Renal toxicity induced by valproic acid (Depakene)

Kidney tubular injury induced by valproic acid: systematic literature review

BACKGROUND

Valproic acid is prescribed for epilepsy and as prophylaxis for bipolar disorder and migraine headaches. It has also been implicated as a cause of a kidney tubular injury.

METHODS

We undertook a review of the literature to characterize the biochemical and histopathological features of the overt kidney tubular injury and to evaluate the possible existence of a pauci-symptomatic injury. The pre-registered review (CRD42022360357) was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. Searches were conducted in Excerpta Medica, the National Library of Medicine, and Web of Science. The gray literature was also considered.

RESULTS

For the final analysis, we retained 36 articles: 28 case reports documented 48 individuals with epilepsy on valproic acid for 7 months or more and presenting with features consistent with an overt kidney tubular injury. The following disturbances were noted: hypophosphatemia (N = 46), normoglycemic glycosuria (N = 46), total proteinuria (N = 45), metabolic acidosis (N = 36), hypouricemia (N = 27), tubular proteinuria (N = 27), hypokalemia (N = 23), and hypocalcemia (N = 8). A biopsy, obtained in six cases, disclosed altered proximal tubular cells with giant and dysmorphic mitochondria. Eight case series addressed the existence of a pauci- or even asymptomatic kidney injury. In the reported 285 subjects on valproic acid for 7 months or more, an isolated tubular proteinuria, mostly N-acetyl-β-glucosaminidase, was often noted.

CONCLUSIONS

Valproic acid may induce an overt kidney tubular injury, which is associated with a proximal tubular mitochondrial toxicity. Treatment for 7 months or more is often associated with a pauci- or oligosymptomatic kidney tubular injury. A higher resolution version of the Graphical abstract is available as Supplementary information.

Valproic-induced Fanconi syndrome: Clinical features, risk factors, diagnosis and management

Objective

Although Fanconi syndrome (FS) induced by valproate (VPA) has occasionally been reported, the detailed clinical features of the disease remain unclear. The aim of this study was to elucidate the clinical features of patients with VPA-induced FS.

Methods

We searched Chinese and English databases for all original studies, clinical reports, and case reports on VPA-induced FS published before March 2022.

Results

A total of 29 articles including 54 patients (28 males and 24 females) were included. The patients had a median age of 7 years (range 2–34 years), had severely disabled (87.0%), tube feeding (64.8%), and received an average of 1.8 medications other than VPA. The median duration of VPA treatment was 4 years (range 0.7–15.5). Pathological fractures (25.9%), unexplained fever (11.1%), muscle weakness (9.3%), and edema (9.3%) were the most common symptoms, while 18 patients were diagnosed in incidental laboratory tests. Blood tests revealed hypokalemia (69.2%), hypophosphatemia (98.0%), and hypouricemia (93.3%). Urinalysis revealed glucosuria (96.1%), proteinuria (100.0%), generalized hyperaminoaciduria (100.0 %), β2 macroglobulin (100.0%). Decreased percent total reabsorption of phosphate (%TRP) found in 94.1% of patients, and increased fractional excretion of uric acid (FEUA) were found in 100% of patients. The median time to resolution of FS after discontinuation of drug therapy was 3 months (range 0.25–18).

Conclusions

The possibility of FS needs to be considered with long-term VPA administration, especially in young, tube-fed, severely disabled patients who are co-administered with anticonvulsants. Patients receiving VPA should have regular blood and urine tests. Abnormal laboratory values returned to normal levels after VPA discontinuation.

Managing the patient with epilepsy and renal impairment

PURPOSE

Epilepsy affects more than 50 million people worldwide and its management can be complicated by comorbidities such as impaired renal function. To optimize epilepsy control in patients with kidney disease, clinicians need to be aware of how antiepileptic drugs (AEDs) are affected by impaired renal function and how the kidneys are affected by epilepsy management strategies. Herein we present a narrative review with systematic literature search to discuss the use of AEDs in patients with renal impairment, including those undergoing dialysis, as well as the nephrotoxic effects of some AEDs. We finally conclude the article by providing practical tips about our approach to using AEDs in the setting of renal disease.

METHODS

A literature search targeting epilepsy management in patients with kidney disease was performed in MEDLINE database (1946 to 7th Jan 2019).

RESULTS

A total of 1193 articles were found. After duplicate removal, title and abstract screening followed by full text screening, a total of 110 references were included in this review. Additional information was included from drug product monographs.

CONCLUSION

The disposition of AEDs can be altered in patients with impaired renal function, leading to a higher risk of AED toxicity or therapy failure. Renal dosage adjustment and close monitoring is recommended. Although AED-induced nephrotoxicity is rare, it is unpredictable and clinicians need to vigilant about this possibility. In addition, AEDs renal adverse reactions and renal drug interactions should be considered when selecting an AED.

