Changes in Perampanel Pharmacokinetics and Cytochrome P450 3A4 Activity Before, During, and After Pregnancy.

ABSTRACT: This study evaluated perampanel pharmacokinetics and cytochrome P450 3A4 (CYP3A4) activity, assessed using the level of 4ß-hydroxycholesterol (4ß-OHC) as an endogenous biomarker of CYP3A4, before, during, and after pregnancy in a woman with epilepsy and compared these measurements with those from a control group of nonpregnant women with epilepsy. A 21-year-old pregnant woman was being treated with perampanel (serum concentration: 1120 ng/mL), lacosamide, and lamotrigine. After the first trimester, the lamotrigine concentration decreased markedly; however, the perampanel concentration remained almost unchanged (range, 1130-1320 ng/mL). Similarly, serum 4ß-OHC levels did not change during pregnancy (before pregnancy, 78.2 ng/mL; during pregnancy, 62.2-83.2 ng/mL). To compare these measurements with those in nonpregnant women, we enrolled 27 nonpregnant women with epilepsy (age range, 16-40 years). In the control patients, we found a strong negative correlation between the concentration-to-dose ratio of perampanel and the 4ß-OHC level ( r = -0.78, P < 0.001). As there was no significant change in CYP3A4 activity, we concluded that the serum perampanel concentration did not change significantly before, during, or after pregnancy. More patients need to be studied to confirm these early results.

Neuropsychological outcome after frontal surgery for pediatric-onset epilepsy with focal cortical dysplasia in adolescent and young adult.

OBJECTIVE: We investigated neuropsychological outcome in patients with pharmacoresistant pediatric-onset epilepsy caused by focal cortical dysplasia (FCD), who underwent frontal lobe resection during adolescence and young adulthood. METHODS: Twenty-seven patients were studied, comprising 15 patients who underwent language-dominant side resection (LDR) and 12 patients who had languagenondominant side resection (n-LDR). We evaluated intelligence (language function, arithmetic ability, working memory, processing speed, visuo-spatial reasoning), executive function, and memory in these patients before and two years after resection surgery. We analyzed the relationship between neuropsychological outcome and resected regions (side of language dominance and location). RESULTS: Although 75% of the patients showed improvement or no change in individual neuropsychological tests after surgical intervention, 25% showed decline. The cognitive tests that showed improvement or decline varied between LDR and n-LDR. In patients who had LDR, decline was observed in Vocabulary and Phonemic Fluency (both 5/15 patients), especially after resection of ventrolateral frontal cortex, and improvement was observed in WCST-Category (7/14 patients), Block Design (6/15 patients), Digit Symbol (4/15 patients), and Delayed Recall (3/9 patients). In patients who underwent n-LDR, improvement was observed in Vocabulary (3/12 patients), but decline was observed in Block Design (2/9 patients), and WCST-Category (2/9 patients) after resection of dorsolateral frontal cortex; and Arithmetic (3/10 patients) declined after resection of dorsolateral frontal cortex or ventrolateral frontal cortex. General Memory (3/8 patients), Visual Memory (3/8 patients), Delayed Recall (3/8 patients), Verbal Memory (2/9 patients), and Digit Symbol (3/12 patients) also declined after n-LDR. CONCLUSION: Postoperative changes in cognitive function varied depending on the location and side of the resection. For precise presurgical prediction of neuropsychological outcome after surgery, further prospective studies are needed to accumulate data of cognitive changes in relation to the resection site.

Time-Course Changes in Lamotrigine Concentration after Addition of Valproate and the Safety and Long-Term Tolerability of Lamotrigine-Valproate Combination Therapy.

The aim of this study was to evaluate the time-course changes in lamotrigine (LTG) concentration after addition of valproate (VPA) and the safety and tolerability of the combination therapy. We reviewed our therapeutic drug monitoring (TDM) database and found 345 patients on LTG who received add-on therapy with VPA. VPA had been added at least 12 weeks after patients finished stepwise LTG titration. Also, we retrospectively evaluated the LTG concentration after addition of VPA and the safety and long-term tolerability of LTG-VPA combination therapy. Plasma LTG concentration increased more than 1.5-fold within 15 d of addition of VPA and reached a peak at 30 d. The rate of increase in LTG concentration occurred in a VPA concentration-dependent manner. During the first 120 d after addition of VPA, adverse events were reported by 58 patients (16.8%), but no patient developed cutaneous reactions. Kaplan-Meier analysis showed estimated retention rates for LTG-VPA combination therapy of 74.5% at 5 years. At 5 years, the mean concentration of LTG was 11.1 µg/mL (43.3 µmol/L). Because addition of VPA leads to a marked increase in LTG concentration over a short period, TDM for LTG should be performed at the earliest from 14 d after starting VPA. At 120 d after starting VPA therapy, the higher LTG concentration due to addition of VPA is not associated with an increased risk of cutaneous reactions. Although LTG-VPA combination therapy increases LTG concentration, it is well tolerated and has a high long-term retention rate.

