Valproate-Induced Hyperammonemic Encephalopathy and Normal Liver Functions: Possible Synergism With Topiramate

Valproate-related hyperammonemic encephalopathy with generalized suppression EEG: a case report

BACKGROUND

Valproic acid (VPA) is a prevalent antiseizure medication (ASM) used to treat epilepsy. Valproate-related hyperammonemic encephalopathy (VHE) is a type of encephalopathy that can occur during neurocritical situations. In VHE, the electroencephalogram (EEG) displays diffuse slow waves or periodic waves, and there is no generalized suppression pattern.

CASE PRESENTATION

We present a case of a 29-year-old female with a history of epilepsy who was admitted for convulsive status epilepticus (CSE), which was controlled by intravenous VPA, as well as oral VPA and phenytoin. The patient did not experience further convulsions but instead developed impaired consciousness. Continuous EEG monitoring revealed a generalized suppression pattern, and the patient was unresponsive. The patient's blood ammonia level was significantly elevated at 386.8 μmol/L, indicating VHE. Additionally, the patient's serum VPA level was 58.37 μg/ml (normal range: 50-100 μg/ml). After stopping VPA and phenytoin and transitioning to oxcarbazepine for anti-seizure and symptomatic treatment, the patient's EEG gradually returned to normal, and her consciousness was fully restored.

DISCUSSION

VHE can cause the EEG to display a generalized suppression pattern. It is crucial to recognize this specific situation and not to infer a poor prognosis based on this EEG pattern.

Drug-induced hyperammonaemia

Hyperammonaemia (HA) as a consequence of numerous primary or secondary causes, gives rise to clinical manifestations due to its toxic effects on the brain. The neurological consequences broadly reflect the ammonia level, duration and age, with paediatric patients being more susceptible. Drug-induced HA may arise due to either decreased ammonia elimination or increased production. This is associated most frequently with use of valproate and presents a dilemma between ongoing therapeutic need, toxicity and the possibility of an alternative cause. As there is no specific test for drug-induced HA, prompt discussion with a metabolic physician is recommended, as the neurotoxic effects are time-dependent. Specific guidelines for managing drug-induced HA have yet to be published and hence the treatment approach outlined in this review reflects that outlined in relevant urea cycle disorder guidelines.

Valproic Acid-Associated Hyperammonemia: A Systematic Review

BACKGROUND

Hyperammonemia is an adverse effect that poses clinical uncertainty around valproic acid (VPA) use. The prevalence of symptomatic and asymptomatic hyperammonemia and its relationship to VPA concentration is not well established. There is also no clear guidance regarding its management. This results in variability in the monitoring and treatment of VPA-induced hyperammonemia. To inform clinical practice, this systematic review aims to summarize evidence available around VPA-associated hyperammonemia and its prevalence, clinical outcomes, and management.

METHODS

An electronic search was performed through Ovid MEDLINE, Ovid Embase, Web of Science, and PsycINFO using search terms that identified hyperammonemia in patients receiving VPA. Two reviewers independently performed primary title and abstract screening with a third reviewer resolving conflicting screening results. This process was repeated during the full-text review process.

RESULTS

A total of 240 articles were included. Prevalence of asymptomatic hyperammonemia (5%-73%) was higher than symptomatic hyperammonemia (0.7%-22.2%) and occurred within the therapeutic range of VPA serum concentration. Various risk factors were identified, including concomitant medications, liver injury, and defects in carnitine metabolism. With VPA discontinued, most symptomatic patients returned to baseline mental status with normalized ammonia level. There was insufficient data to support routine monitoring of ammonia level for VPA-associated hyperammonemia.

CONCLUSIONS

Valproic acid-associated hyperammonemia is a common adverse effect that may occur within therapeutic range of VPA. Further studies are required to determine the benefit of routine ammonia level monitoring and to guide the management of VPA-associated hyperammonemia.

