Epidemiology, pathophysiology and putative genetic basis of carbamazepine- and oxcarbazepine-induced hyponatremia

Hyponatremia With Anticonvulsant Medications: A Narrative Review

Hyponatremia is an adverse effect of many antiseizure medications (ASMs). It occurs with interference with the normal balance of electrolytes within the body. Various risk factors associated with the development of hyponatremia in patients taking these medications include age, gender, dosage, and combinations with other drugs. ASMs such as carbamazepine (CBZ), oxcarbazepine (OXC), and valproic acid have a higher risk of hyponatremia. Hyponatremia induced by an antiseizure medication can occur through various mechanisms depending on the drug's specific mechanism of action. Hyponatremia can be a potentially fatal side effect. Patients taking these medications need to be monitored closely for the signs and symptoms of hyponatremia. Acute hyponatremia, defined as developing in <48 hours, is more likely to show symptoms than chronic hyponatremia. Signs of acute hyponatremia include delirium, seizures, decerebrate posturing, and cerebral edema with uncal herniation. Chronic hyponatremia, defined as developing in >48 hours, can cause lethargy, dizziness, weakness, headache, nausea, and confusion. Hyponatremia is associated with longer hospital stays and increased mortality. Treatment varies based on the degree of severity of hyponatremia. Choosing a treatment option should include consideration of the drug causing the electrolyte disturbance, the patient's risk factor profile, and the severity of symptoms as they present in the individual patient. Healthcare providers should be aware of hyponatremia as a potential side effect of ASMs, the signs and symptoms of hyponatremia, the different treatment options available, and the potential complications associated with rapid correction of hyponatremia.

The potential impact of CYP2D6 (*2/*4/*10) gene variants among Egyptian epileptic children: A preliminary study

BACKGROUND

The cytochrome P450 (CYP) isoenzymes have an indispensable role in the metabolic phase of different medications during the treatment of multiple neuropsychiatric disorders. The foremost goal of this study is to evaluate the correlation of the allelic variants within CYP2D6 (*2/*4/*10) gene with the susceptibility for epileptic syndrome as well as the assessment the degree of resistance towards antiepileptic drugs (AEDs).

METHODS

This work was designed based on the involvement of 200 participants [100 unrelated healthy controls, 50 AEDs responsive, and 50 AEDs resistant]. Genomic DNA for the CYP2D6 variants was genotyped utilizing the T-ARMS-PCR technique.

RESULTS

The distributions of the CYP2D6*2 (rs16947; c.886C > T) and CYP2D6*4 (rs3892097; c.506-1G > A) variants were significantly correlated with elevated risk among epileptic patients compared to healthy controls (P-value < 0.05). Furthermore, the CYP2D6*2 variant was statistically associated with disease risk among AEDs responsive patients, while the CYP2D6*4 variant was statistically correlated with disease risk among AEDs resistant patients (P-value < 0.05). Interestingly, the allelic variants of the CYP2D6*4 (A allele) and CYP2D6*10 (T allele) were associated with elevated risk among AEDs resistant compared to AEDs responsive patients (P-value = 0.008 and 0.040, respectively).

CONCLUSIONS

The CYP2D6*2 and CYP2D6*4 variants were recognized as independent risk factors among epileptic patients, but not the CYP2D6*10 variant.

Characterization in Inhibitory Effectiveness of Carbamazepine in Voltage-Gated Na+ and Erg-Mediated K+ Currents in a Mouse Neural Crest-Derived (Neuro-2a) Cell Line

Carbamazepine (CBZ, Tegretol^®) is an anticonvulsant used in the treatment of epilepsy and neuropathic pain; however, several unwanted effects of this drug have been noticed. Therefore, the regulatory actions of CBZ on ionic currents in electrically excitable cells need to be reappraised, although its efficacy in suppressing voltage-gated Na⁺ current (I_Na) has been disclosed. This study was undertaken to explore the modifications produced by CBZ on ionic currents (e.g., I_Na and erg-mediated K⁺ current [I_K(erg)]) measured from Neuro-2a (N2a) cells. In these cells, we found that this drug differentially suppressed the peak (transient, I_Na(T)) and sustained (late, I_Na(L)) components of I_Na in a concentration-dependent manner with effective IC₅₀ of 56 and 18 μM, respectively. The overall current–voltage relationship of I_Na(T) with or without the addition of CBZ remained unchanged; however, the strength (i.e., ∆area) in the window component of I_Na (I_Na(W)) evoked by the short ascending ramp pulse (V_ramp) was overly lessened in the CBZ presence. Tefluthrin (Tef), a synthetic pyrethroid, known to stimulate I_Na, augmented the strength of the voltage-dependent hysteresis (Hys_(V)) of persistent I_Na (I_Na(P)) in response to the isosceles-triangular V_ramp; moreover, further application of CBZ attenuated Tef-mediated accentuation of I_Na(P)’s Hys_(V). With a two-step voltage protocol, the recovery of I_Na(T) inactivation seen in Neuro-2a cells became progressively slowed by adding CBZ; however, the cumulative inhibition of I_Na(T) evoked by pulse train stimulation was enhanced during exposure to this drug. Neuro-2a-cell exposure to CBZ (100 μM), the magnitude of erg-mediated K⁺ current measured throughout the entire voltage-clamp steps applied was mildly inhibited. The docking results regarding the interaction of CBZ and voltage-gate Na⁺ (Na_V) channel predicted the ability of CBZ to bind to some amino-acid residues in Na_V due to the existence of a hydrogen bond or hydrophobic contact. It is conceivable from the current investigations that the I_Na (I_Na(T), I_Na(L), I_Na(W), and I_Na(P)) residing in Neuro-2a cells are susceptible to being suppressed by CBZ, and that its block on I_Na(L) is larger than that on I_Na(T). Collectively, the magnitude and gating of Na_V channels produced by the CBZ presence might have an impact on its anticonvulsant and analgesic effects occurring in vivo.