Effects of low-dose titration on the tolerability and safety of perampanel.

PURPOSE: To evaluate the effects of low-dose titration on the tolerability and safety of perampanel. METHODS: We retrospectively reviewed the records of 1065 patients who started perampanel therapy and compared the incidence of adverse events after standard titration (Group A: starting dose, 2 mg/day; titration speed, 2 mg/2 weeks or longer) and low-dose titration (Group B: starting dose, < 1 mg/day; titration speed, < 1 mg/2 weeks or longer). RESULTS: Adverse events were reported in 158 patients (14.8%) within the initial first 90 days of starting perampanel (mean concentration, 331 ng/mL). At 90 days, the cumulative incidence of adverse events was significantly higher in Group A than in Group B (24.5% vs. 16.3%, respectively; log-rank test p < 0.001). A Cox proportional hazards model also showed that low-dose titration decreased the incidence risk of adverse events (adjusted hazard ratio, 0.49; 95% confidence interval, 0.35-0.69). When the groups were stratified by use of enzyme-inducing antiseizure medications (inducers), Group A patients without inducers had a significantly higher cumulative incidence of adverse events than the other three subgroups (26.7%, p < 0.001). In patients taking 2 mg of perampanel, median concentrations in patients with or without inducers were 43 ng/mL and 204 ng/mL, respectively. CONCLUSION: Perampanel is generally initiated at 2 mg, but serum perampanel concentrations show substantial interindividual variation. Our study suggests that care must be taken when setting the starting dose of perampanel. In particular, low-dose titration is recommended in patients not taking inducers.

Therapeutic Drug Monitoring for Rufinamide in Japanese Patients With Epilepsy: Focus on Drug Interactions, Tolerability, and Clinical Effectiveness.

BACKGROUND: The purposes of this study were to assess drug interactions between rufinamide and concomitant antiepileptic drugs (AEDs) and to identify the therapeutic window for rufinamide. METHODS: Serum samples (n = 1531) were obtained from 178 patients (aged 2-57 years), and clinical records were retrospectively reviewed to evaluate the safety and efficacy of rufinamide (mean observation time, 1073 ± 846 days). RESULTS: Rufinamide exhibited linear pharmacokinetics at doses of up to 60 mg/kg (range, 50-3200 mg/d). Concomitant use of the enzyme-inducing AEDs such as phenytoin, carbamazepine, and phenobarbital reduced rufinamide concentrations by 43.4%, 13.2%, and 30.3%, respectively. By contrast, concomitant use of valproate significantly elevated rufinamide concentrations. Clinical response was seen in 41 patients (23.0%), with a median therapeutic concentration (interquartile range) of 20.6 mcg/mL (13.3-27.0). There was no difference in the therapeutic concentrations between seizure types, but patients with tonic/atonic seizures tended to have higher rufinamide concentrations. During the study period, adverse events were reported in 64 patients (35.8%), including somnolence, gastrointestinal disorders, dizziness, and irritability/behavior disorders. Conditional logistic regression analysis showed that patients administered a concentration greater than 20 mcg/mL had an 8.6-fold higher incidence of adverse events. CONCLUSIONS: Therapeutic drug monitoring for rufinamide is clinically useful for predicting drug interactions between rufinamide and concomitant AEDs. When a patient has tonic/atonic seizures, careful titration is required for concentrations greater than 20 mcg/mL.

Risk factors for psychiatric adverse effects associated with perampanel therapy.

PURPOSE: To identify the risk factors for psychiatric adverse effects associated with perampanel therapy. METHODS: We retrospectively evaluated the adverse effects of perampanel by reviewing clinical records from 895 Japanese patients with epilepsy (aged 1-86 years) who started perampanel therapy at National Epilepsy Center, Shizuoka, Japan, between June 2016 and December 2019. Patients were classified into 3 groups: those without adverse effects (Group I), those with psychiatric adverse effects (Group II), and those with common adverse effects (Group III). RESULTS: The number of patients assigned to each group was as follows: Group I, n = 641; Group II, n = 93; and Group III, n = 161. The mean follow-up period was 458 ±â€¯265 days (median, 511 days). Kaplan-Meier survival estimates showed that the median time to treatment failure was shorter in Group II than in Group III (294 vs. 392 days, respectively; log-rank test, p < 0.001). According to polytomous logistic regression, younger age (<16 years) was associated with a lower risk of common and psychiatric adverse effects. The risk factors for psychiatric adverse effects (Group II) were intellectual disability (adjusted odds ratio [AOR], 2.6; 95% confidence interval (CI), 1.5-4.5) and psychiatric comorbidity (AOR, 3.8; 95% CI, 2.3-6.3); in patients with intellectual disability, the occurrence of psychiatric adverse effects was concentration dependent. Patients with lamotrigine use had a 0.54-fold lower risk of psychiatric adverse effects. In Group III, concomitant use of inducers was associated with a decreased risk of common adverse effects (AOR, 0.68; 95% CI, 0.46-0.99). SIGNIFICANCE: We found clear differences in the risk factors for psychiatric adverse effects. In patients with intellectual disability, care must be taken when titrating perampanel, and therapeutic drug monitoring should be performed.

