Science review: carnitine in the treatment of valproic acid-induced toxicity - what is the evidence?

L-carnitine for valproic acid-induced toxicity

AIMS

Review the effectiveness and dosing of L-carnitine for valproic-acid induced toxicity.

METHODS

A literature review of the pharmacokinetics and clinical use of L-carnitine was performed.

RESULTS

Valproic acid is a fatty acid used for numerous therapeutic indications ranging from epilepsy to bipolar disorder. The metabolism of valproic acid produces both therapeutic and toxic metabolites. Whilst it has a good safety profile, adverse effects of valproic acid in chronic use include hepatotoxicity ranging from transient elevation of liver enzymes to fulminant liver failure and hyperammonaemia with resultant encephalopathy. L-carnitine is an essential cofactor for mitochondrial fatty acid metabolism, which is an important source of energy in cardiac and skeletal muscle. Physiological concentrations of L-carnitine are maintained in man by exogenous dietary intake and endogenous synthesis. Following exogenous oral administration of L-carnitine, the bioavailability ranges from 14% to 18%. After bolus intravenous administration of L-carnitine in doses ranging from 20 to 100 mg/kg, the volume of distribution is 0.2-0.3 L/kg, and the fraction excreted unchanged in urine is 0.73-0.95, suggesting that renal clearance of L-carnitine is dose dependent due to saturable renal reabsorption at supraphysiological concentrations.

CONCLUSIONS

There is evidence supporting the use of L-carnitine in treating hyperammonaemia and hepatotoxicity following chronic therapeutic use and after acute overdose of valproic acid, but the optimal dose and route of administration is unknown. Based on the pharmacokinetics of L-carnitine, we advocate the administration of L-carnitine for valproic-acid induced hyperammonaemia or hepatotoxicity as an intravenous loading dose of 5 mg/kg followed by a continuous intravenous infusion instead of the oral or intravenous boluses that are currently advocated.

A strategy to detect metabolic changes induced by exposure to chemicals from large sets of condition-specific metabolic models computed with enumeration techniques

BACKGROUND

The growing abundance of in vitro omics data, coupled with the necessity to reduce animal testing in the safety assessment of chemical compounds and even eliminate it in the evaluation of cosmetics, highlights the need for adequate computational methodologies. Data from omics technologies allow the exploration of a wide range of biological processes, therefore providing a better understanding of mechanisms of action (MoA) related to chemical exposure in biological systems. However, the analysis of these large datasets remains difficult due to the complexity of modulations spanning multiple biological processes.

RESULTS

To address this, we propose a strategy to reduce information overload by computing, based on transcriptomics data, a comprehensive metabolic sub-network reflecting the metabolic impact of a chemical. The proposed strategy integrates transcriptomic data to a genome scale metabolic network through enumeration of condition-specific metabolic models hence translating transcriptomics data into reaction activity probabilities. Based on these results, a graph algorithm is applied to retrieve user readable sub-networks reflecting the possible metabolic MoA (mMoA) of chemicals. This strategy has been implemented as a three-step workflow. The first step consists in building cell condition-specific models reflecting the metabolic impact of each exposure condition while taking into account the diversity of possible optimal solutions with a partial enumeration algorithm. In a second step, we address the challenge of analyzing thousands of enumerated condition-specific networks by computing differentially activated reactions (DARs) between the two sets of enumerated possible condition-specific models. Finally, in the third step, DARs are grouped into clusters of functionally interconnected metabolic reactions, representing possible mMoA, using the distance-based clustering and subnetwork extraction method. The first part of the workflow was exemplified on eight molecules selected for their known human hepatotoxic outcomes associated with specific MoAs well described in the literature and for which we retrieved primary human hepatocytes transcriptomic data in Open TG-GATEs. Then, we further applied this strategy to more precisely model and visualize associated mMoA for two of these eight molecules (amiodarone and valproic acid). The approach proved to go beyond gene-based analysis by identifying mMoA when few genes are significantly differentially expressed (2 differentially expressed genes (DEGs) for amiodarone), bringing additional information from the network topology, or when very large number of genes were differentially expressed (5709 DEGs for valproic acid). In both cases, the results of our strategy well fitted evidence from the literature regarding known MoA. Beyond these confirmations, the workflow highlighted potential other unexplored mMoA.

CONCLUSION

The proposed strategy allows toxicology experts to decipher which part of cellular metabolism is expected to be affected by the exposition to a given chemical. The approach originality resides in the combination of different metabolic modelling approaches (constraint based and graph modelling). The application to two model molecules shows the strong potential of the approach for interpretation and visual mining of complex omics in vitro data. The presented strategy is freely available as a python module ( https://pypi.org/project/manamodeller/ ) and jupyter notebooks ( https://github.com/LouisonF/MANA ).

A Rare Case Report of Hypoketotic Hypoglycemia Induced Seizures Due to Secondary Carnitine Deficiency in a 44-year-old Female

Carnitine deficiency is a rare metabolic condition that can result in fasting hypoglycemia. Carnitine deficiency could be primary or secondary to other conditions. Among secondary causes, antiepileptics such as valproic acid have been incriminated. Valproic acid is known to deplete carnitine stores and inhibit the process of β-oxidation. Herein we report the case of a 44-year-old female with epilepsy that presented with breakthrough seizures associated with hypoglycemia despite being on appropriate antiepileptic therapy. The patient was later found to have carnitine deficiency. Discontinuation of valproic acid and supplementation with l-carnitine resolved the patient's hypoglycemia and breakthrough seizures. With this case report, we hope to encourage clinicians to include carnitine deficiency in the differential diagnosis of unexplained hypoglycemia.