Oxcarbazepine and Hyponatremia

Background and Objectives: Hyponatremia is one of the most common adverse effects in patients treated with oxcarbazepine (OXC). Different risk factors for OXC-induced hyponatremia have been described as age, female gender, dosage, and combination with other drugs During our clinical practice, we noticed that a longer duration of treatment with OXC could be associated with a higher risk of hyponatremia, therefore, in this study, we aimed to evaluate factors that may increase the risk of OXC-induced hyponatremia. Materials and Methods: Data were retrospectively collected from our clinical database at the Department of Neurology of the Hospital of Lithuanian University of Health Sciences Kaunas Clinics. The sample was divided into three groups: OXC consumers (n = 31), other anti-seizure medications (ASMs) consumers (n = 43), and controls absent ASMs (n = 31). All groups were matched by age and gender. Hyponatremia was defined as <136 mmol/L. Results: The frequency of hyponatremia was significantly higher among OXC patients (61.3%) compared to other ASM patients (5.4%) and controls (3.2%). The mean serum sodium concentration in the OXC group was 133.1 ± 5.1 mmol/L. The frequency of severe hyponatremia among OXC-treated patients was 19.4%; this subgroup was older than patients with moderate hyponatremia and normonatremia and had a longer OXC treatment duration compared to a subgroup of normonatremia. The average duration of OXC therapy was 8.7 ± 5.5 years with a range from 1 to 21 years. Serum sodium concentration and duration of treatment with OXC demonstrated a significant negative correlation (r = −0,427, p = 0.017). Each year of therapy with OXC increased the risk of hyponatremia 1.3 times (OR = 1.326, 95% Cl 1.027−1.712, p = 0.031). Other factors (gender, age, polypharmacy, OXC dosage, and serum concentration) did not show a significant association with the development of hyponatremia. Conclusions: Longer duration of treatment with OXC is an important factor in the development and severity of hyponatremia.

Eslicarbazepine-induced severe hyponatremia resulted in generalized tonic-clonic seizure

Although eslicarbazepine is an anti-seizure medication, it may result in seizure worsening if its use is complicated by severe hyponatremia, even long time after commencing this medication. The treatment is a replacement for another ASM.

Oxcarbazepine for Behavioral Disorders after Brain Injury: Factors Influencing Efficacy

Carbamazepine and oxcarbazepine are used for behavioral disorders following organic diseases. After severe acquired brain injury, patients may develop frontal symptoms. In our neurological rehabilitation routine, oxcarbazepine is used for better safety over carbamazepine, although its efficacy is not clarified. We aimed to improve knowledge on this use of oxcarbazepine, by probing clinical factors associated with response. We retrospectively examined the clinical records of our patients, collecting clinical variables and outcomes of efficacy, both clinician-rated and caregiver/self-rated. We described the distribution of clinical variables and examined their associations via logistic regressions. Patients in our cohort were predominantly pediatric, with frontal lobe damage and irritable/reactive. With an oxcarbazepine median dose of 975 mg, almost half of patients improved. We found several clinical factors associated with clinician-rated efficacy: absence of frontal damage and absence of irritability/reactivity symptoms; clinical factors associated with caregivers/patients-rated efficacy were: higher DRS score at baseline and higher patient age. In this retrospective study, we observed that oxcarbazepine was differentially efficacious in patients with specific characteristics. Our study could not examine drug therapy separately from neuropsychological therapy, nor the influence of dose. Our associative results should be verified experimentally, also assessing causality and establishing dose-related efficacy and safety.

Psychotropic drugs upregulate aquaporin-2 via vasopressin-2 receptor/cAMP/protein kinase A signaling in inner medullary collecting duct cells

Psychotropic drugs may be associated with hyponatremia, but an understanding of how they induce water retention in the kidney remains elusive. Previous studies have postulated that they may increase vasopressin production in the hypothalamus without supporting evidence. In this study, we investigated the possibility of drug-induced nephrogenic syndrome of inappropriate antidiuresis using haloperidol, sertraline, and carbamazepine. Haloperidol, sertraline, or carbamazepine were treated in inner medullary collecting duct (IMCD) suspensions and primary cultured IMCD cells prepared from male Sprague-Dawley rats. The responses of intracellular cAMP production, aquaporin-2 (AQP2) protein expression and localization, vasopressin-2 receptor (V2R) and AQP2 mRNA, and cAMP-responsive element-binding protein (CREB) were tested with and without tolvaptan and the protein kinase A (PKA) inhibitors H89 and Rp-cAMPS. In IMCD suspensions, cAMP production was increased by haloperidol, sertraline, or carbamazepine and was relieved by tolvaptan cotreatment. In primary cultured IMCD cells, haloperidol, sertraline, or carbamazepine treatment increased total AQP2 and decreased phosphorylated Ser261-AQP2 protein expression. Notably, these responses were reversed by cotreatment with tolvaptan or a PKA inhibitor. AQP2 membrane trafficking was induced by haloperidol, sertraline, or carbamazepine and was also blocked by cotreatment with tolvaptan or a PKA inhibitor. Furthermore, upregulation of V2R and AQP2 mRNA and phosphorylated CREB was induced by haloperidol, sertraline, or carbamazepine and was blocked by tolvaptan cotreatment. We conclude that, in the rat IMCD, psychotropic drugs upregulate AQP2 via V2R-cAMP-PKA signaling in the absence of vasopressin stimulation. The vasopressin-like action on the kidney appears to accelerate AQP2 transcription and dephosphorylate AQP2 at Ser261.NEW & NOTEWORTHY It is unclear whether antipsychotic drugs can retain water in the kidney in the absence of vasopressin. This study demonstrates that haloperidol, sertraline, and carbamazepine can produce nephrogenic syndrome of inappropriate antidiuresis because they directly upregulate vasopressin-2 receptor and aquaporin-2 (AQP2) via cAMP/PKA signaling. We showed that, in addition to AQP2 trafficking, AQP2 protein abundance was rapidly increased by treatment with antipsychotic drugs in association with dephosphorylation of AQP2 at Ser261 and accelerated AQP2 transcription.

