Use of Antiepileptic Drugs in Patients with Kidney Disease

Serum perampanel levels in patients with seizures are not affected by hemodialysis

Perampanel belongs to a novel class of antiseizure medications (ASMs). Studies examining the effect of hemodialysis on perampanel serum levels in clinical settings are lacking. We aimed to evaluate the changes in serum perampanel levels during hemodialysis. We studied patients with seizures who received oral perampanel between April 2020 and March 2023 and whose serum concentration of perampanel was measured before and after hemodialysis. We analyzed the serum concentrations of levetiracetam and lacosamide for comparison. Fourteen patients, with a mean age of 76.1 ± 7.88 years, were included. The dose of perampanel was 2.14 ± 1.27 mg. The hemodialysis clearance rate of perampanel, levetiracetam, and lacosamide was 0 ± 13%, 69 ± 11%, and 59.6 ± 8.2%, respectively. The post-dialysis CD ratio decreased significantly with levetiracetam but not with perampanel. Adverse but acceptable effects of perampanel were observed in two patients. The serum concentrations of several ASMs have been shown to be reduced during hemodialysis. Our study revealed that the serum perampanel concentration does not decrease during hemodialysis. Owing to the low rate of adverse effects and the stability of perampanel serum concentration during hemodialysis, perampanel could be a favorable choice as an ASM for patients with seizures undergoing hemodialysis. PLAIN LANGUAGE SUMMARY: Our study looked at how hemodialysis affects the serum levels of perampanel, a new type of medication for seizures. In 14 patients who started treatment between April 2020 and March 2023, perampanel serum levels did not decrease during hemodialysis, unlike other seizure medications. This shows that perampanel can be a good option for patients with seizures who need hemodialysis, with fewer side effects compared to other medications.

Decision support for comorbid conditions via execution-time integration of clinical guidelines using transaction-based semantics and temporal planning

In case of comorbidity, i.e., multiple medical conditions, Clinical Decision Support Systems (CDSS) should issue recommendations based on all relevant disease-related Clinical Practice Guidelines (CPG). However, treatments from multiple comorbid CPG often interact adversely (e.g., drug-drug interactions) or introduce operational inefficiencies (e.g., redundant scans). A common solution is the a-priori integration of computerized CPG, which involves integration decisions such as discarding, replacing or delaying clinical tasks (e.g., treatments) to avoid adverse interactions or inefficiencies. We argue this insufficiently deals with execution-time events: as the patient's health profile evolves, acute conditions occur, and real-time delays take place, new CPG integration decisions will often be needed, and prior ones may need to be reverted or undone. Any realistic CPG integration effort needs to further consider temporal aspects of clinical tasks-these are not only restricted by temporal constraints from CPGs (e.g., sequential relations, task durations) but also by CPG integration efforts (e.g., avoid treatment overlap). This poses a complex execution-time challenge and makes it difficult to determine an up-to-date, optimal comorbid care plan. We present a solution for dynamic integration of CPG in response to evolving health profiles and execution-time events. CPG integration policies are formulated by clinical experts for coping with comorbidity at execution-time, with clearly defined integration semantics that build on Description and Transaction Logics. A dynamic planning approach reconciles temporal constraints of CPG tasks at execution-time based on their importance, and continuously updates an optimal task schedule.

Kidney Disease and Epilepsy

Chronic kidney disease and seizures often co-exist. When seizures are provoked in patients with kidney disease, their treatment poses a particular challenge. Seizures may be provoked in the context of uremia, and toxic substances associated with uremic encephalopathy. In that case, the mainstay of therapy is to treat the uremia before consideration for anticonvulsant therapy. Treatment of seizures in the setting of chronic kidney disease requires special attention to selection of anticonvulsant medications and knowledge of the altered pharmacokinetics of these medications, which may require special titration schedule in that setting. The purpose of this review is to summarize the current knowledge about inter-relation of seizures and kidney disease. The review will also help practitioners who treat patients with renal failure and coexisting seizures in choosing the best treatment options.

