Emergent Complications of the Newer Anticonvulsants

An update on pharmacotherapy for trigeminal neuralgia

INTRODUCTION

Trigeminal neuralgia is a rare condition that can be effectively treated by carbamazepine or oxcarbazepine but these older drugs are associated with dose-dependent and potentially treatment-limiting adverse effects. Third-generation anticonvulsants, new calcitonin gene-related peptide blockers for migraine, and older drugs such as ketamine and cannabinoids may be promising adjuvants or monotherapeutic options.

AREAS COVERED

The new drugs, their presumed mechanisms of action, safety and efficacy are discussed herein. There is a paucity of robust clinical evidence in support of these drugs for trigeminal neuralgia. New migraine agents are considered as well although migraines and trigeminal neuralgia are distinct, albeit similar, conditions. No new drugs have been released to market in recent years with the specific indication of trigeminal neuralgia.

EXPERT OPINION

In real-world clinical practice, about half of trigeminal neuralgia patients take more than one agent for prevention and combination therapy may be the optimal approach. Combination therapy might allow for lower doses of carbamazepine or oxcarbazepine, thus reducing the number and severity of potential adverse events but the potential for pharmacokinetic drug-drug interactions must be considered. Drug therapy for trigeminal neuralgia involves acute or abortive treatments, often administered in hospital versus long-term preventive therapy, usually involving oral agents.

Topiramate intoxications & hemodialysis - Literature review and the first case report of a massive suicidal intoxication treated with hemodialysis

Background

Topiramate is an anticonvulsant from sulfamate-substituted monosaccharides that is increasingly used to treat migraines. Serious topiramate intoxications have been described. Unfortunately, indications for and the effect of interventions, including hemodialysis, in severe intoxications seem expert-based and lack empirical evidence. We aim to review the literature on topiramate intoxication cases and to describe the first topiramate intoxication with toxicokinetic data following treatment with hemodialysis.

Methods

A literature review was conducted using the PubMed database. Included articles were reviewed for symptoms; management, including acute hemodialysis; toxicokinetic data; and outcomes.

Results

We found 61 hits in the PubMed database and checked 392 references in the snowball search; 22 were included for data extraction, reporting 29 cases. The majority of the patients were female (n = 23/29, 79%), ranging in age from 2 to 44 years (median 21). The ingested topiramate amount ranged from 175 to 40,000 mg (usual maintenance dose of 50 mg BID and a general maximum of 500 mg BID). Topiramate concentrations were reported in eight cases, ranging from 3.7 to 356.6 mg/L (for reference, the therapeutic range is 2-30 mg/L). Serious topiramate intoxications can result in seizures, coma, hemodynamic instability and severe metabolic acidosis. In no single case was hemodialysis used.

Conclusion

Serious symptoms of topiramate intoxications exist, and hemodialysis is used infrequently. If symptoms are refractory to symptomatic treatment, hemodialysis can reduce topiramate concentrations and symptomatology.

Preoperative Management of Medications for Neurologic Diseases: Society for Perioperative Assessment and Quality Improvement Consensus Statement

Neurologic diseases are prevalent in patients undergoing invasive procedures; yet, no societal guidelines exist as to best practice in management of perioperative medications prescribed to treat these disorders. The Society for Perioperative Assessment and Quality Improvement tasked experts in internal medicine, anesthesiology, perioperative medicine, and neurology to provide evidence-based recommendations for preoperative management of these medications. The aim of this review is not only to provide consensus recommendations for preoperative management of patients on medications for neurologic disorders, but also to serve as an educational guide to perioperative clinicians. While, in general, medications for neurologic disorders should be continued preoperatively, an individualized approach may be needed in certain situations (eg, holding anticonvulsants on day of surgery if electroencephalographic mapping is planned during epilepsy surgery). Pertinent interactions with commonly used drugs in anesthesia practice, as well as considerations for targeted laboratory testing or perioperative drug substitutions, are addressed as well.

