Effect of L-carnitine supplementation on acute valproate intoxication

Valproic Acid Overdose Review of a Case With Electrocardiographic Changes

BACKGROUND

Valproic acid (VPA) is increasingly used to treat a variety of medical disorders, such as seizures, psychiatric disorders, and headaches. Therefore, accidental and intentional ingestions with valproic acid are increasing.

OBJECTIVES

A case is presented in an adolescent with ischemic electrocardiographic changes after an acute overdose with VPA.

DISCUSSION

Major features of a valproic acid overdose include respiratory depression, progressive coma, hepatotoxicity, thrombocytopenia, and hemodynamic instability. Electrocardiographic abnormalities usually consist of tachycardia and nonspecific changes. Supportive care is indicated in most overdoses and involves the monitoring and correction of electrolyte abnormalities, coagulopathies, and acid-base imbalances. Treatment may include activated charcoal, naloxone, l-carnitine, and extracorporeal detoxification.

CONCLUSIONS

Valproic acid overdose is a relatively rare and electrocardiographic changes usually consist of tachycardia and nonspecific changes, but ischemic changes may occur and usually transient and require only recognition.

L-Carnitine supplementation to reverse hyperammonemia in a patient undergoing chronic valproic acid treatment: A case report

Valproic acid is a broad-spectrum anticonvulsant that has also gained attention in the psychiatric setting. With respect to safety, valproic acid may induce a seemingly rare condition, hyperammonemia, which can induce a wide variety of symptoms ranging from irritability to coma. The proposed mechanism of hyperammonemia involves depletion of carnitine and overproduction of a toxic metabolite, 4-en-valproic acid, both of which impair the urea cycle and thus ammonia elimination. Carnitine is a commonly used antidote for acute intoxication of valproic acid, but is not a therapeutic option for management of chronic adults with adverse effects related to valproic acid. We herein report a case involving a woman with epilepsy who developed hyperammonemia after a change in her anticonvulsant therapy. She reported increased seizures and gastrointestinal disturbances. Her ammonia, valproic acid, 4-en-valproic acid, and carnitine levels were monitored. Her ammonia level was elevated and her carnitine level was at the inferior limit of the population range. She was supplemented with carnitine at 1 g/day. After 1 month, her ammonia level decreased, her carnitine level increased, and her seizures were better controlled. Carnitine supplementation was useful for reversal of her hyperammonemia, allowing her to continue valproic acid for seizure control.

Antiepileptic drug poisoning: Three-year experience

INTRODUCTION

Antiepileptic drugs, which are also called anticonvulsants, are used in the therapy and prophylaxis of epileptic seizures. The purpose of this paper was to investigate the relevant epidemiological data and to determine which of these drugs was the most frequent cause of intoxication. Another purpose of this study was to determine the neurological, cardiac, and biochemical problems caused by antiepileptics.

MATERIAL AND METHOD

This retrospective study included 95 consecutive patients under 18 years of age with antiepileptic intoxication, presenting to and being followed-up in, the Toxicology Unit between January 2010 and February 2013. The data were obtained by screening the patient files.

RESULTS

Of the cases, 67 (70.5%) were self-poisoned by first generation antiepileptics (FGAEs) and 28 (29.5%) by second generation antiepileptics (SGAEs). The Glasgow Coma Scale (GCS) scores and the serum lactate levels of the patients poisoned by FGAEs and SGAEs on admission to emergency department were 15 (25th: 12; 75th: 15; 95th: 15; IQR: 3) and 1.9 (25th: 1.4; 75th: 3.1; 95th: 5.6; IQR: 1.7), and 15 (25th: 14.3; 75th: 15; 95th: 15; IQR: 0.75) and 1.07 (25th: 0.9; 75th: 1.6; 95th: 5.5; IQR: 0.71), respectively. The serum lactate levels of patients poisoned by FGAEs were significantly higher (p < 0.001). Among the cases poisoned by carbamazepine, the most frequent cause of intoxication, the GCS score was significantly lower and serum lactate level was significantly higher in the group with high serum levels of carbamazepine (p = 0.004 and p < 0.001, respectively). In cases poisoned by valproic acid (VPA), the second frequent cause of intoxication, there was neither a significant association between the serum VPA level and the GCS score, nor between the serum lactate level and the systolic blood pressure (p = 0.470, p = 0.897, and p = 0.088, respectively). However, there was a positive correlation between the serum VPA level and the serum ammonia level (kk = 0.742, p < 0.001).