[The efficacy and tolerability of extended release carbamazepine in adult patients with new-onset epilepsy using epileptiform activity index]

OBJECTIVE

To evaluate the efficacy and tolerability of extended release carbamazepine (finlepsin-retard and tegretol CR) in adult patients with new-onset focal epilepsy (FE) with the assessment of epileptiform activity index (EAI).

MATERIAL AND METHODS

The study included 62 patients (38 (61.3%) men and 24 (38.7%) women) with new-onset FE aged ≥18 years (mean age 42.9±18.4 years). All patients underwent video-ECG-monitoring with EAI assessment at each visit. Treatment efficacy was assessed using the criteria of seizure absence (medically induced remission), seizure rate decrease by >50% (responders), seizure rate decrease by <50% - insufficient efficacy, retention on treatment and seizure rate increase compared to baseline and/or development of new type of seizures (aggravation). Overall study period was 12 months.

RESULTS

By the end of the 12-month follow-up period, there was a 4.3-fold decrease of the total EAI compared to baseline (p<0.001). Retention on carbamazepine treatment during 12 months was achieved in 61.3% (n=38) patients; medically induced remission - in 40.3% (n=25); seizure rate decrease by >50% - in 21.0% (n=13). In 29.1% (n=18) of patients, treatment change was performed; double-drug therapy, including carbamazepine, was prescribed in 9.6% (n=6) of patients. Incidence of adverse events was 29.1% (n=18).

CONCLUSIONS

Carbamazepine is an effective and promising drug for initial monotherapy of FE. Its use in the treatment of FE results in a 4.3-fold decrease of EAI (p<0.001), which reflects the efficacy of treatment. EAI is an additional objective measure of treatment efficacy.

Characteristics and outcome-related factors of seizure at the first onset of autoimmune encephalitis: A retrospective study

Aims

Seizure outcome of autoimmune encephalitis (AE) varies from seizure‐free to refractory epilepsy, and the associated factors remain unclear. We aimed to describe seizure characteristics, identify seizure outcome‐related factors, and discuss the medication strategy of antiepileptic drugs (AEDs) at the first onset of AE.

Methods

We retrospectively studied the data of 86 patients with clinically diagnosed AE. The clinical characteristics were described using a chi‐square test. Seizure outcome‐related factors were assessed using multivariable logistic regression analysis.

Results

56 patients were finally enrolled, with antibodies to N‐methyl‐D‐aspartate receptor found in 29, to γ‐aminobutyric acid receptor B found in 13, and to leucine‐rich glioma‐inactivated protein 1 found in 14. Status epilepticus occurrence and onset with seizure lead to a poor seizure outcome, while administration of human gamma globulin and a low antibody titer contributed to a good seizure outcome.

Conclusions

In the acute phase, seizure characteristics may be considered in the utilization of AEDs. For patients with seizure‐free status in the acute phase, clinical manifestation (onset with seizure or not, whether status epilepticus occurs or not), therapy regimen (human gamma globulin administered or not), and antibody titer may be considered when formulating the strategy for withdrawal of AEDs post‐acute phase.

Symptomatology of carbamazepine- and oxcarbazepine-induced hyponatremia in people with epilepsy

OBJECTIVE

To ascertain whether adverse effects experienced by people taking carbamazepine or oxcarbazepine could be attributed to carbamazepine- or oxcarbazepine-induced hyponatremia (COIH).

METHODS

We performed an observational study, collecting data between 2017 and 2019 on serum sodium levels and adverse effects retrospectively in people with epilepsy while receiving treatment with either carbamazepine (CBZ) or oxcarbazepine (OXC). We defined hyponatremia as sodium level ≤134 mEq/L and severe hyponatremia as sodium level ≤128 mEq/L. Adverse effects experienced were compared between groups of individuals with and without hyponatremia.

RESULTS

A total of 1370 people using CBZ or OXC were identified, of whom 410 had at least one episode of hyponatremia. We checked for symptoms related to the use of CBZ and OXC in 710 people (410 with and 300 without hyponatremia) and found relevant information in 688. Adverse effects occurred in 65% of people with hyponatremia compared to 21% with normal sodium levels (odds ratio [OR] 7.5, P ≤ .001) and in 83% of people with severe hyponatremia compared to 55% in those with mild hyponatremia (P ≤ .001). Significant predictors of adverse effects were the drug (OXC vs CBZ), and the number of concomitant anti-seizure medications. Dizziness (28% vs 6%), tiredness (22% vs 7%), instability (19% vs 3%), and diplopia (16% vs 4%) were reported more often in the hyponatremia group than in patients with normal levels.