Normal anion gap metabolic acidosis secondary to topiramate intake: case report

Introducción. El topiramato es un medicamento que se usa en el tratamiento de varios tipos de epilepsia y como profilaxis en casos de cefalea migrañosa. Entre sus mecanismos de acción, la inhibición de la anhidrasa carbónica en el riñón desencadena la excreción de orina alcalina ocasionando acidosis metabólica. Presentación del caso. Paciente femenino de 17 años procedente de la Ciudad de México con antecedente de consumo de topiramato, quetiapina y sertralina para manejo de síndrome depresivo, quien desarrolla acidosis metabólica de anión restante normal secundaria a ingesta de topiramato. La joven requiere soporte ventilatorio invasivo por deterioro del estado de conciencia y síndrome de dificultad respiratoria y presenta adecuada respuesta a manejo con catártico y bicarbonato sin compromiso renal y sin secuelas neurológicas. Discusión. La acidosis metabólica es la alteración ácido base más frecuente en la práctica clínica. La diferencia entre cationes y aniones medibles, conocida como anión restante o brecha aniónica, permite clasificar este tipo de acidosis. Las pérdidas de bicarbonato o trastornos de la función tubular renal generan acidosis de anión restante normal; por el contrario, la acidosis causada por sobreproducción de ácido endógeno o por insuficiencia renal genera anión restante elevado. El topiramato es una causa poco conocida de acidosis metabólica con anión restante normal; al inhibir la anhidrasa carbónica, se ocasiona una acidosis tubular renal mixta o tipo 3 debido a una incapacidad de secreción de hidrogeniones en el túbulo colector y una limitación en la reabsorción del bicarbonato en el túbulo proximal. Conclusión. El topiramato en dosis terapéutica o en sobredosis puede generar acidosis metabólica de anión restante normal debido a la inhibición de la anhidrasa carbónica a nivel renal. Se trata de un cuadro reversible en el cual el manejo con bicarbonato ha mostrado buenos resultados clínicos.

Massive lamotrigine poisoning. A case report

Lamotrigine (LTG) represents the most commonly prescribed of the so-called new generation antiepileptic drugs. We describe a child who was admitted to the emergency room because of generalized tonic-clonic status epilepticus followed by a complex neurological picture with hyperkinesia and acute ataxia as a result of a LTG intoxication. The experience on acute LTG intoxication is very limited in pediatrics. The present case provides information on the clinical picture related to LTG overdose and confirms that drug intoxications should be considered in the differential diagnosis strategy when severe and polymorphic neurological symptoms occur acutely.

Levetiracetam-induced eosinophilic pneumonia

Levetiracetam is widely regarded as a benign antiepileptic drug, compared to older antiepileptic medication. We report a case of eosinophilic pneumonia due to levetiracetam use in a non-smoking woman aged 59 years with no previous respiratory history. Our patient presented with exertional breathlessness and marked desaturation on exertion. She displayed 'reverse bat-wing' infiltrates on her chest radiograph and peripheral eosinophilia on a complete blood count. Her symptoms, radiology and peripheral eosinophilia resolved completely with cessation of levetiracetam and a course of prednisolone. This is the first report of isolated eosinophilic pneumonia due to levetiracetam. Other reports of levetiracetam-induced eosinophilia describe drug rash, eosinophilia and systemic symptoms (DRESS syndrome). Detection of pulmonary drug reactions requires a careful drug history and high index of suspicion. Identifying and reporting a causative agent is crucially important, as cessation of the drug is essential for resolution of the syndrome.

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.

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.

Levetiracetam-induced rage and suicidality: Two case reports and review of literature

Background

Levetiracetam-induced rage is a rare neurobehavioral adverse effect of levetiracetam that is characterized by seething rage, uncontrollable anger, fits of fury, depression, violence, and suicidal tendencies. It occurs more in patients with prior mood or psychotic disturbances. No such case has been reported in Nigeria.

Method

We report two cases of levetiracetam-induced rage. The first patient was a 29-year-old male with a 14-year history of intractable posttraumatic epilepsy. He was initially placed on sodium valproate and phenobarbitone and later had phenobarbitone replaced with levetiracetam. Within the first week of initiating levetiracetam, he became aggressive, bursted into fits of fury, and attacked his siblings. Levetiracetam was stopped, and the seething rage ceased only to reappear when it was reintroduced; hence, the complete withdrawal of levetiracetam. Naranjo probability score for adverse drug reaction was 8.

Results

The second patient was a 23-year-old lady who developed seething rage and made several attempts to kill herself with a knife following addition of levetiracetam to the clonazepam and carbamazepine that she was taking for treatment-resistant epilepsy. Withdrawal and reintroduction of levetiracetam by the relatives led to cessation and reemergence, respectively, of the rage and suicidal tendencies. Naranjo score was 8. Levetiracetam was discontinued.