Pharmacotherapeutic Management of Neuropathic Pain in End-Stage Renal Disease

Background

Chronic noncancer pain is pervasive throughout the general patient population, transcending all chronic disease states. Patients with end-stage renal disease (ESRD) present a complicated population for which medication management requires careful consideration of the pathogenesis of ESRD and intimate knowledge of pharmacology. The origin of pain must also guide treatment options. As such, the presentation of neuropathic pain in ESRD can present a challenging case. The authors aim to provide a review of available classes of medications and considerations for the treatment of neuropathic pain in ESRD.

Summary

In this narrative review, the authors discuss important strategies and considerations for the treatment of neuropathic pain in ESRD, including the pathogenesis of neuropathic pain, physiological changes for consideration in ESRD patients, and disease-specific consideration for medication selection. Pharmacotherapeutic classes discussed include: anticonvulsants, antiarrhythmics, antidepressants, topicals, and opioids.

Key Message

Pain management in ESRD patients requires careful assessment of drug-specific properties, accumulation, metabolism (presence of active/toxic metabolites), extraction by dialysis, and presence of drug - drug interactions. In the absence of pharmacokinetic data in ESRD patients, therapeutic window and potential risks should be factored in the decision making along with continued monitoring throughout therapy.

Neurologic conditions and disorders of uremic syndrome of chronic kidney disease: presentations, causes, and treatment strategies

Introduction: Uremic syndrome of chronic kidney disease (CKD) is a term used to describe clinical, metabolic, and hormonal abnormalities associated with progressive kidney failure. It is a rapidly growing public health problem worldwide. Nervous system complications occur in every patient with uremic syndrome of CKD. Areas covered: This review summarized central and peripheral nervous system complications of uremic syndrome of CKD and their pathogenic mechanisms. They include cognitive deterioration, encephalopathy, seizures, asterixis, myoclonus, restless leg syndrome, central pontine myelinolysis, stroke, extrapyramidal movement disorders, neuropathies, and myopathy. Their pathogenic mechanisms are complex and multiple. They include (1) accumulation of uremic toxins resulting in neurotoxicity, blood-brain barrier injury, neuroinflammation, oxidative stress, apoptosis, brain neurotransmitters imbalance, ischemic/microvascular changes, and brain metabolism dysfunction (e.g. dopamine deficiency), (2) metabolic derangement (as acidosis, hypocalcemia, hyperphosphatemia, hypomagnesemia, and hyperkalemia); (3) secondary hyperparathyroidism, (4) erythropoietin and iron deficiency anemia, (5) thiamin, vitamin D, and other nutritional deficiencies, (6) hyperhomocysteinemia, and (7) coagulation problems. Expert commentary: Nervous system complications of uremia contribute to the patients' morbidity and mortality. Optimizing renal replacement therapy, correction of associated metabolic and medical conditions, and improved understanding of possible pathogenic mechanisms of these complications is a major target for their prevention and treatment.

Renal Disease and Neurology

PURPOSE OF REVIEW

Neurologic dysfunction is prevalent in patients with acute and chronic renal disease and may affect the central nervous system, peripheral nervous system, or both. Neurologic manifestations may result directly from the uremic state or as a consequence of renal replacement therapy. Early recognition of neurologic dysfunction may provide opportunities for intervention and reduced morbidity.

RECENT FINDINGS

Advances in the understanding of neurologic complications of renal disease and its treatments have led to more widespread recognition and earlier identification of encephalopathy syndromes such as cefepime neurotoxicity and posterior reversible encephalopathy syndrome (PRES), dramatic reductions in the incidence of dialysis disequilibrium syndrome and dialysis dementia, and improved survival in disorders such as von Hippel-Lindau disease and thrombotic thrombocytopenic purpura.

SUMMARY

This article summarizes the conditions that affect both the renal and the nervous systems, the effects of renal failure on the nervous system, and the neurologic complications of dialysis.