CONCLUSION

First generation antiepileptics are more toxic than SGAEs. In patients with serum carbamazepine level, particularly those over 30 mg/L, serious disorders of consciousness, cardiovascular toxicity, and metabolic disorders may occur. In VPA intoxication, there is a positive correlation between the serum VPA levels and ammonia levels. On account of this finding, one should be more careful about hyperammonemic hepatic encephalopathy as the serum VPA level rises.

Hepatic toxicity of dronedarone in mice: role of mitochondrial β-oxidation

Dronedarone is an amiodarone-like antiarrhythmic drug associated with severe liver injury. Since dronedarone inhibits mitochondrial respiration and β-oxidation in vitro, mitochondrial toxicity may also explain dronedarone-associated hepatotoxicity in vivo. We therefore studied hepatotoxicity of dronedarone (200mg/kg/day for 2 weeks or 400mg/kg/day for 1 week by intragastric gavage) in heterozygous juvenile visceral steatosis (jvs(+/-)) and wild-type mice. Jvs(+/-) mice have reduced carnitine stores and are sensitive for mitochondrial β-oxidation inhibitors. Treatment with dronedarone 200mg/kg/day had no effect on body weight, serum transaminases and bilirubin, and hepatic mitochondrial function in both wild-type and jvs(+/-) mice. In contrast, dronedarone 400mg/kg/day was associated with a 10-15% drop in body weight, and a 3-5-fold increase in transaminases and bilirubin in wild-type mice and, more accentuated, in jvs(+/-) mice. In vivo metabolism of intraperitoneal (14)C-palmitate was impaired in wild-type, and, more accentuated, in jvs(+/-) mice treated with 400mg/kg/day dronedarone compared to vehicle-treated mice. Impaired β-oxidation was also found in isolated mitochondria ex vivo. A likely explanation for these findings was a reduced activity of carnitine palmitoyltransferase 1a in liver mitochondria from dronedarone-treated mice. In contrast, dronedarone did not affect the activity of the respiratory chain ex vivo. We conclude that dronedarone inhibits mitochondrial β-oxidation in and ex vivo, but not the respiratory chain. Jvs(+/-) mice are slightly more sensitive for the effect of dronedarone on mitochondrial β-oxidation than wild-type mice. The results suggest that inhibition of mitochondrial β-oxidation is an important mechanism of hepatotoxicity associated with dronedarone.

Nutrition as medical therapy

Recent data support the use of nutritional agents for use as targeted medical therapy. This article reviews some of the pharmacologic roles that parenteral nutritional ingredients (selenium, lipid emulsion, insulin, and levocarnitine) can play in the setting of critical illness.

Carnitine and acylcarnitines: pharmacokinetic, pharmacological and clinical aspects