Proximal renal tubular acidosis with and without Fanconi syndrome

Proximal renal tubular acidosis (RTA) is caused by a defect in bicarbonate (HCO₃⁻) reabsorption in the kidney proximal convoluted tubule. It usually manifests as normal anion-gap metabolic acidosis due to HCO₃⁻ wastage. In a normal kidney, the thick ascending limb of Henle’s loop and more distal nephron segments reclaim all of the HCO₃⁻ not absorbed by the proximal tubule. Bicarbonate wastage seen in type II RTA indicates that the proximal tubular defect is severe enough to overwhelm the capacity for HCO₃⁻ reabsorption beyond the proximal tubule. Proximal RTA can occur as an isolated syndrome or with other impairments in proximal tubular functions under the spectrum of Fanconi syndrome. Fanconi syndrome, which is characterized by a defect in proximal tubular reabsorption of glucose, amino acids, uric acid, phosphate, and HCO₃⁻, can occur due to inherited or acquired causes. Primary inherited Fanconi syndrome is caused by a mutation in the sodium-phosphate cotransporter (NaP_i-II) in the proximal tubule. Recent studies have identified new causes of Fanconi syndrome due to mutations in the EHHADH and the HNF4A genes. Fanconi syndrome can also be one of many manifestations of various inherited systemic diseases, such as cystinosis. Many of the acquired causes of Fanconi syndrome with or without proximal RTA are drug-induced, with the list of causative agents increasing as newer drugs are introduced for clinical use, mainly in the oncology field.

Kidney Biopsy Findings in a Patient With Valproic Acid-Associated Fanconi Syndrome

A 7-year-old boy with a history of febrile illness-related epilepsy syndrome presented with proteinuria and elevated creatinine. His severe epileptic disorder has been treated since age 2 with multiple antiepileptic medications, including valproic acid. More recently, he was noted to have features of Fanconi syndrome with acidosis, hypophosphatemia, hypokalemia, glucosuria, and nephrotic-range proteinuria. This was managed with supplements; however, in the setting of rising creatinine and prominent proteinuria, a kidney biopsy was performed. Renal cortex revealed markedly decreased expression of proximal tubule markers and increased expression of markers of distal nephron differentiation. Such findings have been described in several genetic and acquired conditions, including renal tubular dysgenesis, severe hypoxic injury following renal artery stenosis, and toxic injury related to in utero exposure to angiotensin-converting-enzyme inhibitors. Such changes have not been reported before in valproic acid-associated Fanconi syndrome, although in general, morphologic findings in this condition have not been well established in the literature.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

Mechanism of valproic acid-induced Fanconi syndrome involves mitochondrial dysfunction and oxidative stress in rat kidney

AIM

Drug-induced kidney proximal tubular injury and renal failure (Fanconi syndrome; FS) is a clinical complication. Valproic acid (VPA) is among the FS-inducing drugs. The current investigation was designed to evaluate the role of mitochondrial dysfunction and oxidative stress in VPA-induced renal injury.

METHODS

Animals received VPA (250 and 500 mg/kg, i.p., 15 consecutive days). Serum biomarkers of kidney injury and markers of oxidative stress were assessed. Moreover, kidney mitochondria were isolated and mitochondrial indices, including succinate dehydrogenase activity (SDA), mitochondrial depolarization, mitochondrial permeability transition pore (MPP), reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial glutathione, and ATP were determined.

RESULTS

Valproic acid-treated animals developed biochemical evidence of FS as judged by elevated serum gamma-glutamyl transferase (γ-GT), alkaline phosphatase (ALP), creatinine (Cr), and blood urea nitrogen (BUN) along with hypokalaemia, hypophosphataemia, and a decrease in serum uric acid. VPA caused an increase in kidney ROS and LPO. Renal GSH reservoirs were depleted and tissue antioxidant capacity decreased in VPA-treated animals. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were also evident in VPA-treated rats. Mitochondrial parameters including SDA, MMP, GSH, ATP and MPP were decreased and mitochondrial ROS and LPO were increased with VPA treatment. It was found that carnitine (100 mg/kg, i.p.) mitigated VPA adverse effects towards the kidney.

CONCLUSIONS

These data suggest that mitochondrial dysfunction and oxidative stress contributed to the VPA-induced FS. On the other hand, carnitine could be considered a potentially safe and effective therapeutic option in attenuating VPA-induced renal injury.

Decreased bone density induced by antiepileptic drugs can cause accelerated orthodontic tooth movement in male Wistar rats

PURPOSE

The aim of the present study was to evaluate the effect of the carbamazepine and valproic acid on orthodontic tooth movement in male Wistar rats.

METHODS

Evaluation of tooth movement after 21 days of drugs infusion was carried out by feeler gauge. Bone densitometry on lateral cephalograms was conducted on days 1 and 21. After dissection of the maxillae, histologic parameters were evaluated.

RESULTS

Orthodontic tooth movement was accelerated in experimental groups rather than controls. Optical density was significantly increased in these groups. In histologic sections, mesioapical portion of the PDL (Periodontal Ligament) was wider in experimental groups. Also, distoapical portion of the PDL was wider only in valproic acid group.

