8% and 85.9% of the patients failed to meet the diagnostic criteria for delirium at 2 days and 5 days after initial administration, respectively (p<0.05). In subgroup analysis, patients with a history of epilepsy or cerebrovascular disease responded better to GBP than did those without such histories, suggesting that patients with abnormal/borderline neuronal activity respond to GBP even though they do not exhibit seizures. GBP did not induce extrapyramidal symptoms, cardiac conduction disturbances, hyperglycemia, or epilepsy but caused sleepiness and myoclonus.

CONCLUSIONS

GBP may improve delirium with fewer adverse effects and may be a safe alternative or adjunct treatment for delirium. Dosage adjustment may be necessary to prevent sleepiness.

Bidirectional Neuronal Control of Epileptiform Activity by Repetitive Transcranial Focused Ultrasound Stimulations

Repetitive stimulation procedures are used in neuromodulation techniques to induce persistent excitatory or inhibitory brain activity. The directivity of modulation is empirically regulated by modifying the stimulation length, interval, and strength. However, bidirectional neuronal modulations using ultrasound stimulations are rarely reported. This study presents bidirectional control of epileptiform activities with repetitive transcranial-focused ultrasound stimulations in a rat model of drug-induced acute epilepsy. It is found that repeated transmission of elongated (40 s), ultra-low pressure (0.25 MPa) ultrasound can fully suppress epileptic activities in electro-encephalography and cerebral blood volume measurements, while the change in bursting intervals from 40 to 20 s worsens epileptic activities even with the same burst length. Furthermore, the suppression induced by 40 s long bursts is transformed to excitatory states by a subsequent transmission. Bidirectional modulation of epileptic seizures with repeated ultrasound stimulation is achieved by regulating the changes in glutamate and γ-Aminobutyric acid levels, as confirmed by measurements of expressed c-Fos and GAD65 and multitemporal analysis of neurotransmitters in the interstitial fluid obtained via microdialysis.

Shared GABA transmission pathology in dopamine agonist- and antagonist-induced dyskinesia

Dyskinesia is involuntary movement caused by long-term medication with dopamine-related agents: the dopamine agonist 3,4-dihydroxy-L-phenylalanine (L-DOPA) to treat Parkinson's disease (L-DOPA-induced dyskinesia [LID]) or dopamine antagonists to treat schizophrenia (tardive dyskinesia [TD]). However, it remains unknown why distinct types of medications for distinct neuropsychiatric disorders induce similar involuntary movements. Here, we search for a shared structural footprint using magnetic resonance imaging-based macroscopic screening and super-resolution microscopy-based microscopic identification. We identify the enlarged axon terminals of striatal medium spiny neurons in LID and TD model mice. Striatal overexpression of the vesicular gamma-aminobutyric acid transporter (VGAT) is necessary and sufficient for modeling these structural changes; VGAT levels gate the functional and behavioral alterations in dyskinesia models. Our findings indicate that lowered type 2 dopamine receptor signaling with repetitive dopamine fluctuations is a common cause of VGAT overexpression and late-onset dyskinesia formation and that reducing dopamine fluctuation rescues dyskinesia pathology via VGAT downregulation.

Effectiveness of oral clonidine and gabapentin on peripheral neuropathy in diabetic patients in southwestern Iran: a randomized clinical trial

BACKGROUND

Peripheral neuropathy is not only the most prevalent consequence of diabetes but also the main reason for foot ulceration, disability, and amputation. Therefore, the current study aims to determine the effectiveness of oral clonidine and gabapentin on peripheral neuropathy in diabetic patients.

METHODS

This 12-week, randomized, and parallel-group trial was conducted to compare the efficacy of oral clonidine and gabapentin with gabapentin alone in diabetic patients in southwest Iran during the first half of 2021. Thirty patients with type 2 diabetes with peripheral neuropathy as assessed by a visual analog scale (VAS) and divided into two groups of 15 patients, treated for up to three months. The data were analyzed using SPSS-21 software. In order to report the results, descriptive indices, independent t-test, one-way analysis of covariance (ANCOVA) and analysis of variance with repeated measures were used.

RESULTS

The mean and standard deviation of the age of the participants in the clonidine + gabapentin group was equal to 50.20 ± 7.44, and in the gabapentin group was equal to 50.47 ± 7.57 (t = 0.10, P-value = 0.923). This research showed a significant difference between the clonidine + gabapentin group and with gabapentin group in terms of neuropathic pain and the severity of neuropathic pain (P < 0.001).