Gas-Phase Ion/Ion Reactions to Enable Radical-Directed Dissociation of Fatty Acid Ions: Application to Localization of Methyl Branching

Methyl branching on the carbon chains of fatty acids and fatty esters is among the structural variations encountered with fatty acids and fatty esters. Branching in fatty acid/ester chains is particularly prominent in bacterial species and, for example, in vernix caseosa and sebum. The distinction of branched chains from isomeric straight-chain species and the localization of branching can be challenging to determine by mass spectrometry (MS). Condensed-phase derivatization strategies, often used in conjunction with separations, are most commonly used to address the identification and characterization of branched fatty acids. In this work, a gas-phase ion/ion strategy is presented that obviates condensed-phase derivatization and introduces a radical site into fatty acid ions to facilitate radical-directed dissociation (RDD). The gas-phase approach is also directly amenable to fatty acid anions generated via collision-induced dissociation from lipid classes that contain fatty esters. Specifically, divalent magnesium complexes bound to two terpyridine ligands that each incorporate a ((2,2,6,6-tetramethyl-1-piperidine-1-yl)oxy) (TEMPO) moiety are used to charge-invert fatty acid anions. Following the facile loss of one of the ligands and the TEMPO group of the remaining ligand, a radical site is introduced into the complex. Subsequent collision-induced dissociation (CID) of the complex exhibits preferred cleavages that localize the site(s) of branching. The approach is illustrated with iso-, anteiso-, and isoprenoid branched-chain fatty acids and an intact glycerophospholipid and is applied to a mixture of branched- and straight-chain fatty acids derived from Bacillus subtilis.

Carbapenems as Antidotes for the Management of Acute Valproic Acid Poisoning

INTRODUCTION

Valproic acid (VPA) is a broad-spectrum drug primarily used in the treatment of epilepsy and bipolar disorder. It is not an uncommon occurrence for VPA to cause intoxication. The established treatment of VPA poisoning includes supportive care, multiple doses of activated charcoal, levocarnitine and hemodialysis/hemoperfusion. There is a clinically significant interaction between carbapenem antibiotics and VPA. By affecting enterohepatic recirculation, carbapenems can increase the overall VPA clearance from the blood of intoxicated patients. It is suggested that carbapenems could successfully be used as antidotes in the treatment of acute VPA poisonings.

THE AIM

To evaluate the effectiveness of carbapenems in the treatment of patients acutely poisoned by VPA.

PATIENTS AND METHODS

This retrospective study included patients acutely poisoned by VPA and treated with carbapenems at the Department of Clinical Toxicology at the Military Medicinal Academy in Serbia for a two-year period.

RESULTS

After the admission, blood concentrations of VPA kept increasing, reaching their peak at 114-724 mg/L, while the mental state of the patients continued to decline, prompting a decision to introduce carbapenems. After the introduction of carbapenems, the concentrations of the drug dropped by 46-93.59% (average 72%) followed by rapid recovery of consciousness. Ten out of eleven patients had positive outcomes, while one patient died. The most commonly observed complication in our group of patients was bronchopneumonia.

CONCLUSIONS

The application of carbapenems for the management of acute VPA poisoning might be a useful and effective treatment option.

The implication of LPS/TLR4 and FXR receptors in hepatoprotective efficacy of indole-3-acetic acid and chenodeoxycholic acid

AIM

Valproic acid (VPA) belongs to the first-generation antiepileptic drugs, yet its prolonged use can cause life-threatening liver damage. The importance of our study is to investigate the protective effect of indole-3-acetic acid (IAA), chenodeoxycholic acid (CDCA) and their combination on VPA-induced liver injury focusing on lipopolysaccharides (LPS)/toll-like receptor 4 (TLR4) pathway and farnesoid X receptor (FXR).

METHODS

Thirty rats were randomly assigned into five groups, normal control group, VPA group received 500 mg/kg of VPA intraperitoneally. The remaining groups were orally treated with either 40 mg/kg of IAA, 90 mg/kg of CDCA, or a combination of both, along with VPA. All treatments were administered one hour after the administration of VPA for three weeks.

KEY FINDINGS

VPA group showed significant elevations in the liver weight/body weight ratio, serum aminotransferases, triglyceride, and total cholesterol levels. Hepatic glutathione (GSH) level and superoxide dismutase (SOD) activity were significantly decreased, while malondialdehyde (MDA) level, tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), lipopolysaccharide (LPS) and caspase 3 were significantly increased. Likewise, immunohistochemical analysis revealed that TLR4 expression was elevated, whereas FXR expression was downregulated in hepatocytes. IAA substantially ameliorated all previously altered parameters, whereas CDCA treatment showed a partial improvement compared to IAA. Surprisingly, combination therapy of IAA with CDCA showed an additive effect only in the hepatic expression of TLR4 and FXR proteins.

SIGNIFICANCE

IAA could be a promising protective agent against VPA-induced liver injury.

Metabolomic Analysis of Pediatric Patients with Idiosyncratic Drug-Induced Liver Injury According to the Updated RUCAM

Hepatotoxicity, a common adverse drug effect, has been extensively studied in adult patients. However, it is equally important to investigate this condition in pediatric patients to develop personalized treatment strategies for children. This study aimed to identify plasma biomarkers that characterize hepatotoxicity in pediatric patients through an observational case-control study. Metabolomic analysis was conducted on 55 pediatric patients with xenobiotic liver toxicity and 88 healthy controls. The results revealed clear differences between the two groups. Several metabolites, including hydroxydecanoylcarnitine, octanoylcarnitine, lysophosphatidylcholine, glycocholic acid, and taurocholic acid, were identified as potential biomarkers (area under the curve: 0.817; 95% confidence interval: 0.696-0.913). Pathway analysis indicated involvement of primary bile acid biosynthesis and the metabolism of taurine and hypotaurine (p < 0.05). The findings from untargeted metabolomic analysis demonstrated an increase in bile acids in children with hepatotoxicity. The accumulation of cytotoxic bile acids should be further investigated to elucidate the role of these metabolites in drug-induced liver injury.

Antidotes in Clinical Toxicology-Critical Review

Poisoning and overdose are very important aspects in medicine and toxicology. Chemical weapons pose a threat to civilians, and emergency medicine principles must be followed when dealing with patients who have been poisoned or overdosed. Antidotes have been used for centuries and modern research has led to the development of new antidotes that can accelerate the elimination of toxins from the body. Although some antidotes have become less relevant due to modern intensive care techniques, they can still save lives or reduce the severity of toxicity. The availability of antidotes is crucial, especially in developing countries where intensive care facilities may be limited. This article aims to provide information on specific antidotes, their recommended uses, and potential risks and new uses. In the case of poisoning, supportive therapies are most often used; however, in many cases, the administration of an appropriate antidote saves the patient's life. In this review, we reviewed the literature on selected antidotes used in the treatment of poisonings. We also characterised the antidotes (bio)chemically. We described the cases in which they are used together with the dosage recommendations. We also analysed the mechanisms of action. In addition, we described alternative methods of using a given substance as a drug, an example of which is N-acetylcysteine, which can be used in the treatment of COVID-19. This article was written as part of the implementation of the project of the Polish Ministry of Education and Science, "Toxicovigilance, poisoning prevention, and first aid in poisoning with xenobiotics of current clinical importance in Poland", grant number SKN/SP/570184/2023.