Conclusion

Neuropsychiatric evaluation for prior mood or psychiatric disorders in those initiating levetiracetam therapy is suggested alongside monitoring for early features of levetiracetam-induced rage by both caregivers and physicians. This will help stem the morbidity and potential mortality associated with this life-threatening adverse drug reaction.

Antiepileptic drug prescribing patterns in Iraq and Afghanistan war veterans with epilepsy

OBJECTIVE

We examined patterns of antiepileptic drug (AED) use in a cohort of Iraq/Afghanistan war veterans (IAVs) who were previously identified as having epilepsy. We hypothesized that clinicians would be more likely to prescribe newer AEDs and would select specific AEDs to treat seizures based on patient characteristics including gender and comorbidities.

METHODS

From the cohort of IAVs previously identified with epilepsy between fiscal years 2009 and 2010, we selected those who received AEDs from the Veterans Health Administration in FY2010. Regimens were classified as monotherapy or polytherapy, and specific AED use was examine overall and by gender. Multivariable logistic regression examined associations of age; gender; race/ethnicity; medical, psychiatric, and neurological comorbidities; and receipt of neurology specialty care associated with the six most commonly used AEDs.

RESULTS

Among 256,284 IAVs, 2123 met inclusion criteria (mean age: 33years; 89% men). Seventy-two percent (n=1526) received monotherapy, most commonly valproate (N=425) and levetiracetam (n=347). Sixty-one percent of those on monotherapy received a newer AED (levetiracetam, topiramate, lamotrigine, zonisamide, oxcarbazepine). Although fewer women than men received valproate, nearly 90% (N=45) were of reproductive age (≤45years). Antiepileptic drug prescribing patterns were associated with posttraumatic stress disorder, bipolar disorder, cerebrovascular disease, dementia/cognitive impairment, headache, and receipt of neurological specialty care (all p<0.01).

SIGNIFICANCE

In this cohort of veterans with epilepsy, most received AED monotherapy and newer AEDs. Prescribing patterns were different for men and women. The patterns observed between AEDs and neurological/psychiatric comorbidities suggest that clinicians are practicing rational prescribing.

A review on antiepileptic drugs-dependent fatigue: pathophysiological mechanisms and incidence

Fatigue represents a common side effect of several drugs, however, the underlying mechanisms have not been well identified. A depression of the central nervous system (CNS) and/or changes in peripheral processes have been associated with the development of fatigue. Antiepileptic drugs (AEDs), generally decreasing CNS excitability, are used in the treatment of seizures as well as other neurological and psychiatric diseases. Fatigue is certainly a common AEDs' side effect, although a high degree of variability exists depending on both patients' characteristics and the drug used. Here, we delineate the pathophysiological central and peripheral mechanisms by which AEDs may cause fatigue also reviewing the available clinical data in order to assess a possible AEDs rank and highlight each AEDs related risk. It appears that drugs acting on the GABAergic system have the highest incidence (with tiagabine exception) of fatigue followed by Gabapentin and Levetiracetam whereas drugs mainly inhibiting sodium channels (Carbamazepine, Eslicarbazepine, Lamotrigine, Phenytoin and Valproate) have the lowest. However, the dose used, AEDs related side effects and patients' characteristics might influence the degree of fatigue observed.

Postmortem levetiracetam (Keppra®) data from North Carolina

Levetiracetam (Keppra®) is one of the newer anticonvulsant drugs used to treat seizures. Since 2003, the North Carolina Office of the Chief Medical Examiner Toxicology Laboratory has collected quantitative levetiracetam data in samples for 56 postmortem cases. The data presented herein will provide the forensic community with concentrations to assist in the interpretation of levetiracetam in postmortem blood. Decedents were divided into two groups according to manner of death as determined by the medical examiner for the purposes of studying levetiracetam concentrations. There were equal numbers of natural (N = 28) and non-natural deaths (N = 28). These data were subsequently divided into subgroups for further study to explore the therapeutic range of levetiracetam and how it relates to postmortem data. The cases not certified as natural were investigated to study levetiracetam concentrations in cases where it was determined to contribute to the cause of death (attributed) and those where it was not (unattributed). Until now, the literature has only reported levetiracetam overdoses in which the individuals have recovered with respiratory support. Discussed are two suicidal drug deaths from 2010 that are noted to have elevated levels of levetiracetam, 190 and 35 mg/L. Also included in the complete data set are postmortem concentrations for five patients under the age of 10 with levetiracetam ranging from 1.4 to 50 mg/L. This paper will also address the adverse effects of the drug and explore its potential risk for suicide.