CONCLUSIONS

According to this research results, clonidine + gabapentin can reduce neuropathic pain and the severity of neuropathic pain in diabetic patients. Therefore, it is recommended that healthcare professionals with diabetes expertise prescribe these medications to reduce neuropathic pain and its severity.

TRIAL REGISTRATION

This study was registered in the Iranian Clinical Trials System with the ID (IRCT20211106052983N1) on 14/01/2022.

Abuse and addiction in gabapentinoid drug users for neuropathic pain

OBJECTIVE

Gabapentinoids are gamma-aminobutyric acid analogue agents used in the treatment of neuropathic pain. They are increasingly being abused to achieve euphoric and dissociative effects. This study aimed to determine drug misuse/abuse and related factors in patients who used gabapentinoids for neuropathic pain.

PATIENTS AND METHODS

This study included 140 patients over the age of 18. Patients were excluded from the study if they had aphasia, dementia, or diseases that led to aphasia or cooperative and cognitive dysfunction. They were also excluded if they lacked sufficient information about how long or at what dosage they had been using the drug. The Beck Depression Inventory and Beck Anxiety Inventory were used to evaluate depression and anxiety states. The patients' levels of drug abuse were determined according to the definitions provided in the terminology for misuse, abuse, and related events.

RESULTS

The mean age of the patients was 56.78 ± 14.45 years, and 52.1% of them were females. While 57.9% of the patients used pregabalin, 42.1% of the patients used gabapentin. For the median (min-max) of the dataset, the pregabalin dose was 300 (50-600) mg/day, and the gabapentin dose was 900 (300-2,400) mg/day. Abuse was present in 17.9% of the patients. Risk factors for gabapentinoid abuse were smoking, alcohol, and antidepressant use, anxiety and depression, living alone, and drug dose and duration of use.

CONCLUSIONS

Before prescribing drugs and managing the treatment process in a controlled manner, questioning patients about their risk factors can reduce the rate of abuse.

Treatment of cholinergic-induced status epilepticus with polytherapy targeting GABA and glutamate receptors

Despite new antiseizure medications, the development of cholinergic-induced refractory status epilepticus (RSE) continues to be a therapeutic challenge as pharmacoresistance to benzodiazepines and other antiseizure medications quickly develops. Studies conducted by Epilepsia. 2005;46:142 demonstrated that the initiation and maintenance of cholinergic-induced RSE are associated with trafficking and inactivation of gamma-aminobutyric acid A receptors (GABAA R) thought to contribute to the development of benzodiazepine pharmacoresistance. In addition, Dr. Wasterlain's laboratory reported that increased N-methyl-d-aspartate receptors (NMDAR) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR) contribute to enhanced glutamatergic excitation (Neurobiol Dis. 2013;54:225; Epilepsia. 2013;54:78). Thus, Dr. Wasterlain postulated that targeting both maladaptive responses of reduced inhibition and increased excitation that is associated with cholinergic-induced RSE should improve therapeutic outcome. We currently review studies in several animal models of cholinergic-induced RSE that demonstrate that benzodiazepine monotherapy has reduced efficacy when treatment is delayed and that polytherapy with drugs that include a benzodiazepine (eg midazolam and diazepam) to counter loss of inhibition, concurrent with an NMDA antagonist (eg ketamine) to reduce excitation provide improved efficacy. Improved efficacy with polytherapy against cholinergic-induced seizure is demonstrated by reduction in (1) seizure severity, (2) epileptogenesis, and (3) neurodegeneration compared with monotherapy. Animal models reviewed include pilocarpine-induced seizure in rats, organophosphorus nerve agent (OPNA)-induced seizure in rats, and OPNA-induced seizure in two mouse models: (1) carboxylesterase knockout (Es1-/- ) mice which, similarly to humans, lack plasma carboxylesterase and (2) human acetylcholinesterase knock-in carboxylesterase knockout (KIKO) mice. We also review studies showing that supplementing midazolam and ketamine with a third antiseizure medication (valproate or phenobarbital) that targets a nonbenzodiazepine site rapidly terminates RSE and provides further protection against cholinergic-induced SE. Finally, we review studies on the benefits of simultaneous compared with sequential drug treatments and the clinical implications that lead us to predict improved efficacy of early combination drug therapies. The data generated from seminal rodent studies of efficacious treatment of cholinergic-induced RSE conducted under Dr. Wasterlain's guidance suggest that future clinical trials should treat the inadequate inhibition and temper the excess excitation that characterize RSE and that early combination therapies may provide improved outcome over benzodiazepine monotherapy.