Drug-Induced Acute-on-Chronic Liver Failure: Challenges and Future Directions

Drug-induced liver injury (DILI) is a global problem related to prescription and over-the-counter medications as well as herbal and dietary supplements. It can lead to liver failure with the risk of death and need for liver transplantation. Acute-on-chronic liver failure (ACLF) may be precipitated by DILI and is associated with a high risk of mortality. This review addresses the challenges in defining the diagnostic criteria of drug-induced ACLF (DI-ACLF). The studies characterizing DI-ACLF and its outcomes are summarized, highlighting geographic differences in underlying liver disease and implicated agents, as are future directions in the field.

Predicting Valproate-Induced Liver Injury Using Metabolomic Analysis of Ex Ovo Chick Embryo Allantoic Fluid

The use of sensitive animals in toxicological studies tends to be limited. Even though cell culture is an attractive alternative, it has some limitations. Therefore, we investigated the potential of the metabolomic profiling of the allantoic fluid (AF) from ex ovo chick embryos to predict the hepatotoxicity of valproate (VPA). To this end, the metabolic changes occurring during embryo development and following exposure to VPA were assessed using ¹H-NMR spectroscopy. During embryonic development, our findings indicated a metabolism progressively moving from anaerobic to aerobic, mainly based on lipids as the energy source. Next, liver histopathology of VPA-exposed embryos revealed abundant microvesicles indicative of steatosis and was metabolically confirmed via the determination of lipid accumulation in AF. VPA-induced hepatotoxicity was further demonstrated by (i) lower glutamine levels, precursors of glutathione, and decreased β-hydroxybutyrate, an endogenous antioxidant; (ii) changes in lysine levels, a precursor of carnitine, which is essential in the transport of fatty acids to the mitochondria and whose synthesis is known to be reduced by VPA; and (iii) choline accumulation that promotes the export of hepatic triglycerides. In conclusion, our results support the use of the ex ovo chick embryo model combined with the metabolomic assessment of AF to rapidly predict drug-induced hepatotoxicity.

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.

Valproate-induced hyperammonemic encephalopathy treated by L-ornithine-L-aspartate: a case report

A 63-year-old man developed reduced consciousness and dysphagia progressively. Examination and parameters were normal, except for a Glasgow Coma Scale score of seven, and his grading on the swallow water test increased from grade 1 to grade 5. Brain imaging and blood tests were unexplainable except by high plasma ammonia. His past medical history included cerebral infarction, hypertension and epilepsy induced by cerebral hyperperfusion syndrome. He was rceiving antiepileptic treatment of continuously intravenously pumped sodium valproate of 64 mg/h for 4 days, which overlapped for 12 hours with taking 500 mg sustained release tablets. Sodium valproate was stopped; testing demonstrated normal plasma concentrations of sodium valproate and elevated concentrations of ammonia. Ornithine aspartate was administrated. The patient's level of responsiveness and ammonia levels gradually improved. The patient was also being treated with ceftriaxone sodium for a hypostatic pneumonia and with desmopressin for diabetes insipidus. There is an association between sodium valproate and hyperammonaemia and encephalopathy. Immediate recognition of the serious but uncommon adverse effects is essential. To our knowledge this is the first report of ornithine aspartate being used in this disorder.

Valproate-Associated Transaminitis and Rhabdomyolysis

Valproic acid (VPA), a common anti-epileptic with prevalent use, has many side effects such as alopecia, abdominal discomfort, thrombocytopenia, etc. Other than those documented, publications cite the drug's rare side effects, such as hepatotoxicity, coagulation disorders, hyperammonemic encephalopathy, rhabdomyolysis, etc. We present the case of a 24-year-old man who was started on valproic acid after a seizure episode and developed mild transaminitis and rhabdomyolysis within 24 hours of drug initiation. Cessation of the drug led to the resolution of raised creatinine kinase and transaminase levels.

Embryonic exposure to acetyl-L-carnitine protects against valproic acid-induced cardiac malformation in zebrafish model

Worldwide, estimated counts of about 7.9 million children are born with serious birth defects. In addition to genetic factors, prenatal exposure to drugs and environmental toxicants represents a major contributing factor to congenital malformations. In earlier investigation, we explored cardiac malformation caused by valproic acid (VPA) during early developing stages of zebrafish. Since heart depends on mitochondrial fatty acid oxidative metabolism for energy demands in which carnitine shuttle has a major role, the present study aimed to investigate the effect of acetyl-L-carnitine (AC) against VPA-induced cardiac malformation in developing zebrafish. Initially, AC was subjected to toxicological evaluation, and two micromolar concentrations (25 µM and 50 µM) were selected for evaluation. A sub-lethal concentration of VPA (50 µM) was selected to induce cardiac malformation. The embryos were grouped and the drug exposures were made at 2.5 h post-fertilization (hpf). The cardiac development and functioning was monitored. A progressive decline in cardiac functioning was noted in group exposed to VPA 50 µM. At 96 hpf and 120 hpf, the morphology of heart was severely affected with the chambers which became elongated and string-like accompanied by histological changes. Acridine orange staining showed accumulation of apoptotic cells. Group exposed to VPA 50 µM with AC 50 µM showed a significant reduction in pericardial sac edema with morphological, functional and histological recovery in developing heart. Moreover, reduced number of apoptotic cells was noted. The improvement with AC might be due to restoration of carnitine homeostasis for cardiac energy metabolism in developing heart.

The effect of sodium benzoate, L-carnitine, and phenylacetate on valproate-induced hyperammonemia in Male Wistar rats

INTRODUCTION

L-carnitine (LC) is commonly used in the treatment of valproate-induced hyperammonemia (VIHA). LC prevents the production of ammonia with no significant effect on renal ammonia excretion. This study was conducted to evaluate the effect of sodium benzoate (SB) and phenyl acetate (PA) on reducing VIHA.