L-Carnitine (levocarnitine) is a naturally occurring compound found in all mammalian species. The most important biological function of L-carnitine is in the transport of fatty acids into the mitochondria for subsequent β-oxidation, a process which results in the esterification of L-carnitine to form acylcarnitine derivatives. As such, the endogenous carnitine pool is comprised of L-carnitine and various short-, medium- and long-chain acylcarnitines. The physiological importance of L-carnitine and its obligatory role in the mitochondrial metabolism of fatty acids has been clearly established; however, more recently, additional functions of the carnitine system have been described, including the removal of excess acyl groups from the body and the modulation of intracellular coenzyme A (CoA) homeostasis. In light of this, acylcarnitines cannot simply be considered by-products of the enzymatic carnitine transfer system, but provide indirect evidence of altered mitochondrial metabolism. Consequently, examination of the contribution of L-carnitine and acylcarnitines to the endogenous carnitine pool (i.e. carnitine pool composition) is critical in order to adequately characterize metabolic status. The concentrations of L-carnitine and its esters are maintained within relatively narrow limits for normal biological functioning in their pivotal roles in fatty acid oxidation and maintenance of free CoA availability. The homeostasis of carnitine is multifaceted with concentrations achieved and maintained by a combination of oral absorption, de novo biosynthesis, carrier-mediated distribution into tissues and extensive, but saturable, renal tubular reabsorption. Various disorders of carnitine insufficiency have been described but ultimately all result in impaired entry of fatty acids into the mitochondria and consequently disturbed lipid oxidation. Given the sensitivity of acylcarnitine concentrations and the relative carnitine pool composition in reflecting the intramitochondrial acyl-CoA to free CoA ratio (and, hence, any disturbances in mitochondrial metabolism), the relative contribution of L-carnitine and acylcarnitines within the total carnitine pool is therefore considered critical in the identification of mitochondria dysfunction. Although there is considerable research in the literature focused on disorders of carnitine insufficiency, relatively few have examined relative carnitine pool composition in these conditions; consequently, the complexity of these disorders may not be fully understood. Similarly, although important studies have been conducted establishing the pharmacokinetics of exogenous carnitine and short-chain carnitine esters in healthy volunteers, few studies have examined carnitine pharmacokinetics in patient groups. Furthermore, the impact of L-carnitine administration on the kinetics of acylcarnitines has not been established. Given the importance of L-carnitine as well as acylcarnitines in maintaining normal mitochondrial function, this review seeks to examine previous research associated with the homeostasis and pharmacokinetics of L-carnitine and its esters, and highlight potential areas of future research.

Unilateral basal-ganglia involvement likely due to valproate-induced hyperammonemic encephalopathy

A male child suffering from generalized tonic clonic epilepsy, on treatment with valproate, developed fulminant hepatic failure, hyperammonemia and encephalopathy due to drug toxicity. The most extraordinary feature was his MRI (FLAIR image) of brain which showed unilateral hyperintensities in right putamen and caudate nucleus. The patient recovered on withdrawal of valproate with mild residual left sided athetotic movements during remission. Repeat investigation confirmed an improved MRI imaging and normalised blood ammonia levels. The case report is unique because of unilateral involvement of basal ganglia due to valproate-induced encephalopathy.

[Relationship between plasma concentrations of valproic acid and hepatotoxicity in patients receiving high doses]

INTRODUCTION

Valproic acid (VPA) is an anticonvulsivant drug widely prescribed in the treatment of many forms of generalized epilepsy. In literature, the incidence of liver damage induced by AVP is 0.01%. It is potentialized by the combination therapy (phenobarbital, carbamazepine). Severe hepatotoxicity is rare and appears to be independent of dose and to cause a high mortality.

METHODS

The aim of our study was to evaluate the relationship between plasma concentrations of AVP and the occurrence of side effects especially hepatotoxicity in patients receiving high doses of AVP.

RESULTS

In this period, 425 plasmatic AVP monitoring were carried out in our laboratory. From 128 patients treated by high doses of AVP, only 73 were included in this study. Our work showed that adverse effects in epileptics under high doses of AVP was related to the association of the AVP with other antiepileptic in particular carbamazépine, phenobarbital and benzodiazepines rather than supra-therapeutic plasmatic concentrations of AVP. The association of AVP to major antiepileptics (carbamazépine and or phenobarbital) does not seem to generate an increase in the plasmatic concentration of AVP, which was not associated with a greater risque of adverse effects.

CONCLUSION

Consequently, clinical signs of liver toxicity may be present in AVP concentrations generally considered in the therapeutic range especially when used in high doses and or combined with antiepileptic drugs like phenobarbital or carbamazepine.

Oral valproic acid for epilepsy--long-term experience in therapy and side effects

Valproic acid (VPA) is considered to be a drug of first choice and one of the most frequently-prescribed antiepileptic drugs worldwide for the therapy of generalized and focal epilepsies, including special epileptic. It is a broad-spectrum antiepileptic drug and is usually well tolerated. Rarely, serious complications may occur in some patients, including hemorrhagic pancreatitis, coagulopathies, bone marrow suppression, VPA-induced hepatotoxicity and encephalopathy, but there is still a lack of knowledge about the incidence and occurrence of these special side effects. Additionally, the consequences for VPA therapy and indication are more or less unclear. By literature review and own data this review addresses some of the challenges of VPA therapy and its side effects, which are not unique to epilepsy in childhood.