A glance at transient hyperammonemia of the newborn: Pathophysiology, diagnosis, and treatment: A review

Hyperammonemia is the excessive accumulation of ammonia in the blood, and is usually defined as a plasma level above 100 µmol/L in neonates or above 50 µmol/L in term infants, children, and adolescents. Patients with hyperammonemia usually experience life-threatening neuropsychiatric symptoms, especially newborns. It is routinely caused by inherited metabolic diseases and also by acquired disorders, such as liver failure, portosystemic shunting, gastrointestinal hemorrhage, ureterosigmoidostomy, renal tubular acidosis, hypoxic ischemic encephalopathy, infections with urea-metabolizing organisms, and some drugs. Transient hyperammonemia of the newborn (THAN) is a special type of hyperammonemia acknowledged in the field of metabolic disease as an inwell-defined or well-understood entity, which can be diagnosed only after the exclusion of genetic and acquired causes of hyperammonemia. Although the prognosis for THAN is good, timely identification and treatment are essential. Currently, THAN is underdiagnosed and much less is mentioned for early diagnosis and vigorous treatment. Herein, we present common themes that emerge from the pathogenesis, diagnosis, and management of THAN, based on current evidence. When a newborn presents with sepsis, intracranial hemorrhage, or asphyxia that cannot explain coma and seizures, doctors should always keep this disease in mind.

Which treatment strategy in patients with epilepsy with focal seizures uncontrolled by the first anti-seizure medication?

There is no definite proven or accepted strategy in the management of patients with focal epilepsy uncontrolled by the first anti-seizure medication (ASM). Clinical studies failed to find a significant difference in efficacy or tolerability between alternative monotherapy and/or adjunctive therapy in these patients. A second ASM is often added, the efficacy of the combination is assessed, and the dose of the first drug can be gradually reduced and withdrawn. If seizures recur, the effective combination therapy can be reinstated. In this review, we discussed experimental and clinical data about the efficacy and tolerability of the most frequently used combinations of ASMs. Animal studies suggested that the most favorable combinations are those between ASMs with different or multiple mechanisms of action, whereas combining drugs with similar pharmacodynamic properties is often associated with additive or infra-additive efficacy and additive or synergistic toxicity. Clinical studies have shown that levetiracetam (LEV) can be favorably combined with the sodium channel blockers (SCBs) lacosamide (LCM) and lamotrigine (LTG). Lamotrigine is particularly effective when associated with valproate (VPA) and possibly with LEV and topiramate (TPM). Carbamazepine (CBZ) has negative pharmacokinetic interactions with several ASMs and should not be combined with other SCBs; it could be effectively and safely combined with gabapentin (GBP) and LEV. Valproic acid has enzyme inhibiting properties and can be cautiously used with SCBs; its combination with TPM or zonisamide (ZNS) may be associated with higher toxicity.

A Mysterious Case of Recurrent Acute Hyperammonemic Encephalopathy

Ammonia is a well-recognized neurotoxin. Awareness about hyperammonemia, in the absence of liver cirrhosis, may help in lifesaving, prompt diagnosis, and treatment. We present a case of a 53-year-old male who presented to the emergency department (ED) with altered mental status (AMS). He was unresponsive with occasional eye opening. Initial labs were normal except for mildly elevated blood alcohol level. Serum ammonia levels were very high (305 umol/L). He improved with lactulose. He had similar admissions later on. Urine orotic acid levels were high confirming ornithine transcarbamylase (OTC) deficiency. Noncirrhotic hyperammonemia as a cause of AMS remains a diagnosis of exclusion requiring high index suspicion. Very few cases of late inborn errors of urea cycle disorders (UCDs) have been reported in the literature. Our case highlights the importance of early diagnosis of UCDs and that outcome can be excellent if treated aggressively. Once identified, adult-onset forms of the UCDs have a good prognosis-largely due to the initiation of preventative measures and earlier recognition of exacerbations.

Noncirrhotic hyperammonemia: A factor behind dementia to alter mental status

Healthcare givers were recommended to check serum ammonia level for elderly patients with acute-on-chronic alteration of mental status. Early initiation of antihyperammonemia therapy may benefit improvement of alteration of mental status. Baseline mental status becomes necessary for diagnose the acute alteration of mental status and monitor the therapeutic process.

Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision

In 2012, we published guidelines summarizing and evaluating late 2011 evidence for diagnosis and therapy of urea cycle disorders (UCDs). With 1:35 000 estimated incidence, UCDs cause hyperammonemia of neonatal (~50%) or late onset that can lead to intellectual disability or death, even while effective therapies do exist. In the 7 years that have elapsed since the first guideline was published, abundant novel information has accumulated, experience on newborn screening for some UCDs has widened, a novel hyperammonemia-causing genetic disorder has been reported, glycerol phenylbutyrate has been introduced as a treatment, and novel promising therapeutic avenues (including gene therapy) have been opened. Several factors including the impact of the first edition of these guidelines (frequently read and quoted) may have increased awareness among health professionals and patient families. However, under-recognition and delayed diagnosis of UCDs still appear widespread. It was therefore necessary to revise the original guidelines to ensure an up-to-date frame of reference for professionals and patients as well as for awareness campaigns. This was accomplished by keeping the original spirit of providing a trans-European consensus based on robust evidence (scored with GRADE methodology), involving professionals on UCDs from nine countries in preparing this consensus. We believe this revised guideline, which has been reviewed by several societies that are involved in the management of UCDs, will have a positive impact on the outcomes of patients by establishing common standards, and spreading and harmonizing good practices. It may also promote the identification of knowledge voids to be filled by future research.

Treating status migrainosus in the emergency setting: what is the best strategy?

INTRODUCTION

Migraine is a disabling primary headache disorder with unknown exact pathomechanism. Status migrainosus (SM) is a complication of migraine (with or without aura), representing an attack that lasts for more than 72 h. There is a paucity of data published with regard to its pathomechanism and therapeutic options.

AREAS COVERED

The authors review the literature on SM from PubMed published between 1999 and January 2018. The authors specifically look at the therapeutic possibilities of SM in the emergency department in patients that have or have not already been treated with serotonergic agents. Additional discussion is given to the rare complications of migraine.

EXPERT OPINION

SM is a devastating condition; therefore, the primary goal is to prevent its development with proper acute and prophylactic migraine medication. If this treatment fails, the patient should be treated in the emergency setting. Due to the severity of the condition, parenteral pharmacotherapy is recommended. However, high-quality randomized trials are lacking. The currently available data suggest the use of intravenous fluids, corticosteroids, magnesium sulfate, anticonvulsive drugs, nonsteroidal anti-inflammatory drugs, antiemetics, and serotonergic agents for the treatment of SM. Still, there is a need for personalized and causal therapy for migraine sufferers.

Gait instability in valproate-treated patients: Call to measure ammonia levels

OBJECTIVE

Hyperammonemia induced by valproate (VPA) treatment may lead to several neurological and systemic symptoms as well as to seizure exacerbation. Gait instability and recurrent falls are rarely mentioned as symptoms, especially not as predominant ones.

METHODS

We report five adult patients with frontal lobe epilepsy (FLE) who were treated with VPA and in whom a primary adverse effect was unstable gait and falls.

RESULTS

There were four males and one female patients with FLE, 25-42-year-old, three following epilepsy surgery. All of them were treated with antiepileptic drug polytherapy. Gait instability with falls was one of the principal sequelae of the treatment. Patients also exhibited mild encephalopathy (all patients) and flapping tremor (three patients) that developed following the addition of VPA (three patients) and with chronic VPA treatment (two patients). VPA levels were within the reference range. Serum ammonia levels were significantly elevated (291-407 μmole/L, normal 20-85) with normal or slightly elevated liver enzymes. VPA dose reduction or discontinuation led to the return of ammonia levels to normal and resolution of the clinical symptoms, including seizures, which disappeared in two patients and either decreased in frequency or became shorter in duration in the other three.

CONCLUSIONS

Gait instability due to hyperammonemia and VPA treatment is probably under-recognized in many patients. It can develop when the VPA levels are within the reference range and with normal or slightly elevated liver enzymes.

Selecting Rational Drug Combinations in Epilepsy

Monotherapy remains the standard initial therapy of epilepsy, but when the first antiepileptic drug (AED) fails, combination therapy may be considered. The choice of combination therapy should take into consideration pharmacokinetic interactions, as well as pharmacodynamic interactions related to mechanism of action. There is evidence that an AED combination with different mechanisms of action is more likely to be successful than a combination with the same mechanisms. The combination of lamotrigine and valproate has been demonstrated to be synergistic in its efficacy. However, there are limited data to support other synergistic AED combinations.

Increased risk of chronic liver disease in patients with bipolar disorder: A population-based study

OBJECTIVE

This study aimed to investigate the prevalence and incidence of chronic liver disease in patients with bipolar disorder.