Epilepsy treatment in adults and adolescents: Expert opinion, 2016

INTRODUCTION

There are over twenty anti-seizure medications and anti-seizure devices available commercially in the United States. The multitude of treatment options for seizures can present a challenge to clinicians, especially those who are not subspecialists in the epilepsy field. Many clinical questions are not adequately answered in double-blind randomized controlled studies. In the presence of a knowledge gap, many clinicians consult a respected colleague with acknowledged expertise in the field. Our survey was designed to provide expert opinions on the treatment of epilepsy in adults and adolescents.

METHOD

We surveyed a group of 42 physicians across the United States who are considered experts based on publication record in the field of epilepsy, or a leadership role in a National Association of Epilepsy Centers comprehensive epilepsy program. The survey consisted of 43 multiple-part patient scenario questions and was administered online using Redcap software. The experts provided their opinion on 1126 treatment options based on a modified Rand 9-point scale. The patient scenarios focused on genetically-mediated generalized epilepsy and focal epilepsy. The scenarios first focused on overall treatment strategy and then on specific pharmacotherapies. Other questions focused on treatment of specific patient populations (pregnancy, the elderly, patients with brain tumors, and post organ transplant patients), epilepsy patients with comorbidities (renal and hepatic disease, depression), and how to combine medications after failure of monotherapy. Statistical analysis of data used the expert consensus method.

RESULTS

Valproate was considered a drug of choice in all genetically-mediated generalized epilepsies, except in the population of women of child-bearing age. Ethosuximide was a drug of choice in patient with absence seizures, and levetiracetam was a drug of choice in patients with genetic generalized tonic-clonic seizures and myoclonic seizures. Lamotrigine, levetiracetam and oxcarbazepine were considered drugs of choice for initial treatment of focal seizures. Lamotrigine and levetiracetam were the drugs of choice for women of child-bearing age with either genetic generalized epilepsy or focal epilepsy. Lamotrigine and levetiracetam were the drugs of choice in the elderly population. Lamotrigine was preferred in patients with co-morbid depression. Levetiracetam was the drug of choice in treating patients with hepatic failure, or who have undergone organ transplantation. Compared to the 2005 and 2001 surveys, there was increased preference for the use of levetiracetam and lamotrigine, and decreased preference for the use of phenytoin, gabapentin, phenobarbital and carbamazepine.

DISCUSSION

The study presented here provides a "snapshot" of the clinical practices of experts in the treatment of epilepsy. The experts were very often in agreement, and reached consensus in 81% of the possible responses. However, expert opinion does not replace the medical literature; instead, it acts to supplement existing information. Using the study results is similar to requesting an expert consultation. Our findings suggest options that the clinician should consider to achieve best practice.

Neurological consults on the renal unit

Neurological symptoms commonly occur in chronic kidney disease and may result from its treatments and complications. Impaired renal function also influences treatments for other neurological conditions, requiring various cautions, dose adjustments and timing considerations, particularly in the context of renal replacement therapy. In this review, we present six illustrative clinical vignettes to highlight these challenges.

Topiramate for Treatment in Patients With Migraine and Epilepsy

BACKGROUND

Antiepileptic drugs (AED) are often considered first line for monotherapy in treatment of patients with migraines, and also those with comorbid migraine and epilepsy. Topiramate, a newer generation AED, has broad mechanism of action and evidence of benefit in patients with either episodic or chronic migraine along with epilepsy, both generalized and focal.

METHODS

Our goal is to review the relevant mechanisms of action along with any supportive evidence published to date on the use of topiramate (TPM) in patients with both migraine headache and epilepsy.

CONCLUSIONS

There has been very little published to date on the use of TPM in patients diagnosed with both disorders. Despite this, TPM has been adopted as first line therapy in this patient population. Future studies investigating the effectiveness of this treatment strategy are warranted in order to determine the most effective use of this medication in patients diagnosed with migraine headaches and epilepsy.

