Gabapentin-induced Myoclonus in End-stage Renal Disease

Iatrogenic Epileptogenicity Caused by CNS Drugs: A Short Case Series and Narrative Review

Multiple medications are known to increase epileptogenicity in patients with and without an underlying seizure disorder. Paradoxically, some of these medications include anti-seizure medications (ASMs) and other medications, such as psychotropics, that act on the central nervous system (CNS). This article aims to discuss 3 clinical cases that highlight the gamut of epileptogenic reactivity secondary to CNS drugs ranging from increased epileptogenicity in the form of interictal epileptiform discharges (IEDs) without seizures, increased epileptogenicity on electroencephalogram (EEG) with associated non-epileptic movement disorders, and frank, de novo seizures. We also analyze the relevant literature on the impact of CNS medications on epileptogenicity.

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).

Negative myoclonus induced by gabapentin and pregabalin: A case series and systematic literature review

INTRODUCTION

Negative myoclonus is a jerky, brief, and sudden interruption of voluntary muscle contraction. Although gabapentin and pregabalin have been reported to induce positive myoclonus in some patients with impaired renal function, there are only a few studies describing pregabalin- or gabapentin-induced negative myoclonus. This study reviewed patients who had developed pregabalin- or gabapentin-induced negative myoclonus.

METHODS

We collected the patients with negative myoclonus who were referred to the department of neurology at a university-affiliated hospital and selected pregabalin- or gabapentin-induced negative myoclonus. Then reviewed the literature with respect to pregabalin- or gabapentin-induced negative myoclonus.

RESULTS

A total of 77 patients with negative myoclonus were reviewed. Among them, 21 neuropathic pain patients who were prescribed and developed negative myoclonus induced by pregabalin (9 cases) or gabapentin (12 cases). To prove causality of the drug, probable and certain level of category according to the WHO-UMC criteria were recruited. Of the 21 patients, 3 had impaired renal function, while 18 had normal renal function. Review of the literature identified 7 further cases (6 had normal renal function) with pregabalin- or gabapentin-induced negative myoclonus.

CONCLUSION

Pregabalin- and gabapentin-induced negative myoclonus can develop even in patients with normal renal function. Physicians should keep in mind the possibility of patients developing negative myoclonus under treatment of pregabalin or gabapentin even in short period of time and with low dosage, and in the normal range of renal function. Further prospective study investigating incidence and risk factors is warranted.

The clinical heterogeneity of drug-induced myoclonus: an illustrated review

A wide variety of drugs can cause myoclonus. To illustrate this, we first discuss two personally observed cases, one presenting with generalized, but facial-predominant, myoclonus that was induced by amantadine; and the other presenting with propriospinal myoclonus triggered by an antibiotic. We then review the literature on drugs that may cause myoclonus, extracting the corresponding clinical phenotype and suggested underlying pathophysiology. The most frequently reported classes of drugs causing myoclonus include opiates, antidepressants, antipsychotics, and antibiotics. The distribution of myoclonus ranges from focal to generalized, even amongst patients using the same drug, which suggests various neuro-anatomical generators. Possible underlying pathophysiological alterations involve serotonin, dopamine, GABA, and glutamate-related processes at various levels of the neuraxis. The high number of cases of drug-induced myoclonus, together with their reported heterogeneous clinical characteristics, underscores the importance of considering drugs as a possible cause of myoclonus, regardless of its clinical characteristics.

Myoclonus in renal failure: Two cases of gabapentin toxicity

Gabapentin, an AED approved for the adjunctive treatment of partial seizures with/without secondary generalization and for the treatment of postherpetic neuralgia, is frequently used off-label for the treatment of both psychiatric and pain disorders. Since gabapentin is cleared solely by renal excretion, dosing requires consideration of the patient's renal function. Myoclonic activity may occur as a complication of gabapentin toxicity, especially with acute kidney injury or end-stage renal disease. We report 2 cases of myoclonic activity associated with gabapentin toxicity in the setting of renal disease which resolved with discontinuation of gabapentin and treatment with hemodialysis and peritoneal dialysis. As gabapentin has multiple indications and off-label uses, an understanding of myoclonus, neurotoxicity, and renal dosing is important to clinicians in multiple specialties.

Treatment of gabapentin-induced myoclonus with continuous renal replacement therapy

A 56-year-old man with diabetes, hypertension, and chronic kidney disease presented to the emergency room with a complaint of pain in his right foot. He was found to have tremors. Gabapentin toxicity was suspected and the patient was found to have high gabapentin level (6.3 mcg/ml). Patient was commenced on continuous venovenous hemodiafiltration (CVVHD) and the pharmacokinetics of gabapentin was studied. The patient improved symptomatically and his tremors subsided. In this case report, we describe the successful management of gabapentin toxicity with continuous renal replacement therapy and calculate the clearance of gabapentin which will enable future treatment of gabapentin toxicity by CVVHD.