SIGNIFICANCE

People with COIH had a 7-fold increased risk of developing adverse effects during treatment. Clinicians should consider ascertainment of sodium levels in patients taking CBZ and OXC and act upon findings.

Analysis of treatment adherence and cost among patients with epilepsy: a four-year retrospective cohort study in Pakistan

BACKGROUND

The adherence pattern of antiepileptic drugs (AEDs) among patients with epilepsy is relatively lower in the United States and different European countries. However, adherence and cost analysis of AEDs in Asian countries have not been thoroughly studied. Therefore, the present study aimed to analyze the cost and adherence of AEDs and its associated factors in patients followed in Pakistan.

METHODS

Data from prescriptions collected from patients with epilepsy who have visited the Outpatient Department (OPD) of different tertiary care hospitals at the cosmopolitan city of Karachi, Pakistan from December 2015 to November 2019. The mean follow-up period for each participant was about 22 months. Pairwise comparisons from Cox regression/hazard ratios were used to assess the predictors of adherence. Direct costs of AEDs were calculated and presented as the annual cost of drugs.

RESULTS

A total of 11,490 patients were included in this study, 51.2 % were male and 48.8 % were female with a mean age of 45.2 ± 15.8 y. Levetiracetam was found as the most prescribing AED in all study participants (32.9 %). Of them, 49.1 % of patients continued their initial recommended treatment. However, 31.3 % of patients have discontinued the therapy, while, 19.6 % were switched to other AED. Adherence with initial treatment was more profound in male (57.4 %) patients, compared to female with a mean age of 44.2 years. Lamotrigine users (60.6 %) showed a higher tendency to retain on initially prescribed drugs. The total cost of epilepsy treatment in the entire study cohort was 153280.5 PKR ($941.9). By applying the Cox regression analysis, it can be observed that the patients with increasing age (OR, 2.04), migraine (OR, 2.21), psychiatric disorders (OR, 4.28), other comorbidities (OR, 1.52) and users of other than top five prescribing AEDs (2.35) were at higher risk of treatment discontinuation. However, levetiracetam (OR, 0.69), valproic acid (OR, 0.52), carbamazepine (OR, 0.81), lamotrigine (OR, 0.80) or lacosamide (OR, 0.65) users have more chances to continue their initial therapy.

CONCLUSIONS

Similar to western countries, the majority of patients with epilepsy exhibited low adherence with AEDs. Various associated factors for improving adherence were identified in this study.

Lithium for Carbamazepine-Induced Syndrome of Inappropriate Antidiuretic Hormone

OBJECTIVES

To examine the effectiveness of low-dose lithium carbonate for managing carbamazepine-induced hyponatremia.

METHODS

Single case study in an 88 year old man with bipolar illness and vascular dementia who had failed to respond to other mood stabilizers.

RESULTS

The patient had developed hyponatremia on two separate occasions when treated with carbamazepine. Introduction of low-dose lithium resulted in prompt normalization of serum sodium levels, which was maintained for the subsequent 8 weeks.

CONCLUSIONS

Carbamazepine may sometimes be the best or only viable treatment option for patients with bipolar illness or other conditions. When its use is complicated by syndrome of inappropriate ADH, dose reduction and fluid restriction are the simplest options but, if ineffective, addition of lithium may be a feasible, albeit somewhat complicated, alternative.

Pharmacokinetic Monitoring of Levetiracetam in Portuguese Refractory Epileptic Patients: Effect of Gender, Weight and Concomitant Therapy

Levetiracetam is a second-generation antiepileptic drug, widely used in the treatment of focal and generalized epilepsy due to its pharmacokinetic and safety profiles. Its pharmacokinetic monitoring is ascribed as useful to personalize its dosing regimen. The aim of the present study was to describe, for the first time, the pharmacokinetics of levetiracetam in Portuguese refractory epileptic patients. Therefore, a retrospective study was carried out on 65 Portuguese refractory epileptic patients (pharmacokinetic study: 48; validation study: 17) admitted to the Refractory Epilepsy Centre of the Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal. The pharmacokinetic parameters of levetiracetam were estimated by applying a one-compartment model with first-order absorption and elimination analysis. Male patients showed higher distribution volume (Vd/F) and oral clearance (CL/F) than female patients (median Vd/F: 52.40 L in males and 38.60 L in females, p = 0.011; median CL/F: 4.71 L/h in males and 3.91 L/h in females, p = 0.028). Higher values of Vd/F (p = 0.026) and CL/F (p = 0.003) were also found in overweight patients relative to normal weight and obese patients. Carbamazepine was the co-administered antiepileptic drug that mostly affected the pharmacokinetics of levetiracetam, increasing both Vd/F (61.30 L with carbamazepine and 39.10 L without carbamazepine, p = 0.007) and CL/F (6.71 L/h with carbamazepine and 3.91 L/h without carbamazepine, p < 0.001). The pharmacokinetics of levetiracetam was affected by gender, body mass index, and co-administration of carbamazepine. This study highlights the impact of several factors on the CL/ and Vd/F of levetiracetam when administered to refractory epileptic patients. The importance of its pharmacokinetic monitoring in clinical pharmacy stands out, thereby enabling the optimization of antiepileptic drug therapy.

