Lamotrigine and hemodialysis in bipolar disorder: case analysis of dosing strategy with literature review

Redefining the age-specific therapeutic ranges of lamotrigine for patients with epilepsy: A step towards optimizing treatment and increasing cost-effectiveness

OBJECTIVE

The pharmacokinetics of lamotrigine exhibits age-related characteristics. Nevertheless, current evidence regarding the therapeutic range of lamotrigine has been derived almost exclusively from studies in adult patients, and the applicability of this therapeutic range to the pediatric population remains unclear. The purpose of this study was to establish the appropriate age-specific therapeutic ranges of lamotrigine corresponding to adequate clinical responses for patients with epilepsy.

METHODS

This prospective cohort study of therapeutic drug monitoring included 582 Chinese epilepsy patients receiving lamotrigine monotherapy. Patients were divided into three age-related subgroups: (1) toddler and school-age group (2-12 years old, n = 168), (2) adolescent group (12-18 years old, n = 171), and (3) adult group (>18 years old, n = 243). Patients with a reduction in seizure frequency of 50 % or greater than baseline were defined as responders, and the remaining patients were non-responders. The relationship between lamotrigine serum concentrations and clinical response was assessed using multivariate logistic regression analysis. A receiver operating characteristic curve was generated to determine the representative cut-off values of lamotrigine trough levels, to distinguish responders from non-responders. The upper margin of the therapeutic range of lamotrigine was determined by developing concentration-effect curves for the three age-related subgroups.

RESULTS

The median trough levels of lamotrigine were significantly higher in responders than in non-responders from all three age-related groups (P < 0.0001). Results of logistic regression analysis revealed that higher serum concentrations of lamotrigine predicted a higher probability that seizure frequency would be reduced by more than 50 % compared to baseline (adjusted odds ratio: 1.228, 95 % CI: 1.137-1.327; P < 0.0001), and younger children were less likely to be responders (adjusted odds ratio: 1.027, 95 % CI: 1.012-1.043; P = 0.001). Based on a trade-off between sensitivity and specificity, the optimal cut-off values for lamotrigine trough concentrations corresponding to clinical response were 3.29 mg/L, 2.06 mg/L, and 1.61 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. By reducing interpatient variability, the results of the concentration-effect curves suggested no additional clinical benefit from a continued increase of doses for lamotrigine concentrations exceeding 9.08 mg/L, 8.43 mg/L, and 10.38 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. In conclusion, the therapeutic ranges of lamotrigine trough concentrations corresponding to adequate clinical response were 3.29-9.08 mg/L in the toddler and school-age group, 2.06-8.43 mg/L in the adolescent group, and 1.61-10.38 mg/L in the adult group.

CONCLUSIONS

The study determined age-specific therapeutic ranges corresponding to optimal clinical efficacy for lamotrigine. Our findings lay the foundation for catalyzing novel opportunities to optimize treatment and reduce therapeutic costs. Based on the age-specific therapeutic ranges identified in this study, individualized and cost-effective algorithms for lamotrigine treatment of epilepsy patients may be developed and validated in larger cohort studies of therapeutic drug monitoring.

Determination of lamotrigine in human plasma using liquid chromatography-tandem mass spectrometry

Aim

Lamotrigine (LTG) is a widely used anti‐epileptic drug that is administered to avoid seizures and to maintain seizure‐free status. However, several factors reportedly cause individual differences of plasma LTG levels, and the therapeutic target range of LTG varies between individuals. Thus, to optimize effective doses of LTG, we developed a rapid and simple method for determining plasma LTG concentrations.

Methods

Lamotrigine and the internal standard papaverine were extracted from human plasma using solid‐phase extraction. After filtration, 5‐μL aliquots of final samples were injected into the liquid chromatography‐tandem mass spectrometry instrument and LTG and internal standard were separated using a Cadenza CD‐C18 column (100 × 2 mm, 3 μm) with 0.1% formic acid in water/acetonitrile (2/1, v/v).

Results

The calibration curve was linear from 0.2 to 5.0 μg/mL, and assessments of recovery, intra‐ and inter‐day precision and accuracy, matrix effects, freeze and thaw stability, and long‐term stability demonstrated good reproducibility. Retention times of LTG and internal standard were 1.6 and 2.0 minutes, respectively, and the total run time was 3.5 minutes for each sample.

Conclusion

We developed a rapid and simple method for determining plasma LTG concentrations. The present novel system could be used to inform LTG dose adjustments for individual patients.

We developed a rapid and simple method for determining plasma concentrations of LTG showing good validation for a relatively wide range (0.2‐5.0 μg/mL). The present method can inform estimates of plasma concentrations of LTG to clinicians within 1 hour of sample collection.