Review of therapeutic options for adjuvant treatment of focal seizures in epilepsy: focus on lacosamide

Epilepsy is one of the most common serious neurological conditions worldwide, with an age-adjusted incidence of approximately 50 per 100,000 persons per year in developed countries. Antiepileptic therapy can result in long-term remission in 60-70% of patients, but many patients will require combination treatment to achieve optimal seizure control, as monotherapy is ineffective at controlling seizures in 30-53% of patients. Despite the increase in available treatment options, patient outcomes have not improved significantly and there is still a need for more effective therapies. Drugs used in the treatment of focal-onset seizures are a diverse range of compounds, and in most cases their mechanism of action is unknown or poorly defined. This review discusses the efficacy and safety of the newer adjuvant antiepileptic therapies that may improve outcomes in patients unresponsive to monotherapy, including clobazam, vigabatrin, lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam, oxcarbazepine, pregabalin, zonisamide and eslicarbazepine, with focus on lacosamide. Lacosamide has been shown to exert its anticonvulsant effects predominantly by enhancement of the slow inactivation of voltage-gated sodium channels. Lacosamide is indicated for use as adjuvant treatment of focal-onset seizures in patients with epilepsy, and there is some evidence that it may also be of use in patients with status epilepticus and cancer patients with epilepsy. The efficacy of lacosamide has been assessed in three randomized, double-blind, placebo-controlled clinical trials, all of which have shown lacosamide to be effective at reducing seizure frequency and increasing 50% responder rates in patients with focal-onset seizures. Long-term lacosamide treatment is generally well tolerated and is not associated with significant drug interactions; the availability of an intravenous form of the drug also makes it particularly useful for a broad range of patients.

[Epilepsy practice for neurologists]

Epilepsy is a common disease with a high incidence of about one percent. Knowledge of seizure semiology and correct reading of EEG findings are important for diagnosis of epilepsy. Because the primary therapy for epilepsy is antiepileptic drugs (AEDs), including several ones that are newly permitted in Japan, we need to prescribe them based on an understanding of their actions and interaction mechanisms. However, we also need to consider early surgical treatment for temporal lobe epilepsy with hippocampal sclerosis. In the therapeutic decision for adult epilepsy patients many factors such as employment, marriage, child bearing, and co-existent disease need to be considered. The present review provides an overview of the basis of epilepsy practice for neurologists treating adults with epilepsy, including a discussion of new AEDs, epilepsy surgery, women with epilepsy, and epilepsy in the elderly.

Myoclonus

Myoclonus can be classified as physiologic, essential, epileptic, and symptomatic. Animal models of myoclonus include DDT and posthypoxic myoclonus in the rat. 5-Hydrotryptophan, clonazepam, and valproic acid suppress myoclonus induced by posthypoxia. The diagnostic evaluation of myoclonus is complex and involves an extensive work-up including basic electrolytes, glucose, renal and hepatic function tests, paraneoplastic antibodies, drug and toxicology screens, thyroid antibody and function studies, neurophysiology testing, imaging, and tests for malabsorption disorders, assays for enzyme deficiencies, tissue biopsy, copper studies, alpha-fetoprotein, cytogenetic analysis, radiosensitivity DNA synthesis, genetic testing for inherited disorders, and mitochondrial function studies. Treatment of myoclonus is targeted to the underlying disorder. If myoclonus physiology cannot be demonstrated, treatment should be aimed at the common pattern of symptoms. If the diagnosis is not known, treatment could be directed empirically at cortical myoclonus as the most common physiology. In cortical myoclonus, the most effective drugs are sodium valproic acid, clonazepam, levetiracetam, and piracetam. For cortical-subcortical myoclonus, valproic acid is the drug of choice. Here, lamotrigine can be used either alone or in combination with valproic acid. Ethosuximide, levetiracetam, or zonisamide can also be used as adjunct therapy with valproic acid. A ketogenic diet can be considered if everything else fails. Subcortical-nonsegmental myoclonus may respond to clonazepam and deep-brain stimulation. Rituximab, adrenocorticotropic hormone, high-dose dexamethasone pulse, or plasmapheresis have been reported to improve opsoclonus myoclonus syndrome. Reticular reflex myoclonus can be treated with clonazepam, diazepam and 5-hydrotryptophan. For palatal myoclonus, a variety of drugs have been used.