MATERIALS AND METHODS

Eight groups treated with Sodium Valproate (SV) at 300 mg/kg and 15 minutes later with normal saline, SB (144 mg/kg), PA (0.3 g/kg), LC (2.5 g/kg), SB (144 mg/kg) plus PA (0.3 g/kg), or SB (144 mg/kg) plus PA (0.3 g/kg) plus LC (2.5 g/kg), intraperitoneally. Other groups were exposed to normal saline, SB, LC or PA alone. Animal's motor function and serum ammonia, lactate, and sodium levels were assessed at 0.5, 1, and 1.5 hours after the SV injection.

RESULTS

The results showed that LC reduced SV-induced hyperammonemia just at one and half-hour after treatment (P<0.001). PA, alone or in combination with other antidotes, reduced serum ammonia at all evaluated times (P<0.001). LC improved the impaired motor function of animals only at 1.5 hours, while PA, alone or in combination decreased the motor function scores at different times. However, SB administration alone did not change SV-induced hyperammonemia or motor function impairment. There was no significant difference in the level of serum aminotransferases, blood urea nitrogen, and creatinine between groups.

CONCLUSION

These findings define that PA had a better therapeutic effect on valproate-induced hyperammonemia in comparison with SB. Co-administration of LC with PA ameliorated the elevated levels of ammonia and may relieve potential therapeutic application against acute SV intoxication.

Valproic Acid Overdose: Case Report and Literature Review

BACKGROUND

Valproic acid (VPA) is a common antiepileptic drug that is also used routinely for various psychiatric disorders. VPA toxicity typically manifests as central nervous system depression, while hyperammonemic encephalopathy and hepatotoxicity are potentially life-threatening complications.

CASE REPORT

We describe the case of a 56-year-old man who presented to the emergency department after an intentional VPA overdose, was found to have hyperammonemia, and was treated with L-carnitine exclusively. He was subsequently admitted to the hospital for monitoring and serial laboratory testing. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Although VPA toxicity has conventionally been managed by gastric decontamination, L-carnitine, and, in severe and refractory cases, extracorporeal removal, recent literature supports the use of carbapenem antibiotics, particularly meropenem. Thus, we report the details of current treatment modalities for VPA toxicity by reviewing current literature.

Valproic Acid Serum Concentration and Incidence of Toxicity in Pediatric Patients

In certain pediatric patients on valproic acid, therapeutic range (50-100 μg/mL) is maximized or exceeded to achieve better seizure control. This study compared incidence of common valproic acid adverse effects (thrombocytopenia, hepatotoxicity, and hyperammonemia) across maintenance concentration and age group. One hundred twenty-four children on maintenance valproic acid between January 2013 and January 2021 were eligible for inclusion. Fifty-six patients were maintained in concentration range 50 to 80 μg/mL, an additional 44 between 80 and 100 μg/mL and 24 between 100 and 120 μg/mL. Forty-one patients were prepubescent, 57 pubescent, and 26 postpubescent. There were no statistically significant differences observed in the primary endpoint of thrombocytopenia across serum concentration range (P = .093) or age group (P = .628). No significant differences in hepatic dysfunction (P = .099) or hyperammonemia (P = .548) were observed in serum concentration groups. Similarly, age group analysis observed no difference in hepatic dysfunction (P = .615) or hyperammonemia (P = .369). Serum valproic acid levels >100 μg/mL can be considered in select pediatric patients based on this study.

Carnitine and Depression

Depression has become one of the most common mental diseases in the world, but the understanding of its pathogenesis, diagnosis and treatments remains insufficient. Carnitine is a natural substance that exists in organisms, which can be synthesized in vivo or supplemented by intake. Relationships of carnitine with depression, bipolar disorder and other mental diseases have been reported in different studies. Several studies show that the level of acylcarnitines (ACs) changes significantly in patients with depression compared with healthy controls while the supplementation of acetyl-L-carnitine is beneficial to the treatment of depression. In this review, we aimed to clarify the effects of ACs in depressive patients and to explore whether ACs might be the biomarkers for the diagnosis of depression and provide new ideas to treat depression.

Pharmacotherapies for Drug-Induced Liver Injury: A Current Literature Review

Drug-induced liver injury (DILI) has become a serious public health problem. For the management of DILI, discontinuation of suspicious drug or medicine is the first step, but the treatments including drugs and supporting approaches are needed. Reference to clinical patterns and disease severity grades of DILI, the treatment drugs were considered to summarize into hepatoprotective drugs (N-acetylcysteine and Glutathione, Glycyrrhizin acid preparation, Polyene phosphatidylcholine, Bicyclol, Silymarin), anticholestatic drug (Ursodeoxycholic acid, S-adenosylmethionine, Cholestyramine), immunosuppressants (Glucocorticoids) and specific treatment agents (L-carnitine, Anticoagulants). The current article reviewed the accumulated literature with evidence-based medicine researches for DILI in clinical practice. Also the drawbacks of the clinical studies involved in the article, unmet needs and prospective development for DILI therapy were discussed.

Serum free carnitine levels in children with Kawasaki disease

BACKGROUND

Carnitine plays an essential role in the transfer of long-chain fatty acids to the mitochondria for β-oxidation. No study has characterized carnitine in children with Kawasaki disease (KD). The objective of this study was to elucidate the characteristics of serum free carnitine (FC) in hospitalized pediatric patients with KD.

METHODS

We retrospectively analyzed 45 patients with KD in whom serum FC levels were measured. We investigated the clinical and laboratory parameters before intravenous immunoglobulin was administered, including serum FC levels, according to the response to intravenous immunoglobulin (IVIG). We also analyzed the relationship among serum FC, laboratory data, and clinical variables.

RESULTS

IVIG was effective in 33 children (responders) and was ineffective in 12 children (non-responders). Serum FC levels were higher in non-responders than in responders: 35.3 μmol/L (range, 26.8-118.4 μmol/L) vs 31.4 μmol/L (range, 20.9-81.2 μmol/L), P <0.05. FC levels before IVIG in 80% of responders were below the normal range. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin, and FC were higher in non-responders than in responders. FC levels were correlated with AST (R² = 0.364, P = 0.0015) and ALT (R² = 0.423, P < 0.001) levels.