Use of Antiepileptic Drugs in Patients with Chronic Kidney Disease and End Stage Renal Disease

Epilepsy is a disorder with an approximate worldwide prevalence of 1%. Due to complexities of metabolism, protein-binding, renal elimination, and other pharmacokinetic parameters, the dosing of antiepileptic drugs (AEDs) in patients with chronic kidney disease (CKD) or end stage renal disease (ESRD) deserves special attention. This is a review of the most commonly prescribed AEDs with special focus on their indication, pharmacokinetics, and unique considerations for use in patients with CKD and ESRD. A review of their renal toxicities is also included.

Trends in pediatric urolithiasis: patient characteristics, associated diagnoses, and financial burden

BACKGROUND

The goal of this study was to examine national trends in hospitalization, emergency department (ED) utilization, secondary diagnoses, and charges associated with pediatric urolithiasis.

METHODS

Data were evaluated from the Kids' Inpatient Database of the Healthcare Costs and Utilization Project (HCUP) database from 1997 to 2012 and the HCUP National ED Sample from 2006 to 2011.

RESULTS

Pediatric nephrolithiasis discharges increased by 18%, while ureterolithiasis discharges decreased by 17%. Hospital charges increased by 20% when accounting for inflation, despite an overall decrease in discharges by 2.5%. Female patients and those aged 15-17 years were more commonly affected. Pediatric ED visits increased by 9%. The most common secondary diagnoses during 2003-2009 were urinary tract infections (UTI) (13%), asthma (9%), epilepsy (4%), and paralysis (4%).

CONCLUSIONS

Decreased hospitalizations and increased ED visits indicate a shift to outpatient care. Inpatient health care charges associated with pediatric urolithiasis continue to rise. Comorbidities include UTI, asthma, epilepsy, attention deficit hyperactivity disorder (ADHD), and mood disorders. Because of the significant health care burden and the increased risk to children of developing long-term sequelae there is a strong need for increased research into the mechanism of this systemic inflammatory disease and improved therapeutic targets.

The Spanish Society of Neurology's official clinical practice guidelines for epilepsy. Special considerations in epilepsy: comorbidities, women of childbearing age, and elderly patients

INTRODUCTION

The characteristics of some population groups (patients with comorbidities, women of childbearing age, the elderly) may limit epilepsy management. Antiepileptic treatment in these patients may require adjustments.

DEVELOPMENT

We searched articles in Pubmed, clinical practice guidelines for epilepsy, and recommendations by the most relevant medical societies regarding epilepsy in special situations (patients with comorbidities, women of childbearing age, the elderly). Evidence and recommendations are classified according to the prognostic criteria of Oxford Centre of Evidence-Based Medicine (2001) and the European Federation of Neurological Societies (2004) for therapeutic interventions.

CONCLUSIONS

Epilepsy treatment in special cases of comorbidities must be selected properly to improve efficacy with the fewest side effects. Adjusting antiepileptic medication and/or hormone therapy is necessary for proper seizure management in catamenial epilepsy. Exposure to antiepileptic drugs (AED) during pregnancy increases the risk of birth defects and may affect fetal growth and/or cognitive development. Postpartum breastfeeding is recommended, with monitoring for adverse effects if sedative AEDs are used. Finally, the elderly are prone to epilepsy, and diagnostic and treatment characteristics in this group differ from those of other age groups. Although therapeutic limitations may be more frequent in older patients due to comorbidities, they usually respond better to lower doses of AEDs than do other age groups.

Treating epilepsy in the setting of medical comorbidities

OPINION STATEMENT

Treatment of epilepsy in patients with medical comorbidities can be challenging. Comorbidities can affect medical management and quality of life. In this review, we discuss treatment options in patients with epilepsy and medical comorbidities. In our opinion, the best way to manage patients with medical comorbidities and epilepsy is to accurately recognize and diagnose medical comorbidities, and to have adequate knowledge and familiarity with antiepileptic drug (AED) metabolism, dosing, side effects, and drug interactions. We believe the trend should move toward using the newer generation of AEDs given their generally reduced rate of adverse effects and interactions. The primary goal of therapy is seizure freedom without side effects.