Oxcarbazepine for trigeminal neuralgia may induce lower extremity weakness: A case report

BACKGROUND

Although few studies have reported hyponatremia due to carbamazepine or oxcarbazepine in patients with epilepsy, no study has investigated cases of carbamazepine- or oxcarbazepine-induced hyponatremia or unsteady gait in patients with neuropathic pain. Herein, we report a case of oxcarbazepine-induced lower leg weakness in a patient with trigeminal neuralgia and summarize the diagnosis, treatment, and changes of clinical symptoms.

CASE SUMMARY

A 78-year-old male with a history of lumbar spinal stenosis was admitted to the hospital after he experienced lancinating pain around his right cheek, eyes, and lip, and was diagnosed with trigeminal neuralgia at the right maxillary and mandibular branch. He was prescribed oxcarbazepine (600 mg/d), milnacipran (25 mg/d), and oxycodone/naloxone (20 mg/10 mg/d) for four years. Four years later, the patient experienced symptoms associated with spinal stenosis, including pain in the lower extremities and unsteady gait. His serum sodium level was 127 mmol/L. Assuming oxcarbazepine to be the cause of the hyponatremia, oxcarbazepine administration was put on hold and the patient was switched to topiramate. At subsequent visit, the patient’s serum sodium level had normalized to 143 mmol/L and his unsteady gait had improved.

CONCLUSION

Oxcarbazepine-induced hyponatremia may cause lower extremity weakness and unsteady gait, which should be differentiated from those caused by spinal stenosis.

Trigeminal Neuralgia: Basic and Clinical Aspects

The trigeminal nerve is the largest of all cranial nerves. It has three branches that provide the main sensory innervation of the anterior two-thirds of the head and face. Trigeminal neuralgia (TN) is characterized by sudden, severe, brief, and stabbing recurrent episodes of facial pain in one or more branches of the trigeminal nerve. Pain attacks can occur spontaneously or can be triggered by non-noxious stimuli, such as talking, eating, washing the face, brushing teeth, shaving, a light touch or even a cool breeze. In addition to pain attacks, a proportion of the patients also experience persistent background pain, which along with autonomic signs and prolonged disease duration, represent predictors of worse treatment outcomes. It is now widely accepted that the presence of a neurovascular compression at the trigeminal root entry zone is an anatomic abnormality with a high correlation with classical TN. However, TN may be related to other etiologies, thus presenting different and/or additional features. Since the 1960s, the anticonvulsant carbamazepine is the drug of choice for TN treatment. Although anti-epileptic drugs are commonly used to treat neuropathic pain in general, the efficacy of carbamazepine has been largely limited to TN. Carbamazepine, however, is associated with dose-limiting side-effects, particularly with prolonged usage. Thus, a better understanding and new treatment options are urgently warranted for this rare, but excruciating disease.

Prevalence and risk factors for hyponatremia in adult epilepsy patients: Large-scale cross-sectional cohort study

PURPOSE

To evaluate the risk factors and prevalence of hyponatremia among epilepsy patients in relation to use of antiepileptic drugs (AEDs).

METHODS

We retrospectively reviewed 14,620 adult patients (aged 18-103 years) and classified them into the following 3 groups: patients without AED treatment (n = 2165, Group I), patients receiving antiepileptic drugs other than carbamazepine (n = 7442, Group II), and patients treated with carbamazepine (n = 5013, Group III). This study did not include the patients receiving oxcarbazepine or eslicarbazepine acetate because these AEDs are not marketed in Japan. Severe hyponatremia was defined as a serum sodium level < 130 mEq/L.

RESULTS

In Groups I, II, and III, the mean sodium level was 140, 139, and 137 mEq/L, respectively. The highest frequency of severe hyponatremia was observed in Group III (7%), and it was much higher than in Group I (0.8%) or Group II (1.2%). In Groups II and III, old age, low body weight, and concomitant use of phenobarbital, benzodiazepines, or antipsychotics were risk factors for hyponatremia. In Group III, the sodium level decreased as the carbamazepine dose increased. At a carbamazepine dose exceeding 600 mg/day, there was 10.9-fold higher prevalence of hyponatremia, and the risk was potentiated by concomitant use of valproate.

CONCLUSION

The serum sodium level should be monitored carefully when patients are receiving AED polypharmacy combined with antipsychotics. In particular, concomitant administration of valproate enhances the risk of hyperammonemia in patients receiving carbamazepine. These findings may help clinicians to avoid hyponatremia in patients with epilepsy.

Serum sodium levels and related treatment-emergent adverse events during eslicarbazepine acetate use in adults with epilepsy

Objective

To examine the frequency of hyponatremia and potentially related symptoms in clinical trials of eslicarbazepine acetate (ESL) in adults with focal‐ (partial‐) onset seizures.

Methods

This post hoc, exploratory analysis included data from three controlled phase 3 trials of adjunctive ESL (400‐1200 mg once daily), two phase 3 trials of ESL monotherapy (1200‐1600 mg once daily), and their open‐label extension studies. Exploratory endpoints included clinical laboratory measurements of serum sodium concentrations ([Na⁺]), incidences of hyponatremia‐related treatment‐emergent adverse events (TEAEs), and incidences of TEAEs that are potential symptoms of hyponatremia.