CONCLUSIONS

Free carnitine levels were elevated in some patients with KD, especially in those who were refractory to IVIG. Additionally, FC levels in children with KD correlated with ASL and ALT levels.

The role of efflux transporters and metabolizing enzymes in brain and peripheral organs to explain drug-resistant epilepsy

Drug‐resistant epilepsy has been explained by different mechanisms. The most accepted one involves overexpression of multidrug transporters proteins at the blood brain barrier and brain metabolizing enzymes. This hypothesis is one of the main pharmacokinetic reasons that lead to the lack of response of some antiseizure drug substrates of these transporters and enzymes due to their limited entrance into the brain and limited stay at the sites of actions. Although uncontrolled seizures can be the cause of the overexpression, some antiseizure medications themselves can cause such overexpression leading to treatment failure and thus refractoriness. However, it has to be taken into account that the inductive effect of some drugs such as carbamazepine or phenytoin not only impacts on the brain but also on the rest of the body with different intensity, influencing the amount of drug available for the central nervous system. Such induction is not only local drug concentration but also time dependent. In the case of valproic acid, the deficient disposition of ammonia due to a malfunction of the urea cycle, which would have its origin in an intrinsic deficiency of L‐carnitine levels in the patient or by its depletion caused by the action of this antiseizure drug, could lead to drug‐resistant epilepsy. Many efforts have been made to change this situation. In order to name some, the administration of once‐daily dosing of phenytoin or the coadministration of carnitine with valproic acid would be preferable to avoid iatrogenic refractoriness. Another could be the use of an adjuvant drug that down‐regulates the expression of transporters. In this case, the use of cannabidiol with antiseizure properties itself and able to diminish the overexpression of these transporters in the brain could be a novel therapy in order to allow penetration of other antiseizure medications into the brain.

Non-hyperammonaemia valproate-induced encephalopathy: A case report

WHAT IS KNOWN AND OBJECTIVE

Valproate sodium is an effective antiepileptic drug (AED). Serious adverse effects of valproate sodium are uncommon. This case report illustrates the existence of non-hyperammonaemia valproate-induced encephalopathy.

CASE DESCRIPTION

A 47-year-old woman with epilepsy who developed valproate-induced encephalopathy without hyperammonaemia after valproate sodium treatment, and the symptoms completely subsided after withdrawal of valproate sodium.

WHAT IS NEW AND CONCLUSION

Early diagnosis and identification of the mechanisms of non-hyperammonaemia valproate-induced encephalopathy are important. Immediate discontinuation of valproate sodium results in rapid resolution of symptoms in these patients.

Personalised therapeutic management of epileptic patients guided by pathway-driven breath metabolomics

BACKGROUND

Therapeutic management of epilepsy remains a challenge, since optimal systemic antiseizure medication (ASM) concentrations do not always correlate with improved clinical outcome and minimal side effects. We tested the feasibility of noninvasive real-time breath metabolomics as an extension of traditional therapeutic drug monitoring for patient stratification by simultaneously monitoring drug-related and drug-modulated metabolites.

METHODS

This proof-of-principle observational study involved 93 breath measurements of 54 paediatric patients monitored over a period of 2.5 years, along with an adult's cohort of 37 patients measured in two different hospitals. Exhaled breath metabolome of epileptic patients was measured in real time using secondary electrospray ionisation-high-resolution mass spectrometry (SESI-HRMS).

RESULTS

We show that systemic ASM concentrations could be predicted by the breath test. Total and free valproic acid (VPA, an ASM) is predicted with concordance correlation coefficient (CCC) of 0.63 and 0.66, respectively. We also find (i) high between- and within-subject heterogeneity in VPA metabolism; (ii) several amino acid metabolic pathways are significantly enriched (p < 0.01) in patients suffering from side effects; (iii) tyrosine metabolism is significantly enriched (p < 0.001), with downregulated pathway compounds in non-responders.

CONCLUSIONS

These results show that real-time breath analysis of epileptic patients provides reliable estimations of systemic drug concentrations along with risk estimates for drug response and side effects.

Practical considerations of dietary therapies for epilepsy in adults

Despite the increasing number of anti-seizure medications becoming available, the proportion of patients with drug-resistant epilepsy remains unchanged. Dietary therapy for epilepsy is well-established practice in paediatric care, but relatively underutilised in adults. Recently, international recommendations have been published to guide the treatment of adults receiving dietary therapy for epilepsy.

This review focuses on the specific aspects of care unique to the management of adults receiving dietary therapy for epilepsy, including patient selection, diet composition, initiation, monitoring and cessation of dietary treatment. We emphasise the need for a multidisciplinary team approach with appropriately trained neurologists and dietitians to provide holistic care while the patients are receiving dietary therapy. Future research should focus on the optimal diet composition and meeting the psychosocial needs of adults with epilepsy to maximise efficacy and adherence to dietary treatment.

Valproic acid-induced encephalopathy: A review of clinical features, risk factors, diagnosis, and treatment

Valproic acid (VPA), or sodium valproate, is a commonly used medication for seizure disorders, migraines, and mental illness. Although VPA is relatively safe, it still has several adverse effects; among these, VPA-induced encephalopathy is the most serious. Valproic acid-induced encephalopathy mainly manifests as acute or subacute encephalopathy and has been associated with hyperammonemia, L-carnitine deficiency, and urea cycle enzyme dysfunction. Delayed identification of VPA-induced encephalopathy could be potentially fatal. Here, we perform an extensive review of relevant literature pertaining to VPA-induced encephalopathy, including its epidemiology, clinical features, possible pathophysiology, risk factors, diagnosis, and treatment.

Valproate-Induced Hyperammonemic Encephalopathy Following Accidental Ingestion in a Toddler

Clinical manifestations of valproic acid (VPA) toxicity can range from just mild confusion and drowsiness to serious encephalopathy, leading to depressed sensorium and even coma and death. The exact cause(s) of how VPA influences the integrity of brain function remains unknown. Nevertheless, several mechanisms have been postulated including a surge in the blood ammonia concentration. Valproic acid-induced hyperammonemic encephalopathy is a rare yet serious sequalae and that can lead to grave outcomes. We report a case of hyperammonemic encephalopathy with preserved liver function following a moderate VPA intoxication in a toddler, who was successfully managed conservatively. Additionally, we briefly discuss mechanistic basis of VPA toxicity and highlight some of the available potential therapies.