CONCLUSION

Valproic acid and carbamazepine can decrease the bone density which may induce the accelerated orthodontic tooth movement in rats.

Outcome of renal proximal tubular dysfunction with Fanconi syndrome caused by sodium valproate

BACKGROUND

Although Fanconi syndrome is rare in patients with epilepsy treated with sodium valproate (VPA), the prevalence might be higher in children with severe motor and intellectual disabilities (SMID). VPA-induced Fanconi syndrome usually has a favorable outcome, but the long-term outcome of renal tubular dysfunction in SMID patients remains unknown. The aim of this study was therefore to investigate the long-term outcome of renal proximal dysfunction in SMID children with Fanconi syndrome caused by VPA.

METHODS

The records of six children with SMID and Fanconi syndrome caused by VPA were retrospectively reviewed to assess long-term proximal renal tubular function after discontinuation of VPA. All six patients had intractable epilepsy and required tube feeding.

RESULTS

Proximal tubular dysfunction improved in almost all patients after VPA discontinuation, although abnormal uric acid reabsorption persisted in three patients. Five patients had hypocarnitinemia. After carnitine supplementation, one of these three patients with decreased ability to reabsorb uric acid had a normal serum level and improved fractional excretion of uric acid.

CONCLUSIONS

Secondary carnitine deficiency may cause prolonged tubular dysfunction in some SMID patients with VPA-induced Fanconi syndrome. Fanconi syndrome caused by VPA is a usually reversible dysfunction of the proximal tubules, but can be permanent. Although not effective for all patients, carnitine is recommended for patients with VPA-induced Fanconi syndrome, especially children with SMID.

Sodium valproate-induced Fanconi type proximal renal tubular acidosis

We present a case series of three patients with sodium valproate-induced Fanconi's syndrome, with ages ranging from 5 years to 12 years. The most important diagnostic features of this syndrome include hypophosphataemia, glycosuria and proteinuria, which are also noted in our series. Furthermore, also added is that clinical fractures representing an underlying osteopaenia may provide an opportunity for early intervention as it raises the suspicion of Fanconi's syndrome. Previous case reports suggest there is a subpopulation of individuals who are at risk of developing this condition. These individuals share similar characteristics, including being non-ambulatory, developmentally delayed and/or tube fed. Withdrawing sodium valproate therapy is the ultimate treatment for valproate-induced Fanconi's syndrome and from previous case series, normalised renal function occurs in approximately 6 months. Often, supplement support is also required for deranged electrolyte balance.

Drug-induced acid-base disorders

The incidence of acid-base disorders (ABDs) is high, especially in hospitalized patients. ABDs are often indicators for severe systemic disorders. In everyday clinical practice, analysis of ABDs must be performed in a standardized manner. Highly sensitive diagnostic tools to distinguish the various ABDs include the anion gap and the serum osmolar gap. Drug-induced ABDs can be classified into five different categories in terms of their pathophysiology: (1) metabolic acidosis caused by acid overload, which may occur through accumulation of acids by endogenous (e.g., lactic acidosis by biguanides, propofol-related syndrome) or exogenous (e.g., glycol-dependant drugs, such as diazepam or salicylates) mechanisms or by decreased renal acid excretion (e.g., distal renal tubular acidosis by amphotericin B, nonsteroidal anti-inflammatory drugs, vitamin D); (2) base loss: proximal renal tubular acidosis by drugs (e.g., ifosfamide, aminoglycosides, carbonic anhydrase inhibitors, antiretrovirals, oxaliplatin or cisplatin) in the context of Fanconi syndrome; (3) alkalosis resulting from acid and/or chloride loss by renal (e.g., diuretics, penicillins, aminoglycosides) or extrarenal (e.g., laxative drugs) mechanisms; (4) exogenous bicarbonate loads: milk-alkali syndrome, overshoot alkalosis after bicarbonate therapy or citrate administration; and (5) respiratory acidosis or alkalosis resulting from drug-induced depression of the respiratory center or neuromuscular impairment (e.g., anesthetics, sedatives) or hyperventilation (e.g., salicylates, epinephrine, nicotine).

Fever of unknown origin as the initial manifestation of valproate-induced Fanconi syndrome

BACKGROUND

Valproate-induced Fanconi syndrome is a rare adverse effect of valproate. Severely disabled patients who require tube feeding are reported to be susceptible to valproate-induced Fanconi syndrome. Although most patients with valproate-induced Fanconi syndrome are asymptomatic and detected incidentally with findings such as hypophosphatemia, hypouricemia, increased urinary β2-microglobulin, and generalized hyperaminoaciduria, clinical symptoms such as bone fracture, fever, tachypnea, and edema have been reported.