Neurointensive care management of raised intracranial pressure caused by severe valproic acid intoxication

INTRODUCTION

We describe the neurointensive care (NIC) management of a patient with severe cerebral swelling and raised intracranial pressure (ICP) after severe sodium valproic acid (VPA) intoxication. A previously healthy 25-year old male with mild tonic-clonic epilepsy was found unconscious with serum VPA levels >10,000 micromol/l. The patient deteriorated to Glasgow Motor Scale score (GMS) 2 and a CT scan showed signs of raised ICP. Early ICP was elevated, >50 mm Hg, and continuous EEG monitoring showed isoelectric readings.

METHODS

The patient was treated with an ICP-guided protocol including mild hyperventilation, normovolemia, head elevation and intermittent doses of mannitol. Due to refractory elevations of ICP, high-dose pentobarbital infusion was initiated, and ICP gradually normalised.

RESULTS

There were several systemic complications including coagulopathy, hypocalcemia and pancreatitis. The patient remained in a depressed level of consciousness for 2 months but gradually recovered, showing a good recovery with minor subjective cognitive deficits by 6 months.

CONCLUSION

We conclude that NIC may be an important treatment option in cases of severe intoxication causing cerebral swelling.

Fatal valproate overdose in a newborn baby

Valproate is a widely used drug in the treatment of epilepsy in children and adults. However, it is not safe for patients under two years of age, especially during the newborn period. This study presents a case of fatal valproate overdose in a 26-day-old female newborn, who is the youngest patient in the literature.

Carnitine as an antidote for acute valproate toxicity in children

PURPOSE OF REVIEW

Valproic acid is a widely used anticonvulsant that has recently been approved for stabilization of manic episodes in patients with bipolar disorder. As the use of valproic acid increases, the number of both accidental and intentional exposures increases. This is paralleled by more reports of valproic-acid-induced toxicity. The purpose of this article is to review the pathophysiology and toxicology of valproic acid and determine whether the literature supports the use of carnitine as a treatment for acute valproic-acid-induced toxicity.

RECENT FINDINGS

Recent literature documents no cases of allergic reactions or serious side effects associated with the administration of carnitine when given patients with acute ingestions of valproic acid. Other findings suggest that carnitine increases the survival rate of patients who develop valproic-acid-induced hepatotoxicity. Early intervention with intravenous rather than enteral L-carnitine was associated with the greatest hepatic survival. Isolated pediatric case reports show that carnitine administration may reverse toxic metabolic pathways but may not hasten clinical improvement.

SUMMARY

Based on this recent literature, it seems reasonable to use carnitine for documented severe valproic acid toxicity, particularly in cases where patients present with coma, rising ammonia level, or valproic acid levels greater than 450 mg/l.

Valproic Acid-induced Hepatopathy: Nine New Fatalities in Germany from 1994 to 2003

PURPOSE

Valproic acid (VPA) is an antiepileptic drug (AED) commonly used for generalized and focal epilepsies. We provide an update on hepatotoxic side effects in Germany between 1994 and 2003.

METHODS

We mailed a questionnaire to all members of the German Section of the International League Against Epilepsy, asking for VPA-induced side effects, especially severe side effects such as hepatopathy.

RESULTS

As a result of our questionnaire, we found 31 cases of reversible hepatotoxicity and nine cases of lethal hepatopathies in Germany from 1994 to 2003.

CONCLUSIONS

The outcome of patients with severe hepatotoxicity is better than that in the past. The risk of a VPA-induced hepatopathy is not limited to patients younger than 2 years, receiving polytherapy, or patients with congenital or acquired metabolic diseases.