The management of diabetic neuropathy in CKD

A 64-year-old male with a 15-year history of poorly controlled type 2 diabetes and a 10-year history of hypertension and hyperlipidemia had developed multiple diabetes-related complications within the last 5 years. He first developed albuminuria 5 years ago, and over the next several years experienced fairly rapid decline in kidney function, with eGFR of 55 mL/min/1.73m2 noted 2 years ago. He was diagnosed with proliferative retinopathy 5 years ago and underwent laser photocoagulation. Four years ago, he noted symptoms of peripheral neuropathy manifested as shooting pain and numbness with loss of light touch, thermal and vibratory sensation in a stocking distribution. Last year he developed a non-healing ulcer on the plantar aspect of his left foot which was complicated with gangrene and resulted in a below-the-knee amputation of the left leg one year ago. He now reports a new onset of weakness, lightheadedness and dizziness on standing that affects his daily activities. He reports lancinating pain in his right lower extremity, worse in the evening. Medications include: neutral protamine Hagedorn insulin twice daily and regular insulin on a sliding scale, metoprolol 50 mg/d, lisinopril 40 mg/d, atorvastatin 80 mg/d, furosemide 40 mg/d and aspirin 81 mg/d. Blood pressure is 127/69 mm Hg with a pulse rate of 96 bpm while supine and 94/50 mmHg with a pulse rate of 102 bpm while standing. Strength is normal but with a complete loss of all sensory modalities to the knee in his remaining limb and up to the wrists in both upper extremities, and he is areflexic. Today's laboratory evaluations show a serum creatinine of 2.8 mg/dl, an estimated GFR (eGFR) of 24 ml/min/1.73m2, a hemoglobin A1c (HbA1c) of 7.9 % and 2.1 g of urine protein per gram of creatinine. What would be the most appropriate management for this patient?

[Development or worsening of myoclonus associated with gabapentin therapy]

PURPOSE

To evaluate the development or worsening of myoclonus in patients receiving gabapentin (GBP).

METHODS

Clinical charts of 162 patients treated with GBP were reviewed concerning development or worsening of myoclonus.

RESULTS

We found 3 cases (1.9%) of myoclonus. Two patients had preexisting myoclonus and generalized tonic-clonic seizures, while the other one had generalized tonic-clonic seizures only. All patients experienced development or worsening of myoclonus within 2 weeks after starting GBP. Dose at the onset of development or worsening of myoclonus varied from 600 mg to 1,800 mg. Two patients developed multifocal myoclonus. Discontinuation of GBP or clonazepam add-on resulted in cessation of myoclonus with no serious sequela.

CONCLUSION

GBP may increase the risk of development of de novo myoclonus or worsening of myoclonus in patients with preexistent myoclonus. According to the result of this study and the treatment guidelines, GBP should be avoided when a patient has preexistent myoclonus.

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.

Treating seizures in renal and hepatic failure

INTRODUCTION: Renal and hepatic diseases cause seizures and patients with epilepsy may suffer from such diseases which change antiepileptic drugs (AEDs) metabolism. OBJECTIVES: To revise how seizures may be caused by metabolic disturbances due to renal or hepatic diseases, by their treatment or by comorbidities and how AEDs choice might be influenced by these conditions. RESULTS: Seizures arise in renal failure due to toxins accumulation and to complications like sepsis, hemorrhage, malignant hypertension, pH and hydroelectrolytic disturbances. Hemodialysis leads to acute dysequilibrium syndrome and to dementia. Peritoneal dialysis may cause hyperosmolar non-ketotic coma. Post-renal transplant immunosupression is neurotoxic and cause posterior leukoencephalopathy, cerebral lymphoma and infections. Some antibiotics decrease convulsive thresholds, risking status epilepticus. Most commonly used AEDs in uremia are benzodiazepines, ethosuximide, phenytoin and phenobarbital. When treating epilepsy in renal failure, the choice of AED remains linked to seizure type, but doses should be adjusted especially in the case of hydrosoluble, low-molecular-weight, low-protein-bound, low apparent distribution volume AEDs. Hepatic failure leads to encephalopathy and seizures treated by ammonium levels and intestinal bacterial activity reductions, reversal of cerebral edema and intracranial hypertension. Phenytoin and benzodiazepines are usually ineffective. Seizures caused by post-hepatic immunosupression can be treated by phenytoin or levetiracetam. Seizures in Wilson's disease may result from D-penicillamine dependent piridoxine deficiency. Porphyria seizures may be treated with gabapentin, oxcarbazepine and levetiracetam. Hepatic disease changes AEDs pharmacokinetics and needs doses readjustments. Little liver-metabolized AEDs as gabapentin, oxcarbazepine and levetiracetam are theoretically more adequate. CONCLUSIONS: Efficient seizures treatment in renal and hepatic diseases requires adequate diagnosis of these disturbances and their comorbidities besides good knowledge on AEDs metabolism, their pharmacokinetic changes in such diseases, careful use of concomitant medications and AEDs serum levels monitoring.