PATIENT DESCRIPTION

This 15-year-old, severely disabled, tube-fed, male patient with cytochrome oxidase deficiency had taken valproate for 3 years when he developed fever for 3 weeks. Hypophosphatemia, hypouricemia, hypokalemia, increased urinary β2-microglobulin, and generalized hyperaminoaciduria, as well as hypocarnitinemia, were found, indicating that he had Fanconi syndrome. Valproate was the most likely cause of Fanconi syndrome in this patient. After discontinuation of valproate, the fever resolved immediately, and the laboratory findings normalized.

CONCLUSION

Valproate-induced Fanconi syndrome should be considered when individuals taking valproate develop fever of unknown origin.

The effects of sodium valproate on the renal function of children with epilepsy

Sodium valproate is one of the most commonly used drugs to treat epilepsy. However, there is growing evidence that valproate can cause renal tubular injury in children, and there are increasing reports of valproate-induced Fanconi's syndrome where the renal tubules lose their ability to reabsorb electrolytes, urea, glucose and protein. In this review article we attempt to bring together all of the studies conducted to date on the effects of valproate on renal function in epileptic children. The research is generally considered in two themes; the first comprises studies which indicate subclinical tubular injury measured by renal enzymes such as N-acetyl-β-D-glucosaminidase (NAG), and the second comprises clinical reports where Fanconi's syndrome has occurred. This article goes on to analyse the current data and draws on recurring patterns to suggest that a specific subpopulation of severely disabled epileptic children may benefit hugely from the close monitoring of enzymes which are indicative of renal tubular injury, particularly NAG or in the very least periodical urinalysis.

Carboplatin-induced Fanconi-like syndrome in rats: amelioration by pentoxifylline

INTRODUCTION

Carboplatin is a congener of cisplatin used in the treatment of ovarian, head and neck and small-cell lung cancer. However, the clinical efficacy of carboplatin is marred by the development of ROS-dependent nephrotoxicity. The pathophysiological damage inflicted upon the kidney by carboplatin closely resembles to that of Fanconi syndrome.

AIMS AND OBJECTIVES

The present study aimed at inducing Fanconi-like syndrome in rats by administration of carboplatin. Objectives of the study involved evaluation of biochemical parameters coherent to Fanconi-like syndrome. Further, an attempt was made to evaluate the potential therapeutic effect of pentoxifylline in this condition.

RESULTS

The results of the study demonstrated that the urinary excretion profile of carboplatin treated rats closely resembled to that of patients suffering from Fanconi-like condition. Pentoxifylline was able to ameliorate this nephrotoxic condition as suggested by the change in levels of membrane bound ATPases, MDA and GSH. The urinary levels of tyrosine and cysteine correlate well with that of Fanconi-like condition in animals and humans.

CONCLUSION

In lieu of these observations, our study suggested that carboplatin-induced renovascular damage resembles to Fanconi-like condition which can be mitigated by pentoxifylline.

Proximal renal tubular acidosis: a not so rare disorder of multiple etiologies

Proximal renal tubular acidosis (RTA) (Type II RTA) is characterized by a defect in the ability to reabsorb HCO₃ in the proximal tubule. This is usually manifested as bicarbonate wastage in the urine reflecting that the defect in proximal tubular transport is severe enough that the capacity for bicarbonate reabsorption in the thick ascending limb of Henle's loop and more distal nephron segments is overwhelmed. More subtle defects in proximal bicarbonate transport likely go clinically unrecognized owing to compensatory reabsorption of bicarbonate distally. Inherited proximal RTA is more commonly autosomal recessive and has been associated with mutations in the basolateral sodium-bicarbonate cotransporter (NBCe1). Mutations in this transporter lead to reduced activity and/or trafficking, thus disrupting the normal bicarbonate reabsorption process of the proximal tubules. As an isolated defect for bicarbonate transport, proximal RTA is rare and is more often associated with the Fanconi syndrome characterized by urinary wastage of solutes like phosphate, uric acid, glucose, amino acids, low-molecular-weight proteins as well as bicarbonate. A vast array of rare tubular disorders may cause proximal RTA but most commonly it is induced by drugs. With the exception of carbonic anhydrase inhibitors which cause isolated proximal RTA, drug-induced proximal RTA is associated with Fanconi syndrome. Drugs that have been recently recognized to cause severe proximal RTA with Fanconi syndrome include ifosfamide, valproic acid and various antiretrovirals such as Tenofovir particularly when given to human immunodeficiency virus patients receiving concomitantly protease inhibitors such as ritonavir or reverse transcriptase inhibitors such as didanosine.

Anticonvulsant-induced rickets and nephrocalcinosis

Reported here is the case of a severely disabled young girl who developed Fanconi syndrome secondary to long-term valproic acid administration, ultimately leading to hypophosphatemic rickets. Although nephrocalcinosis is not a common feature in patients with proximal tubulopathy, the patient presented also with this condition, and the concomitant use of another anticonvulsant might have potentiated this condition. The purpose of this report is to increase awareness among healthcare providers of such rare but significant complications associated with anticonvulsants.