Patient empowerment brochures to increase gabapentinoid deprescribing: protocol for the prospective, controlled before-and-after GABA-WHY trial

BACKGROUND

Off-label use of gabapentinoids is common among patients admitted to hospital medical wards, who are at risk of adverse drug events. In this study, we will assess if educational brochures can increase rates of gabapentinoid deprescription among medical inpatients, compared with usual care.

METHODS

We describe the protocol for a prospective before-and-after trial that will take place on 5 medical wards of 2 tertiary care hospitals in Montréal, Canada. The study intervention will include distribution of educational brochures to users of gabapentinoids during hospital admission, as well as short educational sessions for medical staff on safe gabapentinoid prescribing practices. We will include patients with a gabapentinoid prescription before admission who are aged 60 years or older. Exclusion criteria are known seizure disorder, severe cognitive impairment, expected prognosis less than 3 months and inability to read English or French. The primary outcome is the rate of gabapentinoid deprescription at 8 weeks postdischarge. We aim to recruit 160 participants, with a 1:1 distribution between intervention and control groups.

INTERPRETATION

If successful, the use of educational brochures and staff education represents a scalable intervention to reduce gabapentinoid overuse by encouraging deprescription conversations between patients and their health care providers. Results of the study will be disseminated through publication in peer-reviewed journals and presentations at conferences.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT04855578.

Efficacy and Safety of Pregabalin for Muscle Cramps in Liver Cirrhosis: A Double-Blind Randomized Controlled Trial

BACKGROUND

Muscle cramp is possibly related to peripheral nerve hyperexcitability (PNH), and one of the most debilitating symptoms frequently encountered in patients with liver cirrhosis. We investigated whether pregabalin, a gamma-aminobutyric acid analogue, can suppress neuronal excitability and reduce muscle cramps in cirrhotic patients.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial in which study participants with cirrhosis from a single tertiary center were enrolled. Primary endpoint was the relative change in cramp frequency from the run-in to standard dose treatment phase (4 weeks per each). Secondary endpoints included the responder rate, and the changes in cramp frequency during sleep, pain intensity, health-related quality of life (Liver Disease Quality of Life Instrument, Short Form-36) and electrophysiological measures of PNH.

RESULTS

This study was terminated early because of insufficient accrual. 80% (n = 56) of the target number of participants (n = 70) were randomized to pregabalin (n = 29) or placebo (n = 27). Median baseline frequency of muscle cramps (interquartile range) was 5.8 (3.5-10) per week in the pregabalin group and 6.5 (4.0-10) in the placebo group (P = 0.970). The primary analysis showed a significant reduction in cramp frequency with pregabalin compared to placebo (-36% vs. 4.5% for the percentage change, P = 0.010). Secondary outcomes did not differ significantly between the two groups. Adverse effects with pregabalin were mainly dizziness and lethargy.

CONCLUSION

With multiple problems emerging from premature termination in mind, the results suggested an acceptable safety profile and favorable effect of pregabalin in reducing muscle cramps compared to placebo in cirrhotic patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01271660.

Pruritus in dialysis patients. Review and new perspectives

Uremic pruritus (UP) is one of the most uncomfortable symptoms for patients in dialysis. UP has a great impact on dialysis patients' quality of life and has a great prevalence between those (28-70%). Physiopathology of UP is unknown and usually is unnoticed for most nephrologists (in more than 65% of centers is underdiagnosed). This lack of awareness drives to the unsuccessful treatment of this symptom. Moreover, the fact that most studies have been carried out on small populations and the difficulty assessing UP complicates a correct therapeutical approach. For this reason, we have designed treatment algorithms based on the efficacy of the drugs but also its safeness to avoid adverse effects.

Is gabapentin a safe and effective treatment for nonneuropathic pain?

ABSTRACT

A review of the recent literature found that compared with placebo or other pain medications, gabapentin did not significantly reduce nonneuropathic pain. The drug also is associated with an increased risk of adverse reactions, including somnolence, dizziness, and nausea. Given the lack of efficacy and risk of adverse reactions, gabapentin should not be used for nonneuropathic pain.

[Hepatotoxicity probably associated with gabapentin]

BACKGROUND

Gabapentin is an anticonvulsant medication used as an adjuvant in the treatment of neuropathic pain; few cases have been reported in which it causes acute liver injury.