Identification of new biomarkers of pyridoxine-dependent epilepsy by GC/MS-based urine metabolomics.

α-Aminoadipic semialdehyde and its cyclic form (Δ1-piperideine-6-carboxylate) accumulate in patients with α-aminoadipic semialdehyde dehydrogenase (AASADH; antiquitin; ALDH7A1) deficiency. Δ1-Piperideine-6-carboxylate is known to react with pyridoxal 5'-phosphate (PLP) to form a Knoevenagel condensation product, resulting in pyridoxine-dependent epilepsy. Despite dramatic clinical improvement following pyridoxine supplementation, many patients still suffer some degree of intellectual disability due to delayed diagnosis. In order to expedite the diagnosis of patients with suspected AASADH deficiency and minimize the delay in treatment, we used gas chromatography-mass spectrometry-based metabolomics to search for potentially diagnostic biomarkers in urine from four patients with ALDH7A1 mutations, and identified Δ2-piperideine-6-carboxylate, 6-oxopipecolate, and pipecolate as candidate biomarkers. In a patient at postnatal day six, but before pyridoxine treatment, Δ2-piperideine-6-carboxylate and pipecolate were present at very high concentrations, indicating that these compounds may be good biomarkers for untreated AASADH deficiency patients. On the other hand, following pyridoxine/PLP treatment, 6-oxopipecolate was shown to be greatly elevated. We suggest that noninvasive urine metabolomics screening for Δ2-piperideine-6-carboxylate, 6-oxopipecolate, and pipecolate will be useful for prompt and reliable diagnosis of AASADH deficiency in patients within any age group. The most appropriate combination among Δ2-piperideine-6-carboxylate, 6-oxopipecolate, and pipecolate as biomarkers for AASADH deficiency patients appears to depend on the age of the patient and whether pyridoxine/PLP supplementation has been implemented. We anticipate that the present bioanalytical information will also be useful to researchers studying glutamate, proline, lysine and ornithine metabolism in mammals and other organisms.

Impact of CYP2C19 Phenotypes on Clinical Efficacy of Stiripentol in Japanese Patients With Dravet Syndrome.

BACKGROUND: Stiripentol is a strong inhibitor of CYP2C19 and CYP3A4. This study compared the effect of stiripentol on the pharmacokinetics of clobazam and N-desmethyl-clobazam (NCLB; an active metabolite of clobazam) between different CYP2C19 phenotypes. We also evaluated the clinical impact of CYP2C19 phenotypes in Japanese patients with Dravet syndrome receiving a combination of valproic acid, clobazam, and stiripentol. METHODS: We retrospectively reviewed 241 blood samples from 64 patients (aged 1-40 years) and calculated the concentration/dose (CD) ratio [serum level (ng/mL) divided by dose (mg/kg)] for clobazam and NCLB. Based on their CYP2C19 genotypes, patients were classified as extensive metabolizers (EM group: CYP2C19*1/*1, *1/*2, or *1/*3) or poor metabolizers (PM group: CYP2C19*2/*2, *3/*3, or *2/*3). We also reviewed the clinical records of 56 patients who commenced stiripentol therapy and calculated the retention rate for stiripentol therapy over an observation period of 208 weeks. RESULTS: Concomitant administration of stiripentol led to a marked increase in the CD ratio of clobazam (1.8-fold in the EM group and 1.5-fold in the PM group). In addition, stiripentol increased the CD ratio of NCLB by 6.6-fold in the EM group, but decreased it by 0.7-fold in the PM group. The estimated retention rate with stiripentol therapy was higher, and the duration of retention was longer in the EM group than in the PM group (1378 versus 933 days, P < 0.001). In patients with the PM phenotype, the adjusted hazard ratio for ceasing stiripentol therapy was 6.7 (95% confidence interval: 1.8-24.7, P < 0.005). CONCLUSIONS: The effect of stiripentol on the pharmacokinetics of NCLB was significantly different between patients with the EM and PM phenotypes, which could influence the clinical response of Japanese patients with Dravet syndrome receiving the combination of valproic acid, clobazam, and stiripentol.