METHODS

We used a random sample of 766,427 subjects aged ≥18 years from the National Health Research Institute database in the year 2005. Subjects with at least one primary diagnosis of bipolar disorder in 2005 were identified. Patients with a primary or secondary diagnosis of chronic liver disease were also defined. We compared the prevalence and associated factors of chronic liver disease between patients with bipolar disorder and the general population in 2005. We also compared the incidence of chronic liver disease in patients with bipolar disorder and the general population from 2006 to 2010.

RESULTS

The prevalence of chronic liver disease in patients with bipolar disorder (13.9%) was 2.68 times higher than that of the general population (5.8%) in 2005. The average annual incidence of chronic liver disease in patients with bipolar disorder from 2006 to 2010 was also higher than that of the general population (2.95% vs. 1.73%; risk ratio: 1.71; 95% confidence interval: 1.46-2.01).

CONCLUSIONS

Patients with bipolar disorder had a significantly higher prevalence and incidence of chronic liver disease than those in the general population, and younger patients with bipolar disorder have a much higher prevalence and incidence than those in the general population. Male sex, second-generation antipsychotic or antidepressant use, and hyperlipidemia were associated factors for chronic liver disease in patients with bipolar disorder.

Topiramate-Related Hyperammonemia

Objective: To report a case of hyperammonemia associated with the interaction between topiramate and valproic acid. Case Summary: We present a patient case with topiramate-related hyperammonemia. The patient was on topiramate prior to admission and presented with an elevated ammonia level following 2 doses of valproic acid. The increased dosing frequency of valproic acid further exacerbated the hyperammonemia. On discontinuation of topiramate and the tapering of the dose of valproic acid the patient's ammonia level returned to normal. Discussion: Valproic acid-induced hyperammonemic encephalopathy is well documented and there are several proposed mechanisms. The interaction between valproic acid and topiramate causing drug-induced hyperammonemia encephalopathy is documented in several case reports. The interaction is associated with the addition of topiramate to a patient's medication regimen that previously included valproic acid. Topiramate also has several proposed mechanisms for predisposing patients for hyperammonemia. There are limited data on topiramate monotherapy or long-term use of topiramate use causing hyperammonemia-associated encephalopathy or enhancing hyperammonemia with the addition of valproic acid. Conclusions: This case supports topiramate-related hyperammonemia and the pharmacodynamic interaction with the co-administration of valproic acid.

Topiramate-induced hyperammonemic encephalopathy in a patient with mental retardation: A case report and review of the literature

Hyperammonemia is an uncommon side effect of topiramate (TPM) that has only been reported when it is used as an adjunct to valproate. We report a patient with mental retardation who developed reversible encephalopathy from TPM. Ammonia level was monitored during the course of TPM treatment. This patient had recurring, reversible elevations in serum ammonia levels that coincided with the administration of TPM. To our knowledge, symptomatic hyperammonemia has not been reported to occur with TPM monotherapy.

Hyperammonemic Encephalopathy due to Valproic Acid and Topiramate Interaction

Valproic acid-induced hyperammonemic encephalopathy is a rare yet serious adverse drug reaction. Medication interactions such a valproic acid and topiramate can precipitate an event. We present the case of a 52-year-old female that presented with acute mental status change and hypersomnolence due to hyperammonemia caused by a valproic acid derivative. The patient improved after withdrawal of the offending medications and treatment with lactulose. Clinicians should remain hypervigilant in monitoring for valproic acid-induced hyperammonemic encephalopathy and risk factors such as polypharmacy.

Valproate-induced hyperammonemia in juvenile ceroid lipofuscinosis (Batten disease)

PURPOSE

Valproate-induced hyperammonemia (VHA) and hyperammonemic encephalopathy (VHE) are well-known complications of valproate (VPA) treatment. Currently recognised risk factors for VHE include a high VPA dosage, the need for polytherapy and long duration of treatment. Despite the severe nature of the epilepsy, presence of concomitant psychiatric manifestations, and frequent need for poly-pharmacy associated with juvenile ceroid lipofuscinosis (JNCL, Batten disease) neither this disorder nor other subtypes of neuronal ceroid lipofuscinosis have previously been identified as risk factors for VHA/VHE. The aim of the present publication is to describe four cases with VHE in a well-defined Danish population of JNCL.

METHOD

An examination of medical records of all 35 patients with JNCL in Denmark was conducted and revealed fourteen patients treated with VPA.