The Effect of acetyl-L-carnitine, Alpha-lipoic Acid, and Coenzyme Q10 Combination in Preventing Anti-tuberculosis Drug-induced Hepatotoxicity: A Randomized, Double-blind, Placebo-controlled Clinical Trial

Drug-induced liver injury (DILI) is one of the most serious adverse effects of anti-tuberculosis (TB) drugs. A suggested mechanism of this adverse effect is mitochondrial dysfunction (MDF). The purpose of this study was an evaluation of the possible preventive effects of the combination of acetyl-L-carnitine (ALCAR), alpha-lipoic acid (ALA), and coenzyme Q10 (CoQ10), as mitochondrial nutrients (MNs), against anti-TB DILI. In this clinical trial, patients who met the inclusion criteria were randomly assigned to either experimental (n = 44) or placebo (n = 43) groups. The experimental group received capsules containing CoQ10 (200 mg) + ALA (250 mg) + ALCAR (250 mg) orally twice daily for two weeks, and the placebo group received oral placebo capsules with the same interval and duration. The mean serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total bilirubin (TBil) at the end of the first and second weeks as well as the incidence of DILI during the intervention were recorded and compared between the two groups. At the end of the study, the mean serum levels of AST and ALT in the experimental group were significantly lower than the placebo group (36.27 ± 36.43 vs. 86.02 ± 97.23 and 28.41 ± 27.41 vs. 78.80 ± 118.28, respectively, P = 0.003 for both). Also, the incidence of anti-TB DILI was significantly lower in the experimental group than the placebo group (6.8% vs. 25.6%, P = 0.017). In conclusion, using the combination of ALCAR, ALA, and CoQ10 may provide an effective strategy in preventing anti-TB DILI.

An Examination of Serum Acylcarnitine and Amino Acid Profiles at Different Time Point of Ketogenic Diet Therapy and Their Association of Ketogenic Diet Effectiveness

Background: This study aimed to identify metabolic parameters at different time points of ketogenic diet therapy (KDT) and investigate their association with response to KDT in pediatric drug-resistant epilepsy (DRE). Methods: Prospectively, twenty-nine patients (0.67~20 years old) with DRE received classic ketogenic diet with non-fasting, gradual KD initiation protocol (GRAD-KD) for 1 year were enrolled. A total of 22 patients remaining in study received blood examinations at baseline, 3rd, 6th, 9th, and 12th months of KDT. β-hydroxybutyrate, free carnitine, acylcarnitines, and amino acids were compared between responders (seizure reduction rate ≥ 50%) and non-responders (seizure reduction rate < 50%) to identify the effectiveness of KDT. Results: The 12-month retention rate was 76%. The responders after 12 months of KDT were 59% (13/22). The free carnitine level decreased significantly at 9th months (p < 0.001) but increased toward baseline without symptoms. Propionyl carnitine (C3), Isovaleryl carnitine (C5), 3-Hydroxyisovalerylcarnitine (C5:OH) and methylmalonyl carnitine (C4-DC) decreased but 3-hydroxybutyrylcarnitine (C4:OH) increased significantly at 12th months of KDT. The glycine level was persistently higher than baseline after KDT. KDT responders had lower baseline C3 and long-chain acylcarnitines, C14 and C18, as well as lower C5, C18, and leucine/isoleucine. Conclusions: KDT should be avoided in patients with non-ketotic hyperglycemia. Routine carnitine supplementation is not recommended because hypocarnitinemia was transient and asymptomatic during KDT. Better mitochondrial βoxidation function associates with greater KDT response.

Principles of Pharmacotherapy of Seizures and Status Epilepticus

Status epilepticus is a neurological emergency with an outcome that is highly associated with the initial pharmacotherapy management that must be administered in a timely fashion. Beyond first-line therapy of status epilepticus, treatment is not guided by robust evidence. Optimal pharmacotherapy selection for individual patients is essential in the management of seizures and status epilepticus with careful evaluation of pharmacokinetic and pharmacodynamic factors. With the addition of newer antiseizure agents to the market, understanding their role in the management of status epilepticus is critical. Etiology-guided therapy should be considered in certain patients with drug-induced seizures, alcohol withdrawal, or autoimmune encephalitis. Some patient populations warrant special consideration, such as pediatric, pregnant, elderly, and the critically ill. Seizure prophylaxis is indicated in select patients with acute neurological injury and should be limited to the acute postinjury period.

Severe Pancytopenia Induced by Valproic Acid

Valproic acid is commonly used to treat pediatric epilepsy. This drug is usually well-tolerated; its side effects are typically mild, with hepatotoxicity being the most widely recognized one. Bone marrow suppression is a rarely seen complication in patients with valproic acid levels more than 125 mcg/mL. Reported cases indicate an increased incidence of hematologic toxicity; however, evidence for management is limited. We report a case of bone marrow suppression induced by a high dose of valproic acid in a 10-year-old male.

Drug induced liver injury: an update

Drug induced liver injury (DILI) is a relatively rare hepatic condition in response to the use of medications, illegal drugs, herbal products or dietary supplements. It occurs in susceptible individuals through a combination of genetic and environmental risk factors believed to modify drug metabolism and/or excretion leading to a cascade of cellular events, including oxidative stress formation, apoptosis/necrosis, haptenization, immune response activation and a failure to adapt. The resultant liver damage can present with an array of phenotypes, which mimic almost every other liver disorder, and varies in severity from asymptomatic elevation of liver tests to fulminant hepatic failure. Despite recent research efforts specific biomarkers are not still available for routine use in clinical practice, which makes the diagnosis of DILI uncertain and relying on a high degree of awareness of this condition and the exclusion of other causes of liver disease. Diagnostic scales such as the CIOMS/RUCAM can support the causality assessment of a DILI suspicion, but need refinement as some criteria are not evidence-based. Prospective collection of well-vetted DILI cases in established DILI registries has allowed the identification and validation of a number of clinical variables, and to predict a more severe DILI outcome. DILI is also in need of properly designed clinical trials to evaluate the efficacy of new DILI treatments as well as older drugs such as ursodeoxycholic acid traditionally used to ameliorate cholestasis or corticosteroids now widely tried in the oncology field to manage the emergent type of hepatotoxicity related to immune checkpoint inhibitors.