Valproate-induced Fanconi syndrome in a 27-year-old woman

Valproate-induced Fanconi Syndrome (VFS) is a rare complication of this therapy that has been previously described only in children with epilepsy. We report the first known case of an adult with VFS. Metabolic derangements lead patients to present with fatigue, confusion, weakness, and even bone fractures. Identification and discontinuation of the offending agent is the treatment of choice and helps confirm the diagnosis. This case highlights the importance of surveillance for metabolic derangements among patients on long term therapy with this commonly prescribed medication.

Effects of Sodium Valproate on Renal Functions in Rats

In recent years, it has been reported that sodium valproate occasionally can cause renal tubular impairment. This study was designed to demonstrate the renal tubular and glomerular functions in rats given sodium valproate as monotherapy, as well as to determine any reversibility of dysfunctions. Female rats were randomly allocated to three groups: group 1 received sodium valproate 500 mg/kg/d intraperitoneal for six weeks; after the same injection period, group 2 was housed for another six weeks, after which laboratory investigations were completed; and group 3 served as a control group made up of 20 healthy rats living in same condition without any treatment. Serum ALT, total protein, uric acid, ALP, phosphorus, sodium levels, and urine Ca/cr ratio were significantly different between groups 1 and 3 (p < 0.025), but this difference was not seen between groups 2 and 3. On the other hand, other parameters such as TRP, Ccr, NAG, and MDA were not significantly different among the three groups ( p > 0.025) These results suggest that SV does not have a significant dose- or time-related side effect on renal functions. Minor biochemical dysfunctions related to long-term sodium valproate therapy is reversible, and the minimal renal fibrosis that showed histopathologically is not clinically important. The renal tissues of rats are known to show similar metabolic and histological patterns with human renal tissues. No renal dysfunction was expected in humans because there were no clinically statistically significant renal side effects in this study.

Bone consequences of epilepsy and antiepileptic medications

Childhood and adolescence are critical periods of skeletal mineralization. Peak bone mineral density achieved by the end of adolescence determines the risk for later pathological fractures and osteoporosis. Chronic disease and medication often adversely affect bone health. Epilepsy is one of the most common neurological conditions occurring in persons under the age of 21. Epilepsy may affect bone in a number of ways. Restrictions of physical activity imposed by seizures, cerebral palsy or other coexisting comorbidities adversely affect bone health. It has been observed that treatment with phenytoin and phenobarbital can be associated with rickets. More recently, established agents such as carbamazepine and valproate have been shown to be associated with decreased bone mineral density. The literature related to bone health in pediatric epilepsy is reviewed.

Evaluation of renal tubular function in children taking anti-epileptic treatment

AIM

To assess the effects of anti-epileptic drugs on renal tubular function.

METHODS

Urinary N-acetyl-beta-D-glucosaminidase activity was measured in 114 epileptic children (mean age 5.6 +/- 1.1 years) who were undergoing monotherapy with valproate (n = 46), carbamazepine (n = 34), lamotrigine (n = 13) and combined therapy with valproate+carbamazepine (n = 21).

RESULTS

The urinary N-acetyl-beta-D-glucosaminidase index of valproate (P < 0.01), carbamazepine (P < 0.05) and polytherapy group (P < 0.01) were significantly elevated when compared with that of the control group. No significant difference in N-acetyl-beta-D-glucosaminidase levels was found between the lamotrigine group and the control subjects. We found that the distribution of the N-acetyl-beta-D-glucosaminidase values of patients depended significantly on the length of therapy (P < 0.01). The level of urinary excretion of N-acetyl-beta-D-glucosaminidase was significantly higher in the patients who were taking long-term treatment (>10 years) with valproate, carbamazepine and combined therapy than those taking therapy shorter than 10 years (P < 0.01). The mean serum concentrations of valproate and carbamazepine were 68.7 +/- 17.44 microg/mL and 5.41 +/- 1.23 microg/mL, respectively. There was a significant correlation between the serum concentration of valproate and urinary N-acetyl-beta-D-glucosaminidase levels (r = 0.44, P < 0.01). There was also a significant correlation between the serum concentration of carbamazepine and N-acetyl-beta-D-glucosaminidase excretion (r = 0.52, P < 0.01).

CONCLUSION

The present study demonstrated that in patients treated with valproate and carbamazepine, an impairment of tubular function can be present, whereas lamotrigine does not cause any significant change.

Detection of maleate-induced Fanconi syndrome by decreasing accumulation of 125I-3-iodo-alpha-methyl-L-tyrosine in the proximal tubule segment-1 region of renal cortex in mice: a trial of separate evaluation of reabsorption

OBJECTIVE

Fanconi syndrome is a renal dysfunction characterized by various combinations of renal tubular transport dysfunction involving amino acids, glucose, protein and other substances. Most reabsorption of amino acids occurs in proximal renal tubule segment 1 (S1). The present study evaluated the possibility of early detection of drug-induced Fanconi syndrome, based on decreased renal accumulation of 125I-3-iodo-alpha-methyl-L-tyrosine (125I-IMT), an amino acid transport marker, in the S1 region of renal cortex. The present experimental model used maleate (MAL)-induced Fanconi syndrome in mice. Results were compared between 125I-IMT and 3 other clinical renal radiopharmaceuticals: 99mTc-2,3-dimercaptosuccinic acid (99mTc-DMSA); 99mTc-mercaptoacetylglycylglycylglycine (99mTc-MAG3); and 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA).