RESULTS

Four patients treated with VPA developed VHE. All patients were prescribed VPA in standard dosages, had normal plasma concentrations of VPA and received antiepileptic drug (AED) polytherapy. Symptoms occurred shortly after commencement or increase in dose of VPA, and were quickly reversible upon discontinuation of VPA. Carnitine supplement was administrated in two patients, which resulted in resolution of symptoms and normalized ammonium levels.

CONCLUSION

Patients with JNCL are in great risk of developing VHA and VHE due to a high rate of polytherapy. Furthermore, studies have shown that carnitine level can be depressed in JNCL, which may increase the risk of VHA and VHE. We recommend that increased attention should be given to these patients.

Unusual cause of hyperammonemia in two cases with short-term and long-term valproate therapy successfully treated by single dose carglumic acid

Valproic acid (VPA) is an antiepileptic drug which is used in the treatment of various seizure disorders including tonic-clonic, myoclonic, absence, partial seizures and psychiatric disorders. VPA is usually well tolerated, but severe adverse effects may occur. Hyperammonaemic encephalopathy (HE) is a rare and potentially fatal complication of VPA treatment. The mechanism by which valproate induces hyperammonemia remains incompletely understood but is likely to relate to the urea cycle. Herein we present two cases with valproate-induced hyperammonemia at therapeutic valproate levels without signs of liver failure and were successfully treated by a single dose of carglumic acid.

Valproate (VPA)-associated hyperammonemic encephalopathy independent of elevated serum VPA levels: 21 cases in China from May 2000 to May 2012

Valproate (VPA) is a medication that is widely used in the treatment of neurological and psychiatric disorders, such as epilepsy and bipolar disorder. Valproate-induced hyperammonemic encephalopathy (VHE) is a rare central nervous system adverse effect of this medication that is characterized by impaired consciousness, which can range from drowsiness to coma; increased seizure frequency; acute cognitive symptoms; and gastrointestinal symptoms. In this manuscript, we report a single case and also review previous cases of VHE (n=20) in Chinese patients to identify risk factors for VHE. Increasing clinicians' awareness of VHE during concomitant VPA therapy is of utmost importance. Serum ammonia level is a useful and important diagnostic test. The discontinuation of VPA is currently the mainstay of treatment for VHE.

Valproic Acid and topiramate induced hyperammonemic encephalopathy in a patient with normal serum carnitine

A 17-year-old female developed hyperammonemic encephalopathy 2 weeks after valproic acid (VPA), 500 mg twice a day, was added to her regimen of topiramate (TPM), 200 mg twice a day. She presented to the emergency department (ED) with altered mental status, hypotension, bradycardia, and lethargy. Laboratory analysis showed mild non-anion gap hyperchloremic acidosis, serum VPA concentration of 86 mg/L, and urine drug screen result that was positive for marijuana. She was admitted to the pediatric intensive care unit for persistent symptoms, prolonged QTc, and medical history. Blood ammonia concentrations were obtained because of her persistent altered mental status, initially 94 μmol/L and a peak of 252 μmol/L. A serum carnitine profile was obtained at the time of hyperammonemia and was found to be normal (results were available postdischarge). VPA and TPM were discontinued on day 1 and day 2, respectively, as the patient's blood ammonia concentration remained elevated. On day 3, her mental status had returned to baseline, and blood ammonia concentrations trended downward; by day 4 her blood ammonia concentration was 23 μmol/L. VPA has been associated with numerous side effects including hyperammonemia and encephalopathy. Recently, drug interactions with TPM and VPA have been reported; however, serum carnitine concentrations have not been available. We discuss the possible mechanisms that VPA and TPM may affect serum ammonia and carnitine concentrations and the use of levocarnitine for patients or treating toxicity.

Adverse drug reactions induced by valproic acid

Valproic acid is a widely-used first-generation antiepileptic drug, prescribed predominantly in epilepsy and psychiatric disorders. VPA has good efficacy and pharmacoeconomic profiles, as well as a relatively favorable safety profile. However, adverse drug reactions have been reported in relation with valproic acid use, either as monotherapy or polytherapy with other antiepileptic drugs or antipsychotic drugs. This systematic review discusses valproic acid adverse drug reactions, in terms of hepatotoxicity, mitochondrial toxicity, hyperammonemic encephalopathy, hypersensitivity syndrome reactions, neurological toxicity, metabolic and endocrine adverse events, and teratogenicity.