Differentiating the causes of metabolic acidosis in the poisoned patient

Numerous drugs and toxins may induce the development of a metabolic acidosis. The treating physician should be cognizant of the many compounds that can produce metabolic acidosis following an overdose or an accidental exposure, or with therapeutic use. Knowledge and comprehension of the substances associated with metabolic acidosis will facilitate the diagnosis and treatment of poisoned patients.

Metabolic acidosis: differentiating the causes in the poisoned patient

Metabolic acidosis may arise from several drugs and toxins through a variety of mechanisms. Differentiating the causes of metabolic acidosis in the poisoned patient is an indispensable skill in clinical practice. Comprehension of toxin-induced metabolic acidosis, combined with a thorough history, physical examination, appropriate use of laboratory tests, and a stepwise approach, should aid the clinician in determining the cause of metabolic acidosis in the poisoned patient. When confronted with such a patient, it is imperative that one administer appropriate antidotal therapy, when necessary, and provide the patient with exceptional supportive care.

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

Valproic acid (VPA) is a broad-spectrum antiepileptic drug and is usually well tolerated, but rare serious complications may occur in some patients receiving VPA chronically, including haemorrhagic pancreatitis, bone marrow suppression, VPA-induced hepatotoxicity (VHT) and VPA-induced hyperammonaemic encephalopathy (VHE). Some data suggest that VHT and VHE may be promoted by carnitine deficiency. Acute VPA intoxication also occurs as a consequence of intentional or accidental overdose and its incidence is increasing, because of use of VPA in psychiatric disorders. Although it usually results in mild central nervous system depression, serious toxicity and even fatal cases have been reported. Several studies or isolated clinical observations have suggested the potential value of oral L-carnitine in reversing carnitine deficiency or preventing its development as well as some adverse effects due to VPA. Carnitine supplementation during VPA therapy in high-risk patients is now recommended by some scientific committees and textbooks, especially paediatricians. L-carnitine therapy could also be valuable in those patients who develop VHT or VHE. A few isolated observations also suggest that L-carnitine may be useful in patients with coma or in preventing hepatic dysfunction after acute VPA overdose. However, these issues deserve further investigation in controlled, randomized and probably multicentre trials to evaluate the clinical value and the appropriate dosage of L-carnitine in each of these conditions.

l-carnitine was safely administered in the setting of valproate toxicity

BACKGROUND

L-Carnitine is a carnitine replacement that has been used in carnitine deficiency states. We conducted a review of patients with acute valproate (VPA) poisoning that had an elevated ammonia level and received L-carnitine to address safety.

METHODS

After a brief training of systematic chart review, reviewers blinded to the purpose of the study completed a standardized data collection sheet. Ages, outcomes, side effects, presence of hyperammonemia, and total carnitine doses were recorded.

RESULTS

Three years of poison center charts from more than 300,000 patients were reviewed; 674 patients ingested valproic acid. The median age was 26.2 years (range, 1-58 years). L-Carnitine was routinely recommended if the ammonia level was elevated. Fifty-five doses of carnitine were administered to 19 patients who had isolated VPA ingestions and 196 doses of carnitine were administered to patients with mixed overdoses that included VPA, all with an elevated ammonia level. No patient had a documented allergic reaction or side effects.

CONCLUSIONS

Two hundred fifty-one L-carnitine doses were not associated with adverse or toxic effects in our VPA toxic patients.

Valproic Acid—Induced Hyperammonemia and Thrombocytopenia in an Elderly Woman

OBJECTIVE

To describe a case of oral valproic acid—induced hyperammonemia and thrombocytopenia in an elderly patient.

CASE SUMMARY

A 76-year-old white woman presented to the emergency department with generalized weakness, confusion, nausea, and vomiting. She was taking sodium divalproex 750 mg 3 times daily, with valproic acid concentration 144 mg/L. She was admitted to the medical ward. The dose of sodium divalproex was decreased and discontinued. During her hospital stay, the woman's ammonia level rose to 211 μg/dL despite a normal valproic acid concentration. She was confused, somnolent, and had decreased mobility. Her platelet count decreased from 133 to 86 × 103/mm 3 . Gabapentin was prescribed for seizure control. The patient's mental status, ammonia level, and platelet count returned to baseline following discontinuation of valproic acid.