Use of antiepileptic drugs in hepatic and renal disease

The use of antiepileptic drugs in patients with renal or hepatic disease is common in clinical practice. Since the liver and kidney are the main organs involved in the elimination of most drugs, their dysfunction can have important effects on the disposition of antiepileptic drugs. Renal or hepatic disease can prolong the elimination of the parent drug or an active metabolite leading to accumulation and clinical toxicity. It can also affect the protein binding, distribution, and metabolism of a drug. The protein binding of anionic acidic drugs, such as phenytoin and valproate, can be reduced significantly by renal failure, causing difficulties in the interpretation of total serum concentrations commonly used in clinical practice. Dialysis can further modify the pharmacokinetic parameters or result in significant removal of the antiepileptic drugs. Antiepileptic drugs that are eliminated unchanged by the kidneys or undergo minimal metabolism include gabapentin, pregabalin, vigabatrin, and topiramate when used as monotherapy. Drugs eliminated predominantly by biotransformation include phenytoin, valproate, carbamazepine, tiagabine, and rufinamide. Drugs eliminated by a combination of renal excretion and biotransformation include levetiracetam, lacosamide, zonisamide, primidone, phenobarbital, ezogabine/retigabine, oxcarbazepine, eslicarbazepine, ethosuximide, and felbamate. Drugs in the latter group can be used cautiously in patients with either renal or liver failure. Antiepileptic drugs that are at high risk of being extracted by hemodialysis include ethosuximide, gabapentin, lacosamide, levetiracetam, pregabalin and topiramate. The use of antiepileptic drugs in the presence of hepatic or renal disease is complex and requires great familiarity with the pharmacokinetics of these agents. Closer follow-up of the patients and more frequent monitoring of serum concentrations are required to optimize clinical outcomes.

Management of chronic pain in elderly, frail patients: finding a suitable, personalized method of control

The elderly population is projected to make up 20% of the total United States population by the year 2030. In addition, epidemiological data suggests increasing prevalence of chronic pain and frailty with advancing age. Pain, being a subjective symptom, is challenging to manage effectively. This is more so in elderly populations with age-specific physiological changes that affect drug action and metabolism. Elderly patients are also more likely to have multiple chronic health pathologies, declining function, and frailty. The barriers present for patients, providers, and health systems also negatively impact efficient and effective pain control. These factors result in disproportionate utilization of health resources by the older population group. The scientific literature is lagging behind in age-specific studies for the elderly population. As a result, there is a lack of age-specific standardized management guidelines for various health problems, including chronic pain. Increasing efforts are now being directed to studies on pain control in the elderly. However, pain management remains inconsistent and suboptimal. This article is an attempt to suggest an informed, comprehensive guide to achieve effective pain control in the presence of these limitations.

An update on neurocritical care for the patient with kidney disease

Patients with kidney disease have increased rates of neurologic illness such as intracerebral hemorrhage and ischemic stroke. The acute care of patients with critical neurologic illness and concomitant kidney disease requires unique management considerations including attention to hyponatremia, renal replacement modalities in the setting of high intracranial pressure, reversal of coagulopathy, and seizure management to achieve good neurologic outcomes.

Neurologic manifestations of acute and chronic renal disease

Acute and chronic renal disease is prevalent in hospitalized and ambulatory patient populations. Most patients with acute or chronic renal disease exhibit some degree of neurologic dysfunction affecting the CNS, peripheral nervous system, or both. Neurologic manifestations may be a direct consequence of the uremic state or a consequence of renal replacement therapy. Early recognition of common central and peripheral nervous system dysfunction as it relates to renal disease may provide opportunities for therapeutic intervention and improved outcomes. This review will summarize the most frequently encountered manifestations of acute and chronic renal disease, organized with respect to their occurrence as a direct consequence of advanced renal dysfunction or renal replacement therapy.