Valproic Acid-Induced Hyperammonemic Encephalopathy in a Patient with Bipolar Disorder: A Case Report

Valproic acid (VPA) is widely used to control various seizure disorders and psychiatric disorders. Valproic acid-induced hyperammonemic encephalopathy (VHE) is a rare but dangerous complication of VPA-induced toxicity. For this case report, several risk factors were identified, including young age, polytherapy regimens, VPA overdose, poor liver function, and carnitine deficiency. The detailed mechanisms of VHE remained unclear. Hyperammonemia may be caused by hypocarnitinemia, leading to imbalanced VPA metabolism. VHE may initially cause gastrointestinal symptoms, followed by a decreased level of consciousness and seizure. Early diagnosis of VHE is important for physicians for the timely reversal of VHE by discontinuing administration of VPA and administering lactulose or levocarnitine. Here, we describe a patient with a bipolar disorder who presented with VHE after receiving a strict vegetarian diet in our hospital. We recommend that VHE be included in the differential diagnosis of patients with high serum VPA levels and strictly vegetarian diets, especially those presenting with acute gastrointestinal symptoms.

Valproic Acid and the Liver Injury in Patients with Epilepsy: An Update

BACKGROUND

Valproic acid (VPA) as a widely used primary medication in the treatment of epilepsy is associated with reversible or irreversible hepatotoxicity. Long-term VPA therapy is also related to increased risk for the development of non-alcoholic fatty liver disease (NAFLD). In this review, metabolic elimination pathways of VPA in the liver and underlying mechanisms of VPA-induced hepatotoxicity are discussed.

METHODS

We searched in PubMed for manuscripts published in English, combining terms such as "Valproic acid", "hepatotoxicity", "liver injury", and "mechanisms". The data of screened papers were analyzed and summarized.

RESULTS

The formation of VPA reactive metabolites, inhibition of fatty acid β-oxidation, excessive oxidative stress and genetic variants of some enzymes, such as CPS1, POLG, GSTs, SOD2, UGTs and CYPs genes, have been reported to be associated with VPA hepatotoxicity. Furthermore, carnitine supplementation and antioxidants administration proved to be positive treatment strategies for VPA-induced hepatotoxicity.

CONCLUSION

Therapeutic drug monitoring (TDM) and routine liver biochemistry monitoring during VPA-therapy, as well as genotype screening for certain patients before VPA administration, could improve the safety profile of this antiepileptic drug.

Butyrate prevents valproate-induced liver injury: In vitro and in vivo evidence

Sodium valproate (VPA), an antiepileptic drug, may cause dose- and time-dependent hepatotoxicity. However, its iatrogenic molecular mechanism and the rescue therapy are disregarded. Recently, it has been demonstrated that sodium butyrate (NaB) reduces hepatic steatosis, improving respiratory capacity and mitochondrial dysfunction in obese mice. Here, we investigated the protective effect of NaB in counteracting VPA-induced hepatotoxicity using in vitro and in vivo models. Human HepG2 cells and primary rat hepatocytes were exposed to high VPA concentration and treated with NaB. Mitochondrial function, lipid metabolism, and oxidative stress were evaluated, using Seahorse analyzer, spectrophotometric, and biochemical determinations. Liver protection by NaB was also evaluated in VPA-treated epileptic WAG/Rij rats, receiving NaB for 6 months. NaB prevented VPA toxicity, limiting cell oxidative and mitochondrial damage (ROS, malondialdehyde, SOD activity, mitochondrial bioenergetics), and restoring fatty acid oxidation (peroxisome proliferator-activated receptor α expression and carnitine palmitoyl-transferase activity) in HepG2 cells, primary hepatocytes, and isolated mitochondria. In vivo, NaB confirmed its activity normalizing hepatic biomarkers, fatty acid metabolism, and reducing inflammation and fibrosis induced by VPA. These data support the protective potential of NaB on VPA-induced liver injury, indicating it as valid therapeutic approach in counteracting this common side effect due to VPA chronic treatment.

Levocarnitine for the Treatment of Valproic Acid-Induced Hyperammonemic Encephalopathy in Children: The Experience of a Large, Tertiary Care Pediatric Hospital and a Poison Center

BACKGROUND

Although rare, symptomatic hyperammonemia is sometimes associated with valproic acid (VPA), especially in children. L-carnitine (levocarnitine), sometimes classified as an essential amino acid, is vital to mitochondrial utilization of fatty acids and can be helpful in treating this condition. The data supporting this, however, are limited.

STUDY QUESTION

The aim of the study was to illustrate the role of L-carnitine in the treatment of patients with VPA-induced hyperammonemic encephalopathy (VPE) at 2 different institutions.

METHODS

Medical records of affected patients were reviewed; data collected included exposure history, clinical manifestations, physical examination, and laboratory values.

RESULTS

There were 13 cases of VPE; 12 were associated with therapeutic dosing and 1 with an overdose. The maximum ammonia concentration was 557 μmol/L, and blood concentrations of VPA ranged from 68 to 600 μg/mL (therapeutic range 50-100 μg/mL). In all cases, liver function tests were normal or only mildly increased. In this study, 12 patients received a daily dose of L-carnitine 100 mg/kg, and 1 received 200 mg/kg (intravenous infusion over 30 minutes) divided every 8 hours until clinical improvement. All patients made a full recovery. None developed adverse effects or reactions, and no cases of toxicity were reported.

CONCLUSION

Our series suggests that intravenous L-carnitine, at a dose of 100 mg·kg·d in 3 divided doses each over 30 minutes until clinical improvement occurs, is a safe and effective treatment in the management of VPE in children.

Rhabdomyolysis and Hepatotoxicity From Valproic Acid: Case Reports

Valproic acid (VPA) has been widely used more frequently as its approved indications have been expanded. More and more case reports on rare toxicities have been published in the literature (ie, hepatotoxicities, hyperammonemic encephalopathy, coagulation disorders, pancreatitis, thrombocytopenia). In spite of the long history of VPA, there is a lack of awareness of VPA toxicities among clinicians. We present two cases of a 44-year-old African American female and a 60-year-old Hispanic male taking chronic VPA therapy for psychiatric disorders admitted to the hospital with a combination of hepatotoxicities and acute kidney injury-associated rhabdomyolysis. In both cases, home VPA therapy was continued during hospitalization. Consequently, the female patient deceased and the male patient survived and discharged with continuation of his chronic VPA therapy. In cases of surviving patients, resumption of maintenance VPA upon discharge should be held and alternative therapy should be considered.