METHODS

Male ddY mice (age, 6 weeks; body weight, 25 g) were used to create a Fanconi model of renal dysfunction. A single dose of maleate disodium salt was administered by intraperitoneal injection (6 mmol/kg). Hematoxylin and eosin (HE) staining of the renal cortex, renal autoradiography and measurement of renal radioactivity of labeled compounds were performed at 30, 60, 90 and 120 min after MAL injection. At 5 min after injection of labeled compounds (18.5 kBq for accumulation experiment, 670 kBq for autoradiography), animals were sacrificed by ether overdose and kidneys were removed. For the accumulation experiment, radioactivity was measured using a well-type scintillation counter. For autoradiography, 20-microm sections of frozen kidney were used with Bio-Imaging Analyzer.

RESULTS

At 30 min after MAL injection, HE staining showed pyknosis in some proximal tubule cells. At that time, accumulations of 125I-IMT and 99mTc-DMSA in the S1 region were approximately 67% and 55% of control levels (p < 0.005). MAL increased accumulation of 99mTc-DTPA in the S1 region, but had no effect on accumulation of 99mTc-MAG3 in the S 1 region.

CONCLUSIONS

Decreased accumulation of 123I-IMT in the S1 region appears to represent a useful marker for detection of MAL-induced Fanconi syndrome. In future, we plan to assess the efficacy of using 125I-IMT to monitor renal dysfunction induced by nephrotoxic clinical drugs.

Secondary renal Fanconi syndrome caused by valproate therapy

Although renal Fanconi syndrome resulting from valproate (VPA) has occasionally been reported, the detailed clinical characteristics of this disease remain unclear. To clarify the clinical features of patients with VPA-induced Fanconi syndrome, we analyzed the clinical and laboratory data of seven affected patients. All patients were children, were severely disabled and required tube feeding. Five patients required treatment with multiple anticonvulsant agents. Hypophosphatemia and hypouricemia were found in all patients. Mild proteinuria, increased excretion of urinary beta2-microglobulin (beta2MG) and generalized hyperaminoaciduria were present in all patients. The renal biopsy of one patient exhibited tubulointerstitial nephritis without any structural abnormalities of the mitochondria in proximal renal tubular cells. All patients recovered from the Fanconi syndrome after the cessation of VPA therapy without any long-term renal sequellae. These results indicate that young age and being severely disabled with tube feeding and anticonvulsant polytherapy are contributory factors to the development of VPA-induced Fanconi syndrome. Serum phosphate and uric acid concentrations and urinary beta2MG levels in addition to serum electrolytes and urinalysis should be examined regularly in patients receiving VPA therapy, especially in those with the contributory factors outlined above. Patients with Fanconi syndrome caused by VPA have a favorable renal outcome.

Bone mineral metabolism changes in epileptic children receiving valproic acid

OBJECTIVE

The aim of this study was to evaluate bone mineral density (BMD) in epileptic children receiving valproic acid (VPA) and to determine differences between osteopenic and non-osteopenic children.

METHODS

Thirty-three epileptic children, receiving VPA for at least 6 months, were compared with 33 healthy children for BMD. BMD was measured by dual-energy X-ray absorptiometry at lumbar vertebrae, femoral neck and greater trochanter. Serum calcium, phosphorus, alkaline phosphates, osteocalcin and VPA levels were also determined.

RESULTS

Patient's osteocalcin levels were significantly higher (P = 0.02) and femur and trochanter BMD values were significantly lower (P = 0.04 and P = 0.03, respectively). Duration of VPA therapy was significantly longer and doses of VPA were significantly higher in seven osteopenic patients compared with 26 non-osteopenic patients. Osteopenic patients (4.6 +/- 2.4 years) were younger than non-osteopenic patients (7.8 +/- 3.2 years) (P = 0.01).

CONCLUSION

Long-term and high dose VPA therapy may cause osteopenia, primarily in younger epileptic children. These patients should be followed closely by BMD measurements.

Fanconi Syndrome Caused by Antiepileptic Therapy with Valproic Acid

PURPOSE

Valproic acid (VPA) is commonly used as an antiepileptic drug (AED). Regular screening for renal side effects is uncommon. Fanconi syndrome, a generalized dysfunction of renal proximal tubular cells, occurs with some inborn errors of metabolism. In addition, it can be acquired by exposure to several toxic substances. We report a case of Fanconi syndrome after long-term therapy with VPA.