[Pharmacotherapy in patients suffering from chronic kidney disease]

The number of patients suffering from chronic kidney disease (CKD) is increasing worldwide and exceeds 15% of the entire population in industrialized countries. Half of the patients aged 70 + years suffer from CKD. The most prevalent underlying diseases leading to CKD are diabetes and hypertension. CKD per se increases the risk of cardiovascular events, cancer, and infections; hence, adequate and intensified pharmacotherapy is of utmost importance in this patient population. About 60% of all regularly used drugs are excreted by the kidney. For those, dose adjustment is of utter importance to avoid untoward effects and serious complications. The first important step for dose adjustment is the accurate estimation of renal function, i.e., glomerular filtration rate (GFR). Renal function cannot be assessed by serum creatinine alone as it only rises after a substantial (> 50%) loss of glomerular function and depends on many factors, e.g., age, gender, weight, and race. GFR can easily be estimated using formulas, e.g., the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula.

The use of newer antiepileptic drugs in patients with renal failure

Seizures and chronic kidney disease are both common and often coexist. Treating seizures in patients with renal failure, including those on dialysis, is a challenge that is frequently encountered, especially in the inpatient setting. For the newer antiepileptic drugs, there are limited data available, so an understanding of how each drug is affected by kidney disease and dialysis is critical in order to make rational choices qualitatively (which drug) and quantitatively (dosing). Generally, newer (second-generation) antiepileptic drugs are associated with fewer systemic side effects and drug-drug interactions, so they tend to be preferred in this population. The landscape of antiepileptic drugs is constantly evolving, with new compounds being released on a regular basis. Thus, several new agents have become available since the last review of this topic (in 2006) and these are the ones discussed here. Most require dosage adjustment according to the degree of renal failure, and most require extra doses after dialysis.

Effectiveness of hemodialysis in a case of severe valproate overdose

A case of severe sodium valproate overdose is presented in which medicinal management failed to reverse coma of the patient. High-flux hemodialysis was then used to eliminate sodium valproate. This case demonstrated the effectiveness of hemodialysis in not only decreasing valproate levels very rapidly but also as an effective anti-coma management.

Effectiveness of hemodialysis in a case of severe valproate overdose

A case of severe sodium valproate overdose is presented in which medicinal management failed to reverse coma of the patient. High-flux hemodialysis was then used to eliminate sodium valproate. This case demonstrated the effectiveness of hemodialysis in not only decreasing valproate levels very rapidly but also as an effective anti-coma management.

Antiepileptic treatment in patients with epilepsy and other comorbidities

BACKGROUND

A high number of patients with epilepsy have comorbidities. The type of comorbidity is an important factor in deciding on the most suitable treatment, including that for acute epileptic seizures and chronic antiepileptic treatment. Evidence-based criteria should guide the selection of the appropriate antiepileptic drugs given specific comorbidities.

METHODS

We performed a comprehensive search of the scientific literature on epilepsy treatment in patients with the following comorbidities: heart disease, lung disease, liver disease, kidney disease, porphyria, organ transplantation, thyroid disease, metabolic disorder, infection, mental disability, psychiatric disorder, cognitive impairment, stroke, and brain tumour.

RESULTS

Most of the studies were case series and retrospective analyses. No randomised controlled trials specifically designed for this type of clinical situation were identified. The level of scientific evidence to guide clinical decisions is therefore low.

CONCLUSIONS

In this review we make recommendations based on the best scientific evidence available for treating epilepsy in patients with other comorbidities, including the treatment of epileptic seizures in acute situations as well as chronic antiepileptic treatment. When no scientific evidence is available, our recommendations are based on pharmacokinetic criteria and tolerability of antiepileptic drugs, using accumulated experience and the consensus of the members of the Andalusian Epilepsy Society.