Results

The controlled trials of adjunctive ESL and ESL monotherapy included 1447 (placebo, n = 426; ESL, n = 1021) and 365 (ESL, n = 365) patients, respectively; 639 and 274 patients continued onto uncontrolled, open‐label extensions. In the controlled and uncontrolled trials ≤3.3% of patients taking ESL had a minimum postdose [Na⁺] measurement ≤125 mEq/L, <9% had a >10 mEq/L decrease in [Na⁺] from baseline, <6% had a hyponatremia‐related TEAE, and <2% discontinued the controlled trials due to a hyponatremia‐related TEAE. Hyponatremia appeared to be more frequent in the monotherapy (vs adjunctive therapy) trials; in the controlled trials of adjunctive ESL and ESL monotherapy, incidence generally increased with increasing ESL dose. The majority of patients with an investigator‐reported TEAE of “hyponatremia” or “blood sodium decreased” did not have a corresponding laboratory [Na⁺] measurement ≤125 mEq/L. Some symptoms potentially related to hyponatremia (including nausea and vomiting) were more frequent in patients with a minimum postdose [Na⁺] measurement ≤125 mEq/L.

Significance

Reductions in serum sodium concentrations and hyponatremia‐related TEAEs occurred in a small number of patients taking ESL. Suspected hyponatremia should be confirmed and monitored via [Na⁺] measurements.

Antiepileptic drug therapy in the elderly: a clinical pharmacological review

Seizure disorder is the third most common neurological disorder in the elderly after stroke and dementia. With the increasing geriatric population, the situation of clinicians seeing more and more elderly epilepsy patients is very likely. Not only is the diagnosis of epilepsy tedious in the elderly, its management raises many challenging issues for the treating physicians. Altered physiology, age-related decline in organ function, and plasma protein binding and altered pharmacodynamics make the elderly patients with seizure disorder a difficult group to treat. This is further complicated by the presence of comorbidities and polypharmacy which increase the chances of drug interactions. The adverse effects that might be tolerated well in younger populations may be disastrous for the aged. Although the newer antiepileptic drugs are found to have a favorable safety profile, there is relative scarcity of randomized-controlled trials involving older and newer antiepileptics in the geriatric population. This review tries to compile the available literature on management of epilepsy in the elderly population including evidence of safety and efficacy of newer and older antiepileptics with special reference to the 'geriatric giants'. It also deals with the interactions between antiepileptic medications and other commonly prescribed drugs in the elderly such as anti-hypertensives and antiischemic agents. The recommended guidelines of various international bodies are also analyzed from the perspective of elderly with seizure disorder.

A genome-wide association study of sodium levels and drug metabolism in an epilepsy cohort treated with carbamazepine and oxcarbazepine

OBJECTIVE

To ascertain the clinical and genetic factors contributing to carbamazepine- and oxcarbazepine-induced hyponatremia (COIH), and to carbamazepine (CBZ) metabolism, in a retrospectively collected, cross-sectional cohort of people with epilepsy.

METHODS

We collected data on serum sodium levels and antiepileptic drug levels in people with epilepsy attending a tertiary epilepsy center while on treatment with CBZ or OXC. We defined hyponatremia as Na+ ≤134 mEq/L. We estimated the CBZ metabolic ratio defined as the log transformation of the ratio of metabolite CBZ-diol to unchanged drug precursor substrate as measured in serum.

RESULTS

Clinical and genetic data relating to carbamazepine and oxcarbazepine trials were collected in 1141 patients. We did not observe any genome-wide significant associations with sodium level in a linear trend or hyponatremia as a dichotomous trait. Age, sex, number of comedications, phenytoin use, phenobarbital use, and sodium valproate use were significant predictors of CBZ metabolic ratio. No genome-wide significant associations with CBZ metabolic ratio were found.

SIGNIFICANCE

Although we did not detect a genetic predictor of hyponatremia or CBZ metabolism in our cohort, our findings suggest that the determinants of CBZ metabolism are multifactorial.

Acute hyponatremia with accompanying hyperammonemia secondary to divalproex sodium: A case report

Divalproex sodium (DVP) is an antiepileptic medication that also has mood stabilizing properties for patients with mental health disorders. Currently, there are a small number of case reports discussing the incidence of hyponatremia that occurs as an adverse effect of DVP. After completion of a thorough literature search, we present the first case report describing acute hyponatremia with accompanying hyperammonemia secondary to DVP use. This case describes a 44-year-old male patient who experienced hyponatremia with accompanying hyperammonemia following initiation of DVP for schizoaffective disorder. This case highlights the need for clinicians to consider monitoring electrolytes, in addition to liver function and platelets, with the initiation of therapy or increase in daily dosage. Given the drug's action at voltage-gated sodium channels, changes in serum sodium could be expected.

Eslicarbazepine Acetate: A New Improvement on a Classic Drug Family for the Treatment of Partial-Onset Seizures

Eslicarbazepine acetate is a new anti-epileptic drug belonging to the dibenzazepine carboxamide family that is currently approved as adjunctive therapy and monotherapy for partial-onset (focal) seizures. The drug enhances slow inactivation of voltage-gated sodium channels and subsequently reduces the activity of rapidly firing neurons. Eslicarbazepine acetate has few, but some, drug–drug interactions. It is a weak enzyme inducer and it inhibits cytochrome P450 2C19, but it affects a smaller assortment of enzymes than carbamazepine. Clinical studies using eslicarbazepine acetate as adjunctive treatment or monotherapy have demonstrated its efficacy in patients with refractory or newly diagnosed focal seizures. The drug is generally well tolerated, and the most common side effects include dizziness, headache, and diplopia. One of the greatest strengths of eslicarbazepine acetate is its ability to be administered only once per day. Eslicarbazepine acetate has many advantages over older anti-epileptic drugs, and it should be strongly considered when treating patients with partial-onset epilepsy.