CLINICAL CASE

56-year-old male patient with a history of chronic kidney disease on hemodialysis and narrowing of the spinal canal under treatment with gabapentin, who presented acute liver injury probably secondary to a dose of gabapentin; however, it remitted with the suspension of said drug.

CONCLUSION

Gabapentin lacks liver metabolism; the mechanism by which it produces liver injury is still unknown; however, there are reports of hepatotoxicity associated with its administration, so its use must be individualized for each patient.

Role of astrocytic GABAergic system on inflammatory cytokine-induced anxiety-like behavior

Recent studies have shown that not only neurons but astrocytes contain a considerable amount of γ-aminobutyric acid (GABA), which can be released and activate the receptors responsive to GABA. The purpose of this study is to test whether gliotransmitters from astrocytes may play a role in etiology of anxiety symptoms. Intracerebroventricular (i.c.v.) infusion of interleukin-1β (IL-1β), one of potent inflammatory cytokines, induced anxiety-like behaviors and activated the glial fibrillary acidic protein (GFAP) in the paraventricular nucleus (PVN) of the hypothalamus. Pretreatment with astrocytes toxin, l-α-aminoadipate (L-AAA) reduced anxiety-like behaviors and the GFAP expression in the PVN. Intraparaventricular nucleus (iPVN) infusion of IL-1β produced markedly anxiety-like behaviors and increased release of GABA from astrocytes. However, treatment of glial cell inhibitor, L-AAA or blocker of Bestrophin-1 (Best1), 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) markedly inactivated astrocytes and also reduced the anxiety-like behaviors. Treatment of L-AAA or NPPB decreased IL-1β-induced gliotransmitter GABA release measured by in vivo microdialysis. These results suggest that selective inhibition of astrocytes or astocytic GABA release in the PVN may serve as an effective therapeutic strategy for treating anxiety and affective disorders.

Acute phenibut withdrawal: A comprehensive literature review and illustrative case report

Phenibut is a glutamic acid derivative with activity on the γ-aminobutyric acid (GABA)B, A, and B-phenethylamine receptors. It is prescribed in former Communist Bloc countries for anxiolysis and related psychiatric disorders. It can be easily obtained in Western countries and is thought to have abuse potential. Abrupt discontinuation has been reported to precipitate an abstinence syndrome. A review of the literature identified 22 reported cases, many of which were notable for severe psychomotor agitation and requirements for aggressive pharmacologic treatment. Neurologic and autonomic signs and symptoms may mimic serotonin or neuroleptic malignant syndrome. Patients were typically younger and had coexisting substance abuse disorders to other drugs. Also presented is a case of a 23-year-old male with an acute phenibut abstinence syndrome. This patient exhibited severe psychomotor agitation requiring physical restraints, dexmedetomidine, lorazepam, haloperidol, diphenhydramine, cyproheptadine, melatonin, olanzapine, and baclofen for symptom control.

Hypothyroidism induced by phenytoin and gabapentin: A Case Report

RATIONALE

Antiepileptic drugs (AEDs) are one of the causative drugs of drug-induced hypothyroidism. In most cases, AED-induced hypothyroidism is subclinical and indicated only by abnormalities of free thyroxine (T4) and/or thyroid-stimulating hormone (TSH) levels. Severe symptomatic hypothyroidism following AEDs is rarely reported in the literature.

PATIENT CONCERNS

A 75-year-old man experienced neurologic symptoms including memory impairment, ataxic gait, sensory polyneuropathy and myopathy, lethargy, and edema of the face and lower extremities. He had been administered phenytoin and gabapentin for the treatment of symptomatic traumatic epilepsy 8 years before.

DIAGNOSES

The patient had low free T4 (0.21 ng/dL) and high TSH (113.2 μIU/mL), which indicated hypothyroidism. Negative thyroid-related autoantibody tests and the lack of goiter excluded the possibility of Hashimoto disease. Phenytoin and/or gabapentin were strongly suspected as causing his hypothyroidism.

INTERVENTION

The patient was treated with replacement therapy (levothyroxine 25 μg/day).

OUTCOMES

His symptoms markedly and promptly improved alongside continued antiepileptic therapy.