Neurological complications of chronic kidney disease

Chronic kidney disease (CKD) is a critical and rapidly growing global health problem. Neurological complications occur in almost all patients with severe CKD, potentially affecting all levels of the nervous system, from the CNS through to the PNS. Cognitive impairment, manifesting typically as a vascular dementia, develops in a considerable proportion of patients on dialysis, and improves with renal transplantation. Patients on dialysis are generally weaker, less active and have reduced exercise capacity compared with healthy individuals. Peripheral neuropathy manifests in almost all such patients, leading to weakness and disability. Better dialysis strategies and dietary modification could improve outcomes of transplantation if implemented before surgery. For patients with autonomic neuropathy, specific treatments, including sildenafil for impotence and midodrine for intradialytic hypotension, are effective and well tolerated. Exercise training programs and carnitine supplementation might be beneficial for neuromuscular complications, and restless legs syndrome in CKD responds to dopaminergic agonists and levodopa treatment. The present Review dissects the pathophysiology of neurological complications related to CKD and highlights the spectrum of therapies currently available.

Psychotropic drugs and renal failure: translating the evidence for clinical practice

INTRODUCTION

The kidney is a primary route of drug elimination; abnormal kidney function is predicted to alter the pharmacokinetics of agents metabolized and/or excreted predominantly through this route. The high prevalence of mental disorders associated with psychotropic drug use in individuals with deteriorating renal function suggests there is a need to investigate the effects of renal failure on psychotropic pharmacokinetics. The aim of this review is to provide a clinically accessible overview of the effect of chronic renal failure on the pharmacokinetics for each of the major classes of prescribed psychotropic agents.

METHODS

All English language articles published between 1977 and 2008 were searched through PubMed, using the following keywords: "renal," "kidney," "pharmacokinetics," "renal impairment," "renal insufficiency," and "renal failure." Each of these search words was cross-referenced with the non-proprietary name of each psychotropic agent. The manufacturer's product insert was also reviewed for some agents for updated dosing. Owing to the lack of adequately powered studies, an inclusive manner was used.

RESULTS

Chronic renal failure variably affects the pharmacokinetic parameters of psychotropic drugs. A review of each psychotropic drug is provided, with an emphasis on the individual pharmacokinetic parameters and recommended dosing.

CONCLUSIONS

The adjudication of safe and effective doses for any psychotropic agent needs to be individualized. Tactics including dosage adjustment, slow titration, and careful monitoring for serious adverse events should be incorporated into practice.

Phenytoin metabolite renal calculus: an index case

INTRODUCTION

Drugs and their metabolites are known factors in 1% to 2% of all kidney stones. Certain antiepileptic drugs are known to cause stone formation. Phenytoin is used as a first line antiepileptic therapy for many seizure disorders. We present what we believe to be the first report of a phenytoin metabolite urinary stone.

METHODS

A 79-year-old woman with a fever and seizure disorder was found to have a right pelvic kidney with hydronephrosis and multiple large calcifications. She had been taking the antiepileptic medication phenytoin for the past 10 years. Average total serum phenytoin level from the year prior was in the normal range. Free phenytoin levels were not routinely monitored, but the one value available was elevated at 5.1 ng/dL. The patient underwent a percutaneous nephrolitomy, ultimately expiring from medical complications after the procedure. Final stone analysis revealed a composition of 35% phenytoin metabolite (5-(para-hydroxyphenyl)-5-phenylhydantoin) and 65% proteinaceous material. An extensive review of literature including PubMed, MedLine, and various internet search engines was performed, searching for any prior reports of urinary calculi formed from phenytoin or its metabolite.

RESULTS

No previous reports of phenytoin or phenytoin metabolite urinary stones were found in the medical literature. Phenytoin has many known ill effects on the genitourinary system including acute interstitial nephritis, nephrotic syndrome, acute renal failure, and priapism. Now we can add urinary lithiasis to the list of its potential adverse effects. This article represents the first report of a phenytoin metabolite urinary stone.

CONCLUSION

A metabolite of the commonly used antiepileptic medication phenytoin can cause clinically relevant urolithiasis leading to significant morbidity and even mortality. Clinicians should have an increased level of suspicion for metabolite stone formation in symptomatic patients taking antiepileptic medications. Further studies on phenytoin metabolism and its potential for inducing urinary lithiasis should be performed.