Myoclonus induced by the use of gabapentin

Myoclonus is a rare side effect of gabapentin (GBP) and has been reported in patients with preexisting myoclonus, mental retardation, chronic static encephalopathy, diffuse brain damage, impaired renal function, or end stage renal disease. We report a case of myoclonus in a patient with normal renal function and no previous disorders. A 69-year-old female underwent diskectomy and foraminotomy at the left L4-L5 level. Postoperatively, she complained of paresthesia in her left leg, which was thought to be due to root manipulation during surgery. To relieve the paresthesia, she was given tramadol, an oral opioid agonist, and GBP. One week after GBP was increased to 900 mg per day, myoclonus developed, which severely impaired her normal activity. Her symptoms resolved 2 days after discontinuation of GBP. The coadministration of tramadol and GBP may mutually enhance the myoclonic potential of each drug. The causal relationship between GBP and myoclonus was suggested by cessation of myoclonus after GBP discontinuation despite continued therapy with tramadol.

Life-Threatening Status Epilepticus Following Gabapentin Administration in a Patient with Benign Adult Familial Myoclonic Epilepsy

We report the case of a 57-year-old man who experienced life-threatening myoclonic status after the administration of gabapentin. Based on familial data, the patient was determined to be a member of a previously described family with benign adult familial myoclonic epilepsy (BAFME). The myoclonic status did not respond to benzodiazepines, but resolved after discontinuing the gabapentin. As for other idiopathic generalized epilepsies, gabapentin may precipitate myoclonic status in a benign syndrome, such as BAFME, as is reported herein for the first time. A correct diagnosis and prompt discontinuation of the drug may reverse a potentially severe, life-threatening condition.

Safety and efficacy of anticonvulsants in elderly patients with psychiatric disorders: oxcarbazepine, topiramate and gabapentin

Few controlled studies are available to guide the clinician in treating potentially assaultive elderly individuals with psychiatric disorders. Safety concerns limit the use of benzodiazepines and antipsychotic medications in the elderly individual, making anticonvulsants an attractive alternative. This paper reviews three specific anticonvulsants for this purpose: gabapentin, oxcarbazepine and topiramate, describing safety and efficacy in elderly patients with severe agitation from psychosis or dementia. Gabapentin, renally excreted, with a half-life of 6.5-10.5 h, may cause ataxia. Oxcarbazapine, hepatically reduced, may cause hyponatremia, and topiramate may cause significant cognitive impairment. Nonetheless, these are important medications to consider in the treatment of agitation.

Overtreatment in epilepsy: how it occurs and how it can be avoided

In pharmacotherapy, overtreatment may be defined as an excessive drug load (that is, excessive drug dosages or unnecessary polypharmacy) leading to a suboptimal risk-to-benefit ratio. The risk of overtreatment in the pharmacological management of epilepsy is substantial and may have serious consequences in terms of a greater incidence and severity of adverse effects. These effects can range from subtle CNS impairment to overt toxic effects, including teratogenicity. Overtreatment also causes increased treatment costs and may even lead to a paradoxical deterioration in seizure control. The prevention and correction of overtreatment requires a thorough understanding of the situations and mechanisms that lead to inappropriate prescribing of antiepileptic drugs. These include initiating treatment in conditions where it is not indicated (for example, long-term prophylaxis after head trauma or supratentorial surgery in seizure-free patients), use of excessively fast titration rates, prescription of excessively high initial target dosages, failure to consider conditions associated with reduced dosage requirements (for example, old age or comorbidities associated with impaired drug clearance), and failure to consider the dose-response characteristics of the selected drug. Many patients whose seizures do not respond to the initially prescribed medication can be optimally managed by switching to monotherapy with an alternative agent; premature use of combination therapy represents another common form of overtreatment. Overtreatment may also result from a failure to adjust the dosage to prevent or compensate for adverse pharmacokinetic or pharmacodynamic drug interactions, and from a failure to reduce drug load in patients who have not benefited from high dosages or polypharmacy. While the measurement of drug concentrations can aid in minimising adverse effects, there is also a danger of overtreatment resulting from inappropriate interpretation of drug concentration data. Continuation of drug therapy in seizure-free patients in whom the risk-benefit ratio is in favour of gradual withdrawal may also be regarded as overtreatment. Tailoring therapy to the needs of the individual patient is the key to the successful management of epilepsy. Even though the importance of complete seizure control cannot be overemphasised, no patient should be made to suffer more from the adverse effects of treatment than from the manifestations of the seizure disorder.