A Case Series of Severe Hyperammonemia Encephalopathy Related to Valproate: Can Antipsychotics Increase the Risk?

Valproate-induced hyperammonemia is a common side effect of valproate, which may occur either without any symptoms or may rarely cause symptoms of encephalopathy. Different risk factors have been defined for this side effect, including some nutritional deficiencies and polypharmacy (eg, other anticonvulsants). Three cases with psychiatric disorder who showed symptoms of severe hyperammonemia encephalopathy and had taken valproate with antipsychotics, especially risperidone, are presented here. In all cases, the symptoms were improved by discontinuation of valproate. Administration of antipsychotic may be considered as a risk factor for hyperammonemic encephalopathy related to valproate, specifically in some prone populations.

EASL Clinical Practice Guidelines: Drug-induced liver injury

Idiosyncratic (unpredictable) drug-induced liver injury is one of the most challenging liver disorders faced by hepatologists, because of the myriad of drugs used in clinical practice, available herbs and dietary supplements with hepatotoxic potential, the ability of the condition to present with a variety of clinical and pathological phenotypes and the current absence of specific biomarkers. This makes the diagnosis of drug-induced liver injury an uncertain process, requiring a high degree of awareness of the condition and the careful exclusion of alternative aetiologies of liver disease. Idiosyncratic hepatotoxicity can be severe, leading to a particularly serious variety of acute liver failure for which no effective therapy has yet been developed. These Clinical Practice Guidelines summarize the available evidence on risk factors, diagnosis, management and risk minimization strategies for drug-induced liver jury.

Determination of valproic acid and 3-heptanone in plasma using air-assisted liquid-liquid microextraction with the assistance of vortex: Application in the real samples

Introduction: Valproic acid (VPA) is an antiepileptic drug used to treat epilepsy and bipolar disorder. Adverse effects of VPA were studied in many reports, however, a dose-response relationship between VPA and its metabolites in epilepsy patients are extremely limited. In this paper, a high efficient method was developed for the preconcentration and determination of VPA and its main metabolite in plasma. Methods: For the extraction and preconcentration of the selected analytes, a volume of an extractant was placed at the bottom of the microtube containing pretreated plasma. The mixture was repeatedly withdrawn from the microtube and pushed-out into it using a 1.0-mL glass syringe and resulted in a cloudy mixture. For further turbidity, the mixture was shaken on a vortex agitator. This procedure was used to analyze the plasma samples of patients with epilepsy (n = 70). Results: The results revealed that in most patients with a low level of VPA relative to its expected level, 3-heptanone concentrations were high. The limits of quantification of 3-heptanone and VPA were 0.04 mg L-1 and 0.2 mg L-1, respectively. A suitable precision at a concentration of 2 mg L-1 for each analyte was obtained (relative standard deviation ≤ 9%). Conclusion: The obtained results indicated that this procedure is easy, sensitive, and reliable, and can be used for the analysis of the selected analytes in the plasma samples of patients with epilepsy.

Characterizing acyl-carnitine biosignatures for schizophrenia: a longitudinal pre- and post-treatment study

Subjects with schizophrenia have high risks of metabolic abnormalities and bioenergetic dysfunction. Acyl-carnitines involved in bioenergetic pathways provide potential biomarker targets for identifying early changes and onset characteristics in subjects with schizophrenia. We measured 29 acyl-carnitine levels within well-characterized plasma samples of adults with schizophrenia and healthy controls using liquid chromatography-mass spectrometry (LC-MS). Subjects with schizophrenia were measured at baseline and after 8 weeks of treatment. A total of 225 subjects with schizophrenia and 175 age- and gender-matched healthy controls were enrolled and 156 subjects completed the 8-week follow-up. With respect to plasma acyl-carnitines, the individuals with schizophrenia at baseline showed significantly higher levels of C4-OH (C3-DC) and C16:1, but lower concentrations of C3, C8, C10, C10:1, C10:2, C12, C14:1-OH, C14:2, and C14:2-OH when compared with healthy controls after controlling for age, sex, body mass index (BMI), smoking, and drinking. For the comparison between pretreatment and posttreatment subjects, all detected acyl-carnitines were significantly different between the two groups. Only the concentration of C3 and C4 were increased after selection by variable importance in projection (VIP) value >1.0 and false discovery rate (FDR) q value <0.05. A panel of acyl-carnitines were selected for the ability to differentiate subjects of schizophrenia at baseline from controls, pre- from post-treatment, and posttreatment from controls. Our data implicated acyl-carnitines with abnormalities in cellular bioenergetics of schizophrenia. Therefore, acyl-carnitines can be potential targets for future investigations into their roles in the pathoetiology of schizophrenia.

Adult Presentation of Ornithine Transcarbamylase Deficiency: 2 Illustrative Cases of Phenotypic Variability and Literature Review

Ornithine transcarbamylase (OTC) deficiency is an X-linked recessive disorder that usually presents in the neonatal period. Late-onset presentation of OTC can cause mild to severe symptoms. We describe laboratory and clinical findings of late-onset presentations of OTC deficiency. We conducted a literature search using search terms "ornithine transcarbamylase deficiency," "late onset presentation," and "hyperammonemia" from January 1, 1987, to December 31, 2016, was performed. Only papers published in English were included. We searched on PubMed, MEDLINE, and Google Scholar. We also present 2 OTC deficiency cases. A total of 30 adult cases had late-onset presentation of OTC deficiency reported. The majority were women (57%) with a median age of 37 years. The median level of ammonia was 308 mmol/L and the mortality rate was 30%. Our case 1 was a 40-year-old woman who succumbed to neurologic complications after a hyperammonemia crisis following an increased protein intake. Our case 2 was a 43-year-old woman with seizures associated with increased ammonia levels. Our 2 case reports show the wide phenotypic variability and severity in late-onset presentation of OTC ranging from seizures to cerebral herniation. Our literature review is the first to detail published laboratory and neurologic sequelae of late-onset OTC deficiency.