Carbamazepine adverse drug reactions

INTRODUCTION

Carbamazepine (CBZ) is used for the treatment of epilepsy and other neurological and psychiatric disorders. The occurrence of adverse reactions (ADRs) to CBZ can negatively impact the quality of life of patients, as well as increase health-care costs. Thus, knowledge of CBZ-induced ADRs is important to achieve safer treatment outcomes. Areas covered: This review describes the clinical features, known mechanisms, and clinical management of the main CBZ-induced ADRs. In addition, pharmacogenetic studies focused on ADRs induced by CBZ are cited. Expert commentary: CBZ-induced ADRs are well known in the literature. The metabolite CBZ-10,11-epoxide plays an important role in the mechanism that underlies the ADRs induced by CBZ. Several factors should be considered for a safer use of CBZ, such as monotherapy prescription when possible, an adequate dose titration, knowledge of previous ADRs in the patient, and routine monitoring of CBZ plasma concentrations in symptomatic patients. Pharmacogenetics is a potential tool for CBZ therapy improvement, and the design of multicenter studies focused on the identification of biomarkers for CBZ-induced ADRs could provide useful information for a safer CBZ therapy.

Differences in associations of antiepileptic drugs and hospitalization due to hyponatremia: A population-based case-control study

PURPOSE

Hyponatremia induced by antiepileptic drugs is common, but detailed evidence is lacking. This can be problematic for the treating neurologist confronted with a patient with severe hyponatremia in need of an alternative drug. The objective of this study was to examine the association between individual antiepileptic drugs and hospitalization due to hyponatremia.

METHODS

This was a register-based case-control study of patients in the general Swedish population. We included 14,359 individuals with a principal diagnosis of hyponatremia and 57,383 matched controls. The association between newly initiated (≤90 days) and ongoing antiepileptic treatment was investigated using multivariable logistic regression adjusting for concomitant drugs, medical conditions, previous hospitalizations and sociaoeconomic factors.

RESULTS

For newly initiated antiepileptic drugs, adjusted ORs (95% CI) for hospitalization due to hyponatremia, compared to controls, were: carbamazepine 9.63 (6.18-15.33); phenytoin 4.83 (1.14-25.76); valproate 4.96 (2.44-10.66); lamotrigine 1.67 (0.70-4.08); levetiracetam 9.76 (4.02-27.59) and gabapentin 1.61 (1.08-2.38). Newly initiated oxcarbazepine treatment was only found in the hyponatremia group and not in controls. Adjusted ORs (CI) for individuals with ongoing treatment ranged from 7.97 (3.70-18.50) for oxcarbazepine to 0.83 (0.64-1.06) for gabapentin.

CONCLUSION

There was a strong association between newly initiated treatment with carbamazepine, oxcarbazepine and levetiracetam, and hospitalization due to hyponatremia. The corresponding association for phenytoin and valproate was moderate. The risk for hyponatremia was lower during ongoing treatment. Lamotrigine and gabapentin had the lowest risk both during initiation and ongoing treatment and may be advantageous in patients at risk of developing hyponatremia.

Antiepileptic drugs-induced hyponatremia: Review and analysis of 560 hospitalized patients

Recent evidence suggests that eslicarbazepine acetate (ESL) might be an appropriate alternative to carbamazepine (CBZ) and oxcarbazepine (OXC) due to its better safety profile. Hyponatremia may be one of the limiting safety problems in CBZ and OXC whereas it has been indicated that ESL is less sensitive for the adverse event. Since our clinical experience is different we investigated the incidence of hyponatremia in 560 consecutive adult inpatients treated at our center in 2015 by reviewing their medical records. Only CBZ, OXC and ESL were associated with hyponatremia. The incidence of hyponatremia induced by ESL was not statistically different from that induced by OXC (43% of patients with OXC and 33% with ESL, p > 0.05). Both were associated with hyponatremia more often than CBZ (16%). OXC-induced hyponatremia was dose-related, ESL-induced hyponatremia was not. Furthermore, both OXC- and ESL-induced hyponatremia occurred particularly often in elderly epilepsy patients. Thus, for elderly patients, both OXC and ESL should be considered with caution.

Carbamazepine- and oxcarbazepine-induced hyponatremia in people with epilepsy

OBJECTIVE

To ascertain possible determinants of carbamazepine (CBZ)- and oxcarbazepine (OXC)-induced hyponatremia in a large cohort of people with epilepsy.

METHODS

We collected data on serum sodium levels in people with epilepsy who were attending a tertiary epilepsy center while on treatment with CBZ or OXC. We defined hyponatremia as Na+ ≤134 mEq/L and severe hyponatremia as Na+ ≤128 mEq/L.

RESULTS

We identified 1,782 people who had used CBZ (n = 1,424) or OXC (n = 358), of whom 50 were treated with both drugs. Data on sodium level measurements were available in 1,132 on CBZ and in 289 on OXC. Hyponatremia occurred in 26% of those taking CBZ and 46% of those taking OXC. This was severe in 7% in the CBZ group and 22% in the OXC group. Hyponatremia was symptomatic in 48% and led to admissions in 3%. Age over 40 years, high serum levels of CBZ and OXC, and concomitant use of other antiepileptic drugs were the main risk factors for hyponatremia in both treatment groups. Female patients on OXC were at a higher risk than male patients of hyponatremia. The risk of hyponatremia on CBZ was significantly associated with the risk of hyponatremia on OXC within a subgroup that used both drugs consecutively.

SIGNIFICANCE

Hyponatremia is a common problem in people taking CBZ or OXC. Regular ascertainment of sodium levels in those taking either drug is recommended and results should be acted on.