Risk factors for hyperammonemia in pediatric patients with epilepsy

PURPOSE

To identify risk factors for hyperammonemia in pediatric patients with epilepsy.

METHODS

A total of 2,944 pediatric patients (ages 0-15 years) were classified into the following three groups: a group without drug treatment (n = 445, group I), a group receiving antiepileptic drugs other than valproic acid (VPA) (n = 673, group II), and a VPA-treated group (n = 1,826, group III). Hyperammonemia was defined as a plasma ammonia level exceeding 100 μg/dl with reference to the standard range and previous reports.

KEY FINDINGS

The mean ammonia level of groups I, II, and III was 36.0, 56.0, and 86.8 μg/dl, respectively, and the incidence of hyperammonemia was 1.6%, 7.7%, and 31.7%, respectively. In each group, the mean ammonia level of patients aged 3 years or younger was significantly higher than that of patients aged 4-15 years. In group II, concomitant use of topiramate and zonisamide were risk factors for hyperammonemia (adjusted odds ratio [OR] 3.9, 95% confidence interval [CI] 1.7-9.2, and OR 3.5, 95% CI 1.9-6.5, respectively). In group III, the ammonia level increased in a VPA dose-dependent manner. At a VPA dose of 30 mg/kg, there was 4.3-fold increase in the incidence of hyperammonemia. The other significant risk factors identified were female gender (OR 1.3, 95% CI 1.0-1.6), symptomatic generalized epilepsy (OR 1.4, 95% CI 1.1-1.8), and the concomitant use of phenytoin (OR 4.7, 95% CI 3.3-6.9), phenobarbital (OR 2.2. 95% CI 1.6-3.2), acetazolamide (OR 6.6, 95% CI 2.5-17.2), topiramate, or zonisamide.

SIGNIFICANCE

A young age and concomitant use of carbonic anhydrase inhibitors are associated with an increased risk of hyperammonemia regardless of whether the patient is taking VPA. In patients receiving VPA, concomitant use of phenytoin and/or phenobarbital enhances the risk of hyperammonemia. An increase in ammonia can be caused by multiple factors. Our results may help clinicians to avoid problems of hyperammonemia.

Hyperammonemia in children: on the crossroad of different disorders

BACKGROUND

Symptoms of hyperammonemia occur in patients irrespective of the kind of metabolic diseases. Age, metabolic and nutritional status, and decompensation factors such as infections influence clinical manifestations. Prolonged, untreated hyperammonemia leads to brain injury and intellectual disability. Treatment is directed at lowering plasma ammonia. Brain ammonium concentrations are 1.5 to 3.0 times higher than that in blood.

REVIEW SUMMARY

The authors discuss the pathophysiology of the symptoms and consequences of hyperammonemia in children, focusing on the metabolic disorders leading to an increased level of ammonia.

CONCLUSIONS

Ammonia toxicity has been investigated for a long time. According to the main hypotheses, the neurological alterations are connected to alterations in glutamatergic neurotransmission.

Topiramate increases the risk of valproic acid-induced encephalopathy

Metabolic encephalopathy is a rare but serious complication of valproic acid (VPA) therapy that usually presents with impaired consciousness or increased seizure frequency. Although it has been suggested that topiramate (TPM) increases the risk of VPA-induced encephalopathy, the additional risk in patients receiving TPM therapy has not been evaluated. We reviewed all adult patients who took VPA between January 2005 and February 2009 at the Seoul National University Hospital and identified patients with VPA-induced encephalopathy based on clinical and electroencephalography (EEG) data. Information on sex, age, serum ammonia level, serum VPA level, liver function test, and EEG was collected from patient registry and medical data. We enrolled 8,372 patients who received VPA therapy and 1,236 patients who received VPA/TPM combination therapy. We identified 11 patients with VPA-induced encephalopathy (0.13%), 7 of whom received a combination therapy of VPA and TPM. The odds ratio of VPA-induced encephalopathy with TPM over that without TPM was 10.16. There were no significant differences in sex distribution, number of antiepileptic agents, ammonia level, VPA serum level, underlying diseases, dosage of VPA, duration of VPA treatment, treatment of encephalopathy, and outcomes between the two groups. Our study showed that the prevalence of VPA-induced encephalopathy is approximately 0.1% among patients treated with VPA and that the risk of this condition, although still low, can increase by approximately 10 times in the presence of TPM therapy. Based on these results, we suggest that TPM should be carefully used in patients receiving VPA treatment.