METHODS

An 8-year-old severely disabled and developmentally retarded boy with epilepsy was treated with VPA over a period of 7 years. He was hospitalized after a status epilepticus with laboratory findings suggesting a Fanconi syndrome. A PubMed-based worldwide review of the literature revealed that Fanconi syndrome is a rare side effect in children during long-term VPA treatment. We analyzed all 10 previously published cases by comparing age, underlying diseases, medication, and outcome.

RESULTS

Examination revealed metabolic acidosis suggestive of renal tubular malfunction. Based on typical clinical and laboratory findings, an acquired Fanconi syndrome was diagnosed. This was treated with large doses of sodium bicarbonate. After discontinuation of VPA, renal function completely normalized within 2 months.

CONCLUSIONS

Fanconi syndrome appears to be a rare but severe consequence of long-term VPA therapy. Therefore patients treated with VPA should be checked regularly for the possible development of VPA-induced Fanconi syndrome.

Treatment of anticonvulsant drug-induced bone disease

Although the pathophysiology of bone disease in patients treated with anticonvulsant drugs may vary, most affected patients have increased bone remodeling rather than decreased mineralization. Milder cases may show high bone turnover without significant loss of cortical or trabecular bone. Cases of intermediate severity may exhibit the characteristic features of a high-turnover osteopenia/osteoporosis, but some patients with severe bone disease may manifest the features of an osteomalacic disorder. Prophylactic vitamin D supplementation at doses up to 2000 IU/day can be recommended for all patients on initiation of anticonvulsant therapy. A calcium intake of 600-1000 mg/day should also be ensured. If an osteopenic/osteoporotic disorder exists, treatment with 2000-4000 IU/day vitamin D is appropriate. Vitamin D doses of 5000-15,000 IU/day may be needed to treat osteomalacia. Conventional treatment with bisphosphonates may be needed when the response to vitamin D is inadequate. However, routine use of bisphosphonates in patients receiving long-term anticonvulsant therapy cannot at present be recommended.

Hypouricemia in severely disabled children: influence of valproic acid and bed-ridden state

Although hypouricemia does not directly elicit clinical symptoms, it is a sensitive indicator for detecting renal tubular involvement. To determine the influence of valproic acid (VPA) and a non-ambulatory state on the serum uric acid level in epileptic children, we performed a cross-sectional study of laboratory data including serum and urinary uric acid levels and renal tubular function levels in epileptic children. We studied 93 patients in our outpatient clinic. They were divided into four groups according to two factors; VPA administration and the ambulatory state: non-ambulatory patients taking VPA (24 cases), non-ambulatory patients not taking VPA (18 cases), ambulatory patients taking VPA (29 cases), and ambulatory patients not taking VPA (22 cases). The laboratory data including uric acid levels and renal tubular function in each group were analyzed statistically using analysis of variance. Both VPA (P<0.05) and a non-ambulatory state (P<0.01) significantly decreased the serum uric acid levels with its increased urinary excretion of uric acid. However, in ambulatory patients, the uric acid level was not decreased. Serum uric acid levels was significantly decreased in non-ambulatory, severely disabled children treated with VPA. It should be borne in mind that VPA-induced renal tubular dysfunction may be present in severely disabled children. However, further investigation is necessary to determine the factor in severely disabled children that causes hypouricemia

Renal injury from valproic acid: case report and literature review

A child with developmental delay and epilepsy developed glucosuria approximately 16 months after starting valproic acid therapy. Laboratory evaluation revealed global defects in proximal tubule function consistent with the De Toni-Debré-Fanconi syndrome. Discontinuation of valproate led to complete recovery 5 months later. Review of previously reported cases indicates that this complication is unique to children and reversible when the medication is discontinued.

Tubulo-interstitial nephritis caused by sodium valproate

A severely handicapped 14-year-old Japanese girl had epilepsy and was treated with sodium valproate (SV) from the age of 7 years. Although the epileptic seizures were well controlled, she sometimes had a fever and hypokalemia from the age of 13 years. Laboratory examinations revealed metabolic acidosis, hypouricemia, hypophosphatemia, glycosuria, proteinuria and aminoaciduria, thus suggesting Fanconi syndrome. Gallium scanning showed marked renal uptake. A renal biopsy revealed interstitial nephritis without immuno-deposition. SV was replaced since it was considered to be the most probable cause of the renal involvement. Thereafter, she showed marked improvement of the clinical symptoms and the laboratory data gradually, and she never had a fever. Although SV is an effective anti-epileptic drug, we have to pay attention to adverse renal effects such as Fanconi syndrome and interstitial nephritis.