An Updated Overview on Therapeutic Drug Monitoring of Recent Antiepileptic Drugs

Given the distinctive characteristics of both epilepsy and antiepileptic drugs (AEDs), therapeutic drug monitoring (TDM) can make a significant contribution to the field of epilepsy. The measurement and interpretation of serum drug concentrations can be of benefit in the treatment of uncontrollable seizures and in cases of clinical toxicity; it can aid in the individualization of therapy and in adjusting for variable or nonlinear pharmacokinetics; and can be useful in special populations such as pregnancy. This review examines the potential for TDM of newer AEDs such as eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, perampanel, pregabalin, rufinamide, retigabine, stiripentol, tiagabine, topiramate, vigabatrin, and zonisamide. We describe the relationships between serum drug concentration, clinical effect, and adverse drug reactions for each AED as well as the different analytical methods used for serum drug quantification. We discuss retrospective studies and prospective data on the serum drug concentration-efficacy of these drugs and present the pharmacokinetic parameters, oral bioavailability, reference concentration range, and active metabolites of newer AEDs. Limited data are available for recent AEDs, and we discuss the connection between drug concentrations in terms of clinical efficacy and nonresponse. Although we do not propose routine TDM, serum drug measurement can play a beneficial role in patient management and treatment individualization. Standardized studies designed to assess, in particular, concentration-efficacy-toxicity relationships for recent AEDs are urgently required.

Antiepileptic dosing for critically ill adult patients receiving renal replacement therapy

OBJECTIVES

The aim of this review was to evaluate current literature for dosing recommendations for the use of antiepileptic medications in patients receiving renal replacement therapy (RRT).

DATA SOURCES

With the assistance of an experienced medical librarian specialized in pharmacy and toxicology, we searched MEDLINE, EMBASE, CINAHL, Web of Science, WorldCat, and Scopus through May 2016.

STUDY SELECTION AND DATA EXTRACTION

Four hundred three articles were screened for inclusion, of which 130 were identified as potentially relevant. Micromedex® DRUGDEX as well as package inserts were used to obtain known pharmacokinetic properties and dosage adjustment recommendations in RRT if known.

DATA SYNTHESIS

Data regarding antiepileptic drug use in RRT are limited and mostly consist of case reports limiting our proposed dosing recommendations. Known pharmacokinetic parameters should guide dosing, and recommendations are provided where possible.

CONCLUSION

Additional studies are necessary before specific dosing recommendations can be made for most antiepileptic drugs in critically ill patients receiving RRT, specifically with newer agents.

Evolving Electrocardiographic Changes in Lamotrigine Overdose: A Case Report and Literature Review

Lamotrigine overdose usually follows a benign pattern, and the majority of cases reported involve a co-ingestant. Prior reports have suggested the possible use of intravenous lipid emulsion in cases of severe sodium channel blockade. We describe the electrocardiographic changes in a massive lamotrigine overdose treated with intravenous lipid emulsion. A 36-year-old male with bipolar disorder ingested 13.5 g of lamotrigine in a suicidal attempt. The lamotrigine level was 78.0 μg/mL. Comprehensive drug screen was negative for all screened compounds. The electrocardiogram demonstrated a prolonged QRS complex and signs suggestive of sodium channel blockade. Refractory to treatment with sodium bicarbonate was treated with intravenous lipid emulsion, with immediate resolution of the electrocardiographic changes. Lamotrigine inhibits the voltage-gated sodium channel opening, attenuating the release of excitatory neurotransmitters. Cardiac intraventricular conduction could be delayed in cases of lamotrigine overdose resulting in QRS and QTc prolongation and R waves >3 mm in leads I and aVR. A potential role for intravenous lipid emulsion therapy has been described in patients with toxic levels of lamotrigine and electrocardiographic changes refractory to the treatment with sodium bicarbonate. Intravenous lipid emulsion has been successfully used in the treatment of lamotrigine cardiac toxicity.

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.

Severe sodium channel blockade and cardiovascular collapse due to a massive lamotrigine overdose

BACKGROUND

Cardiac arrest due to lamotrigine (LTG) has been reported after co-ingestion with bupropion, but severe sodium channel blockade in the absence of other toxins has not been described. We report a case of cardiac arrest and status epilepticus following a massive LTG overdose.

CASE REPORT

A 48 year-old female was brought to the ED with seizure-like activity subsequent to ingesting 7.5 g of LTG. Vital signs were HR 131, BP 107/68, T 99.4°F, RR 16. She was intubated in the ED for a low GCS. Initial ECG demonstrated a narrow-complex normal sinus rhythm, and her labs were unremarkable. Three hours after intubation she developed status epilepticus, and a pulseless wide-complex tachycardia. She was aggressively resuscitated during which time pulses were periodically reestablished, but lost each time seizures recurred. She was not stabilized until the convulsions were terminated with vecuronium. Her post-resuscitation ECG demonstrated a junctional tachycardia with a 3 mm R-wave in aVR. The LTG level was 74.7 mcg/ml (therapeutic: 3-14 mcg/ml). Comprehensive LC-MS/MS drug screen was negative for all screened compounds.

DISCUSSION

This is the first report of cardiovascular collapse due to LTG with the highest drug concentration to date.

CONCLUSION

The degree of neurologic and cardiovascular toxicity seen in this case are novel and illustrate the potential for severe sodium channel blockade after massive LTG poisonings. Drug levels are not clinically relevant in the acute setting due to the time delay in obtaining results, and recurrent seizure activity may be the only clinical finding that precedes severe cardiac toxicity.