DISCUSSION

It has been reported that valproic acid can interfere with the enzyme carbamoylphosphate synthetase, which is responsible for incorporating ammonia into the urea cycle. It has also been reported that valproic acid can increase the transport of glutamine across the mitochondrial membrane in the kidney, thereby increasing the production of ammonia. The etiology of valproic acid—induced thrombocytopenia has not been elucidated. Using the Naranjo probability scale, a probable relationship between hyperammonemia and valproic acid and a possible relationship between thrombocytopenia and valproic acid were determined.

CONCLUSIONS

Valproic acid can be associated with hyperammonemia and thrombocytopenia. Clinicians should be aware of changes in patients' cognitive and functional capacity, especially elderly patients on sodium divalproex.

Épuration extrarénale, supplémentation en L-carnitine et intoxication à l’acide valproïque

We report the case of a severe valproic acid poisoning in a 36-year-old man. In front of a high serum concentration of valproic acid at the admission, haemodialysis was initiated to decrease serum valproic acid concentration. A L-carnitine therapy (50 mg/kg per day) was also started. A cerebral oedema appeared at the third day, but the patient recovered without any sequela.

Pharmacokinetics of L-carnitine

L-Carnitine is a naturally occurring compound that facilitates the transport of fatty acids into mitochondria for beta-oxidation. Exogenous L-carnitine is used clinically for the treatment of carnitine deficiency disorders and a range of other conditions. In humans, the endogenous carnitine pool, which comprises free L-carnitine and a range of short-, medium- and long-chain esters, is maintained by absorption of L-carnitine from dietary sources, biosynthesis within the body and extensive renal tubular reabsorption from glomerular filtrate. In addition, carrier-mediated transport ensures high tissue-to-plasma concentration ratios in tissues that depend critically on fatty acid oxidation. The absorption of L-carnitine after oral administration occurs partly via carrier-mediated transport and partly by passive diffusion. After oral doses of 1-6g, the absolute bioavailability is 5-18%. In contrast, the bioavailability of dietary L-carnitine may be as high as 75%. Therefore, pharmacological or supplemental doses of L-carnitine are absorbed less efficiently than the relatively smaller amounts present within a normal diet.L-Carnitine and its short-chain esters do not bind to plasma proteins and, although blood cells contain L-carnitine, the rate of distribution between erythrocytes and plasma is extremely slow in whole blood. After intravenous administration, the initial distribution volume of L-carnitine is typically about 0.2-0.3 L/kg, which corresponds to extracellular fluid volume. There are at least three distinct pharmacokinetic compartments for L-carnitine, with the slowest equilibrating pool comprising skeletal and cardiac muscle.L-Carnitine is eliminated from the body mainly via urinary excretion. Under baseline conditions, the renal clearance of L-carnitine (1-3 mL/min) is substantially less than glomerular filtration rate (GFR), indicating extensive (98-99%) tubular reabsorption. The threshold concentration for tubular reabsorption (above which the fractional reabsorption begins to decline) is about 40-60 micromol/L, which is similar to the endogenous plasma L-carnitine level. Therefore, the renal clearance of L-carnitine increases after exogenous administration, approaching GFR after high intravenous doses. Patients with primary carnitine deficiency display alterations in the renal handling of L-carnitine and/or the transport of the compound into muscle tissue. Similarly, many forms of secondary carnitine deficiency, including some drug-induced disorders, arise from impaired renal tubular reabsorption. Patients with end-stage renal disease undergoing dialysis can develop a secondary carnitine deficiency due to the unrestricted loss of L-carnitine through the dialyser, and L-carnitine has been used for treatment of some patients during long-term haemodialysis. Recent studies have started to shed light on the pharmacokinetics of L-carnitine when used in haemodialysis patients.