Valproate-induced hyperammonemic encephalopathy: an update on risk factors, clinical correlates and management

INTRODUCTION

Valproate (VPA)-induced hyperammonemic encephalopathy (VHE) is a serious drug-related adverse effect characterized by lethargy, vomiting, cognitive slowing, focal neurological deficits and decreased levels of consciousness ranging from drowsiness to coma.

METHODS

We present a case series (n=5) and also review previous cases of VHE (n=30) in psychiatric patients to provide an update on risk factors, clinical correlates and management of VHE.

RESULTS

To our knowledge, there are 30 (16 female, 14 male) previously reported VHE cases in psychiatric patients. Risk factors for VHE include VPA-drug interactions, mental retardation, carnitine deficiency and presence of urea cycle disorders. Length of VPA treatment, VPA dosage, serum VPA levels and serum ammonia levels do not appear to correlate with onset or severity of VHE.VPA discontinuation is the primary treatment of VHE, although, l-carnitine, lactulose and neomycin have been used adjunctively in some patients.

CONCLUSION

Clinicians should consider VHE in patients taking VPA who present with lethargy, gastrointestinal symptoms, confusion and decreased levels of drowsiness. VPA discontinuation is currently the mainstay of treatment for VHE, although more research is warranted to delineate the underlying risk factors for VHE and consolidate treatment modalities for this potentially life-threatening drug adverse effect.

Risk factors for hyperammonemia associated with valproic acid therapy in adult epilepsy patients

Hyperammonemia is one of the side effects of treatment with valproic acid (VPA), but the risk factors and mechanisms involved remain obscure. This study analyzed the risk factors for hyperammonemia associated with VPA therapy in adult epilepsy patients. A retrospective analysis of 2724 Japanese patients (1217 males and 1507 females aged from 16 to 76years) treated with VPA between January 2006 and December 2010 were analyzed. The ammonia level increased markedly in a VPA dose-dependent manner, and was significantly elevated in patients who also used hepatic enzyme inducers such as phenytoin (PHT), phenobarbital (PB), carbamazepine (CBZ), and combinations of these drugs. When a blood ammonia level exceeding 200μg/dl was defined as hyperammonemia, the risk factors for hyperammonemia according to multiple regression analysis were a VPA dose >20mg/kg/day (odds ratio (OR): 4.1; 95% confidence interval (CI): 1.6-10.8) and concomitant use of PHT (OR: 11.0; 95% CI: 3.1-38.7), concomitant PB (OR: 4.3; 95% CI: 1.0-17.9), concomitant CBZ (OR: 2.8; 95% CI: 0.6-11.9), and concomitant topiramate (OR: 2.8; 95% CI: 1.2-6.5). Regimens containing multiple inducers were associated with an increased risk of hyperammonemia. Identification of risk factors for hyperammonemia associated with VPA therapy can help to minimize side effects during its clinical use.

Hyperammonemia in review: pathophysiology, diagnosis, and treatment

Ammonia is an important source of nitrogen and is required for amino acid synthesis. It is also necessary for normal acid-base balance. When present in high concentrations, ammonia is toxic. Endogenous ammonia intoxication can occur when there is impaired capacity of the body to excrete nitrogenous waste, as seen with congenital enzymatic deficiencies. A variety of environmental causes and medications may also lead to ammonia toxicity. Hyperammonemia refers to a clinical condition associated with elevated ammonia levels manifested by a variety of symptoms and signs, including significant central nervous system (CNS) abnormalities. Appropriate and timely management requires a solid understanding of the fundamental pathophysiology, differential diagnosis, and treatment approaches available. The following review discusses the etiology, pathogenesis, differential diagnosis, and treatment of hyperammonemia.

Hyperammonemic encephalopathy related to valproate, phenobarbital, and topiramate synergism

We present a woman with epilepsy secondary to a lesion in the left frontal lobe. She developed episodes of disorientation and behavioral changes. She was taking valproic acid (1500 mg/day), topiramate (200 mg/day), and phenobarbital (100 mg/day). During an episode, the EEG revealed moderate encephalopathy and ammonia levels were increased (195 μg/dL, reference range: 11-60 μg/dL). Episodes ceased after withdrawal of valproic acid.