Osteoporosis in children and adolescent girls: case report of idiopathic juvenile osteoporosis and review of the literature

The diagnosis and treatment of osteoporosis is an important aspect of gynecologic training and practice. Idiopathic juvenile osteoporosis (IJO) is a rare disease of children and adolescents that resolves after the onset of puberty. A case report is presented and current methods of diagnosis and treatment of IJO are discussed as well as the differential diagnosis. A MEDLINE search was performed of the following terms: idiopathic juvenile osteoporosis, pediatric osteoporosis, adolescent osteoporosis, bisphosphonates pediatric adolescent, and pregnancy osteoporosis, and references from bibliographies of selected papers were used as well. All papers in English, French, and German are considered in this review. There were 114 papers selected as relevant to the topic. Data relevant to the diagnosis, pathogenesis, methods of imaging, laboratory evaluation, differential diagnosis, and treatment of IJO are presented. IJO is a diagnosis of exclusion in the pediatric and adolescent patient with osteoporosis. Although bone density gradually improves after the onset of puberty, treatment of currently affected children and adolescents involves activity restriction, calcium, vitamin D, and bisphosphonate therapy. Future reproductive concerns are discussed and areas requiring additional study are reviewed.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader will be able to describe the condition idiopathic juvenile osteoporosis, compare the clinical features of this condition to other similar conditions, outline the diagnostic workup of a child with this condition, and list the potential therapeutic options for a patient with idiopathic juvenile osteoporosis.

Valproate, but not lamotrigine, induces ovarian morphological changes in Wistar rats

Valproate (VPA) medication is associated with development of polycystic ovaries, menstrual disorders and hormonal changes in women with epilepsy. We sought to determine if changes in the ovaries also occurred in an animal model without epilepsy, and whether this effect could be related to a carcinogenic effect expressed by overexpression of p53. A potentially alternative antiepileptic drug, lamotrigine (LTG), was evaluated simultaneously. To this end, female Wistar rats were fed perorally with VPA 400 mg/kg/day (n = 15), VPA 600 mg/kg/day (n = 20), LTG 10 mg/kg/day (n = 15) or control solution (n = 15) for 90-95 days. There was a significant, dose-dependent increase in the number of follicular cysts, reduction in the number of corpora lutea and reduction of ovarian weight in the VPA group. No ovarian pathology was observed in the LTG group. In neither of the groups were morphological changes seen in other organs, nor was there any overexpression of the tumor suppressor gene p53 found. An alternative antiepileptic drug, LTG, showed no ovarian pathology, and there were no light microscopic changes in other organs, or evidence of pathologic p53 overexpression in the LTG-treated animals.

Induction of an experimental Fanconi syndrome in mice: its effect on the glomerular filtration function studied by 99mTc-DTPA

An experimental mice model of maleate (MAL)-induced Fanconi syndrome has been used to test 99mTc-DTPA ability to detect hampered glomerular filtration rate (GFR) early in drug-induced Fanconi syndrome. In fact, declining GFR has been reported both in idiopathic and acquired Fanconi syndrome. The above MAL model shows urine biochemistry changes similar to those reported in patients suffering from Fanconi syndrome. Moreover, biodistribution study and whole-body autoradiographies performed after IV injection of 99mTc-DTPA in MAL and control mice show significantly delayed pharmacokinetics of the above radiopharmaceutical in a MAL dose-dependent effect. After administration of a MAL dose of 6 mM/kg BW, the 5-min biodistribution of 99mTc-DTPA, a radiopharmaceutical freely excreted by glomerular filtration, is significantly changed in all organs. In blood of MAL mice, 27.62 +/- 2.86% of the injected dose is still circulating compared to 13.67 +/- 1.22% of the injected dose in control mice, and only 1.37 +/- 0.31% of the injected dose has been excreted in urine of MAL mice compared to 24.66 +/- 4.12% of the injected dose in urine of control mice. The obtained results suggest that 99mTc-DTPA may be efficient both in the early detection of abnormal GFR in acquired Fanconi syndrome after application of a nephrotoxic treatment, and in the follow-up of patients in recovery phase after discontinuation of the therapy.

Effect of carbamazepine and valproate on bone mineral density

OBJECTIVE

To examine the effect of carbamazepine and valproate monotherapy on bone mineral density in children.

METHODS

Axial (second, third, and fourth lumbar vertebrae) and appendicular (distal third of radius) bone mineral density was measured by dual-energy x-ray absorptiometry in 27 healthy children and 26 children with uncomplicated idiopathic epilepsy treated with either carbamazepine (n = 13) or valproate (n = 13) for more than 18 months. Control subjects and patients were similar with respect to age, race (all white), and geographic area, and had no dietary restrictions, neurologic impairment, or physical handicaps.

RESULTS

Subjects were seizure-free for more than 6 months on a regimen of carbamazepine or valproate therapy, and had mean serum trough levels of 6.88 +/- 2 micrograms/ml and 72.04 +/- 45.6 micrograms/ml, respectively. Dietary calcium intake was similar in control and treated groups. After correction for gender and age, children treated with valproate had a 14% (p = 0.003) and 10% (p = 0.005) reduction in bone mineral density at the axial and appendicular sites, respectively. The reduction in bone mineral density increased with the duration of valproate therapy. Carbamazepine did not significantly reduce bone mineral density.

CONCLUSION

Valproate montherapy, but not carbamazepine therapy, significantly reduces axial and appendicular bone mineral density in children with idiopathic epilepsy and may increase their risk of osteoporotic fractures.