Turning down the volume: Astrocyte volume change in the generation and termination of epileptic seizures

Approximately 1% of the global population suffers from epilepsy, a class of disorders characterized by recurrent and unpredictable seizures. Of these cases roughly one-third are refractory to current antiepileptic drugs, which typically target neuronal excitability directly. The events leading to seizure generation and epileptogenesis remain largely unknown, hindering development of new treatments. Some recent experimental models of epilepsy have provided compelling evidence that glial cells, especially astrocytes, could be central to seizure development. One of the proposed mechanisms for astrocyte involvement in seizures is astrocyte swelling, which may promote pathological neuronal firing and synchrony through reduction of the extracellular space and elevated glutamate concentrations. In this review, we discuss the common conditions under which astrocytes swell, the resultant effects on neural excitability, and how seizure development may ultimately be influenced by these effects.

Antipsychotic use is a risk factor for hyponatremia in patients with schizophrenia: a 15-year follow-up study

RATIONALE

Hyponatremia affects 10% of patients with chronic schizophrenia and can lead to severe consequences. However, the role of antipsychotics and other risk factors in hyponatremia occurrence has remained inconsistent.

OBJECTIVE

This study examined the association between antipsychotic use and hyponatremia occurrence in patients with schizophrenia.

METHODS

We utilized the National Health Insurance Research Database to follow 2051 patients with schizophrenia from 1998 to 2013. Among them, 137 (6.7%) developed hyponatremia. Sociodemographic characteristics, physical comorbidities, and psychiatric treatment experiences were compared between those who had hyponatremia and those who did not. A Cox proportional hazards model was used to examine the hazard ratios (HRs) of these characteristics.

RESULTS

In patients with hyponatremia, the mean age at first hyponatremia occurrence was 54.7 ± 13.9 years, an average of 9.5 ± 4.0 years after schizophrenia diagnosis, and 32.9% of them were off antipsychotics before hyponatremia occurrences. Age at schizophrenia diagnosis (HR = 1.1), low-income household (HR = 2.4), comorbidities (HR = 1.2), and psychiatric admissions (HR = 1.04) were associated with the risks of hyponatremia. Compared with no antipsychotic use, atypical (HR = 2.1) and typical antipsychotics (HR = 3.1) were associated with an elevated risk of hyponatremia, after adjustment for age, sex, and physical comorbidities. Carbamazepine use (HR = 2.9) was also a significant risk factor for hyponatremia (p < 0.05).

CONCLUSIONS

Antipsychotic use in patients with schizophrenia with polypharmacy should be monitored for hyponatremia occurrences. Clinicians should pay attention to the impact of poor living conditions on hyponatremia occurrence.

Pharmacokinetic variability, efficacy and tolerability of eslicarbazepine acetate-A national approach to the evaluation of therapeutic drug monitoring data and clinical outcome

BACKGROUND

Eslicarbazepine acetate (ESL) is a new antiepileptic drug (AED), still insufficiently studied regarding pharmacokinetic variability, efficacy and tolerability. The purpose of this study was to evaluate therapeutic drug monitoring (TDM) data in Norway and relate pharmacokinetic variability to clinical efficacy and tolerability in a long-term clinical setting in patients with refractory epilepsy.

METHODS

This retrospective observational study included TDM-data from the main laboratories and population data from the Norwegian Prescription Database in Norway, in addition to clinical data from medical records of adult patients using ESL for up to three years, whenever possible.

RESULTS

TDM-data from 168 patients were utilized for assessment of pharmacokinetic variability, consisting of 71% of the total number of patients in Norway using ESL, 2011-14. Median daily dose of ESL was 800mg (range 400-1600mg), and median serum concentration of ESL was 53μmol/L (range 13-132μmol/L). Inter-patient variability of ESL was extensive, with 25-fold variability in concentration/dose ratios. Additional clinical data were available from 104 adult patients out of the 168, all with drug resistant focal epilepsy. After 1, 2 and 3 years follow-up, the retention rate of ESL was 83%, 72% and 64%, respectively. ESL was generally well tolerated as add-on treatment, but sedation, cognitive impairment and hyponatremia were reported. Hyponatremia (sodium <137mmol/L) was present in 36% of the patients, and lead to discontinuation in three.

CONCLUSION

Pharmacokinetic variability of ESL was extensive and the demonstration of usefulness of TDM requires further studies. In patients with drug resistant focal Epilepsy, the high retention rate indicated good efficacy and tolerability. Hyponatremia was observed in one third of the patients. The present results point to a need for individualization of treatment and TDM may be useful.

Hyponatremia induced by antiepileptic drugs in patients with epilepsy

INTRODUCTION

Hyponatremia induced by antiepileptic drugs (AEDs) has not received sufficient attention in patients with epilepsy. Areas covered: We reviewed articles between 1966 and 2015 about hyponatremia as an adverse effect of AEDs in patients with epilepsy. The incidence, clinical symptoms, onset times of AEDs-induced hyponatremia are discussed in detail, as are the risk factors associated with AEDs-induced hyponatremia and mechanisms underlying its development. We also briefly describe strategies for treating AED-induced hyponatremia. Expert opinion: Carbamazepine and oxcarbazepine are the most common AEDs which induce hyponatremia in patients with epilepsy. Recently, other AEDs, such as eslicarbazepine, sodium valproate, lamotrigine, levetiracetam and gabapentin have also been reported to cause hyponatremia. Understanding the risk associated with AED-induced hyponatremia and taking effective measures to combat serum sodium imbalance induced by AED therapy are necessary.