Effects of pregabalin on smoking behavior, withdrawal symptoms, and cognitive performance in smokers

RATIONALE

In preclinical and clinical studies, medications enhancing the GABA neurotransmission attenuate nicotine reward. Pregabalin, a GABA analogue, presumably interacts with brain glutamate and GABA neurotransmission. The goal of this study was to determine pregabalin's effects on smoking behavior, nicotine withdrawal, craving for cigarettes, and cognitive performance.

METHODS

Twenty-four smokers participated in an outpatient double-blind, placebo-controlled, crossover study. Subjects had a 4-day treatment period with either pregabalin (300 mg/day) or placebo and following a washout period were then crossed over for 4 days to the other treatment. In each treatment period, starting at midnight of day 1, participants were asked to stop smoking until the experimental session on day 4. During the experimental session measures of ad lib smoking behavior, tobacco withdrawal, craving for cigarettes, and cognitive performance were obtained.

RESULTS

Pregabalin treatment, compared to placebo, did not reduce the smoking behavior during the first 3 days of treatment or during ad lib smoking period. Pregabalin treatment attenuated some tobacco withdrawal symptoms including ratings of anxious, irritable, and frustrated in abstinent smokers. Pregabalin treatment also attenuated the subjective ratings of "liking" in response to smoking. Under pregabalin treatment, smokers made more errors in a sustained attention task.

CONCLUSIONS

These findings provide limited support for pregabalin as a treatment for nicotine addiction.

Abnormalities in thalamic neurophysiology in schizophrenia: could psychosis be a result of potassium channel dysfunction?

Psychosis in schizophrenia is associated with source-monitoring deficits whereby self-initiated behaviors become attributed to outside sources. One of the proposed functions of the thalamus is to adjust sensory responsiveness in accordance with the behavioral contextual cues. The thalamus is markedly affected in schizophrenia, and thalamic dysfunction may here result in reduced ability to adjust sensory responsiveness to ongoing behavior. One of the ways in which the thalamus accomplishes the adjustment of sensory processing is by a neurophysiological shift to post-inhibitory burst firing mode prior to and during certain exploratory actions. Reduced amount of thalamic burst firing may result from increased neuronal excitability secondary to a reported potassium channel dysfunction in schizophrenia. Pharmacological agents that reduce the excitability of thalamic cells and thereby promote burst firing by and large tend to have antipsychotic effects.

Complete heart block and death following lamotrigine overdose

CONTEXT. Lamotrigine is used for both seizure and psychiatric disorders. Overdoses typically follow a benign course. CASE DETAILS. A 19-year-old male with bipolar disorder ingested 4  g of lamotrigine. The patient suffered from multiple seizures, charcoal aspiration, respiratory arrest, prolongation of the QRS interval on electrocardiogram, complete heart block, multiorgan failure and ultimately death. DISCUSSION. We describe the emergency department (ED) and ICU course for this patient and briefly review the toxic effects of lamotrigine and the pharmacokinetics with and without hemodialysis.

Moderate toxic effects following acute zonisamide overdose

Zonisamide is an antiepileptic drug that acts on voltage-sensitive sodium and calcium channels, with a modulatory effect on GABA-mediated neuronal inhibition and an inhibitory effect on carbonic anhydrase. It is used mainly for the treatment of partial seizures, and is generally well tolerated at therapeutic doses. The most common reported adverse effects are somnolence, anorexia, dizziness, and headache. There are limited data on zonisamide overdose in the literature, and no case of zonisamide mono-intoxication has been published to date. We describe the first case of zonisamide mono-intoxication in a 25-year-old woman who ingested 12.6 g of this substance with suicidal intent. Despite a plasma zonisamide concentration of 182 mg/L on admission, the patient exhibited a benign clinical course with vomiting and central nervous system depression, requiring brief intubation. Somnolence persisted for 50 hours, and normal-anion-gap metabolic acidosis and polyuria for several days. Complete recovery may be expected with supportive care, even after ingestion of large zonisamide overdoses.