Valproic acid toxicity: overview and management

Acute valproic acid intoxication is an increasing problem, accounting for more than 5000 calls to the American Association of Poison Control Centers in 2000. The purpose of this paper is to review the pharmacology and toxicology of valproic acid toxicity. Unlike earlier antiepileptic agents, valproic acid appears to function neither through sodium channel inhibition nor through direct gamma-aminobutyric acid agonism, but through an indirect increase in regional brain gamma-aminobutyric acid levels. Manifestations of acute valproic acid toxicity are myriad, and reflect both exaggerated therapeutic effect and impaired intermediary metabolism. Central nervous system depression is the most common finding noted in overdose, and may progress to coma and respiratory depression. Cerebral edema has also been observed. Although hepatotoxicity is rare in the acute overdose setting, pancreatitis and hyperammonemia have been reported. Metabolic and hematologic derangements have also been described. Management of acute valproic acid ingestion requires supportive care and close attention to the airway. The use of controversial adjunctive therapies, including extracorporeal drug elimination and L-carnitine supplementation, will be discussed.

Hyperammonemia and coma without hepatic dysfunction induced by valproate therapy

The authors report a case of a 41-year-old mentally disabled man with bipolar disorder who presented to the emergency department with altered mental status. He was found to have a significantly elevated ammonia level (377 microM/L) with no signs of hepatic insufficiency. His coma and hyperammonemia were attributed to his chronic valproate therapy. This patient had the highest serum ammonia level ever reported with a therapeutic valproate level in the absence of any other anticonvulsant therapy, metabolic abnormality, or hepatic dysfunction. The authors discuss this case and review the current literature on hyperammonemia in valproic acid therapy and the use of L-carnitine in these patients.

Valproic acid intoxication identified by 1H and 1H-(13)C correlated NMR spectroscopy of urine samples

Analysis of biological fluids by proton and carbon nuclear magnetic resonance spectroscopy (1H and 13C NMR) is a promising tool in clinical biology. We used this method for rapid toxicological screening in the case of two suicide attempts. For each case, a urine sample was analysed at 300 MHz by 1D and 2D sequences (TOCSY and HMBC) in a short experimental time. Quantification was performed by peak integration on the 1D 1H NMR spectrum. For the two patients, results showed the same resonances of the major metabolite, valproyl-O-glucuronide at concentrations of 121 and 44 mmol/l.

The role of carnitine supplementation during valproic acid therapy

OBJECTIVE

To review the pathophysiology and significance of valproic acid-induced carnitine deficiency; to present and evaluate the literature pertaining to carnitine supplementation in pediatric patients receiving valproic acid; and to present the consensus guidelines for carnitine supplementation during valproic acid therapy.

DATA SOURCES

A MEDLINE search (1966-December 1998) restricted to English-language literature, using MeSH headings of carnitine and valproic acid, was conducted to identify clinically relevant articles. Selected articles and references focusing on the pediatric population were included for review.

DATA EXTRACTION

Study design, patient population, methods, and clinical outcomes were evaluated.

DATA SYNTHESIS

Valproic acid, a widely used antiepileptic agent in the pediatric population, is limited by a 1/800 incidence of fatal hepatotoxicity in children under the age of two years. Carnitine is an essential amino acid necessary in beta-oxidation of fatty acids and energy production in cellular mitochondria. It has been hypothesized that valproic acid may induce a carnitine deficiency in children and cause nonspecific symptoms of deficiency, hepatotoxicity, and hyperammonemia. Relevant published case reports and trials studying this relationship are evaluated, and a consensus statement by the Pediatric Neurology Advisory Committee is reviewed.

CONCLUSIONS

Despite the lack of prospective, randomized clinical trials documenting efficacy of carnitine supplementation in preventing valproic acid-induced hepatotoxicity, the few limited studies available have shown carnitine supplementation to result in subjective and objective improvements along with increases in carnitine serum concentrations in patients receiving valproic acid. The Pediatric Neurology Advisory Committee in 1996 provided more concrete indications on the role of carnitine in valproic acid therapy, such as valproic acid overdose and valproic acid-induced hepatotoxicity. Carnitine was strongly recommended for children at risk of developing a carnitine deficiency. Although carnitine has been well tolerated, future studies are needed to evaluate the efficacy of prophylactic carnitine supplementation for the prevention of hepatotoxicity.