LESSONS

In this case, the patient's hypothyroidism was assumed to result from different mechanisms of the 2 AEDs leading to thyroid hormone reduction. AEDs can not only cause asymptomatic thyroid hormone abnormalities but also clinically observable hypothyroidism. Therefore, clinicians should be aware of the association between anticonvulsants and symptomatic hypothyroidism.

Gabapentin-Induced Bullous Pemphigoid

Bullous pemphigoid is an autoimmune blistering dermatosis with separation of the epidermis from the dermis. This disease process is common among elderly patients and manifests with subepidermal vesicles and tense bullae. Patients with bullous pemphigoid are more likely to have also received a previous diagnosis of a neurologic disorder. Gabapentin is an antiepileptic that is used to manage neuropathic pain. The authors describe, to their knowledge, the first report of gabapentin-induced bullous pemphigoid in an elderly man with no history of rashes or reactions to other medications.

Gabapentin dose and the 30-day risk of altered mental status in older adults: A retrospective population-based study

Gabapentin is an effective treatment for chronic neuropathic pain but may cause dizziness, drowsiness, and confusion in some older adults. The goal of this study was to assess the association between gabapentin dosing and adverse outcomes by obtaining estimates of the 30-day risk of hospitalization with altered mental status and mortality in older adults (mean age 76 years) in Ontario, Canada initiated on high dose (>600 mg/day; n = 34,159) compared to low dose (≤600 mg/day; n = 76,025) oral gabapentin in routine outpatient care. A population-based, retrospective cohort study assessing new gabapentin use between 2002 to 2014 was conducted. The primary outcome was 30-day hospitalization with an urgent head computed tomography (CT) scan in the absence of evidence of stroke (a proxy for altered mental status). The secondary outcome was 30-day all-cause mortality. The baseline characteristics measured in the two dose groups were similar. Initiation of a high versus low dose of gabapentin was associated with a higher risk of hospitalization with head CT scan (1.27% vs. 1.06%, absolute risk difference 0.21%, adjusted relative risk 1.29 [95% CI 1.14 to 1.46], number needed to treat 477) but not a statistically significant higher risk of mortality (1.25% vs. 1.16%, absolute risk difference of 0.09%, adjusted relative risk of 1.01 [95% CI 0.89 to 1.14]). Overall, the risk of being hospitalized with altered mental status after initiating gabapentin remains low, but may be reduced through the judicious use of gabapentin, use of the lowest dose to control pain, and vigilance for early signs of altered mental status.

Gabapentin for Chronic Neuropathic Pain

CLINICAL QUESTION

Is gabapentin associated with pain relief in people with chronic neuropathic pain?

BOTTOM LINE

Oral gabapentin (1200-3600 mg/d for 4-12 weeks) for patients with moderate or severe neuropathic pain from postherpetic neuralgia (PHN) or painful diabetic neuropathy (PDN) is associated with pain reduction of at least 50% in 14% to 17% more patients than placebo.

Flow cytometric examination of apoptotic effect on brain tissue in postnatal period created by intrauterine oxcarbazepine and gabapentin exposure

OBJECTIVE

For epileptics, pregnancy contains the balance between no seizure period and antiepileptic use having the least teratogenicity risk. The purpose is to analyse with flow cytometry the apoptotic effects on postnatal brain tissue caused by prenatal use of second generation antiepileptics oxcarbazepine (OXC) and gabapentin (GBP) having different effect mechanisms.

METHOD

30 (n = 5 each group) Wistar albino male rats (45-days-old) are used. First 3 groups are exposed to OXC (100 mg/kg/day), GBP (50 mg/kg/day), and saline, respectively on the 1st-5th prenatal days (preimplantation-implantation period) while the second 3 groups are exposed to the same substances on the 6th-15th prenatal days (organogenesis), respectively. After sacrifice, brain tissue samples were made into suspension with mechanic and enzymatic digestion and examined with flow cytometry.

RESULTS

While apoptosis rate appeared high in rats exposed to OXC on the 1st-5th (p < 0.001) and 6th-15th days (p < 0.001), no significant difference occurred for GBP (p = 0.004; p = 0.012) and saline (p = 0.012). Considering time effect in three treatment groups, while difference was not significant for PSS and GBP groups (p = 0.847 and p = 0.934), apoptosis rate was significantly high for OXC on the 6th-15th days compared to the 1st-5th days (p < 0.001).

CONCLUSION

It is observed that the use of OXC causes neurotoxicity during preimplantation, implantation and, especially, organogenesis period (neurogenesis) whereas GBP does not (Fig. 3, Ref. 32).