Therapeutic Monitoring of Lacosamide in Japanese Patients With Epilepsy: Clinical Response, Tolerability, and Optimal Therapeutic Range.

BACKGROUND: Lacosamide is a novel anticonvulsant that acts by enhancing sodium channel slow inactivation. The aims of this study were to evaluate the influence of concomitant antiepileptic drugs (AEDs) on serum lacosamide concentration and explore the relationship between lacosamide serum concentration and both clinical response and adverse effects. METHODS: The authors analyzed 649 serum samples from 426 Japanese patients with epilepsy. The concentration-to-dose (CD) ratio of lacosamide was compared among patients on various AED regimens. Clinical information about seizure frequency and adverse events was obtained from clinical records. RESULTS: In patients who did not receive enzyme-inducing AEDs, the CD ratio (mean ± SD) of lacosamide was 1.84 ± 0.68. By contrast, the CD ratio in patients who received phenytoin, carbamazepine, and phenobarbital was 1.42 ± 0.66 (22.8% lower), 1.46 ± 0.40 (20.7% lower), and 1.36 ± 0.38 (26.1% lower), respectively. Seventy-four patients (17.3%) achieved >50% seizure reduction. The median lacosamide concentration in patients who received and did not receive a sodium channel blocker was 6.6 mcg/mL (26.4 µmol/L) and 8.4 mcg/mL (33.6 µmol/L), respectively. Adverse events, including dizziness, somnolence, diplopia, and anorexia, were reported by 70 patients (16.4%). The incidence rate in patients treated with sodium channel blockers was significantly higher than that in patients not treated with these drugs (21.1% vs. 10.3%; P < 0.005), and the median lacosamide concentration in these patient groups was 5.1 (20.4 µmol/L) and 7.5 mcg/mL (30 µmol/L), respectively. CONCLUSIONS: Therapeutic drug monitoring of lacosamide is clinically useful because it allows physicians to estimate the extent of drug interactions and adjust the dose in individual AED regimens.

Methylprednisolone pulse therapy in 31 patients with refractory epilepsy: A single-center retrospective analysis.

PURPOSE: We investigated the efficacy of methylprednisolone pulse therapy (MP) and responder characteristics in patients with refractory epilepsy. METHODS: We reviewed medical records of our center to identify patients with refractory epilepsy treated with MP other than continuous spikes and waves during slow sleep (CSWS), Landau-Kleffner syndrome (LKS), or Rasmussen's syndrome (RS) between 2004 and 2015. A course of MP consisted of intravenous methylprednisolone (30 mg/kg/day) on three consecutive days. Patients received multiple courses at intervals of four weeks. We examined seizure outcome, developmental outcome, antibodies to N-methyl-d-aspartate (NMDA)-type glutamate receptors (GluRs), cerebral spinal fluid (CSF)-albumin/serum-albumin ratio, and interictal electroencephalograms (EEGs). Responder to MP was defined as maintaining seizure reduction rate (SRR) ≥50% for three months after the first course of MP. RESULTS: Thirty-one consecutive patients treated with MP at our center were studied. Seizure types were focal onset impaired awareness seizure (FIAS) only (n = 23), FIAS with epileptic spasms (ES) (n = 7), and ES only (n = 1). Responder rate was 32.2% (10/31 patients), and seizure-free rate was 9.7% (3/31). Responders constituted 43.5% of patients without ES. No patient with ES was responder. Behavior and cognition also improved in 6 of 10 responders. History of seizure aggravation after inactivated vaccine before MP was found significantly higher rate in responder patients, comparing with nonresponder patients (p = 0.01). CONCLUSION: Methylprednisolone pulse therapy may be considered for possible treatment in patients with focal epilepsy with drug-resistant seizures without ES, and it may improve cognitive function and behavioral comorbidities.

Influence of Inflammation on the Pharmacokinetics of Perampanel.

BACKGROUND: It is well-known that the pharmacokinetics of various drugs are influenced by inflammation. This study evaluated the relationship between C-reactive protein (CRP; an inflammation marker) and the pharmacokinetics of perampanel. METHODS: Among 111 patients who underwent measurement of both CRP and perampanel, 23 patients had a serum CRP level exceeding 1.5 mg/dL (CRP-positive). We compared the concentration/dose ratio (CD ratio) of perampanel in these 23 patients between the times when they were CRP-positive and CRP-negative. To evaluate the effect of CRP on the CD ratio, multiple regression analysis was performed with the following covariates: CRP-positive status, body weight, and use of phenytoin, carbamazepine, or phenobarbital, and combinations of these drugs. RESULTS: In 10 patients using enzyme-inducing antiepileptic drugs (AEDs), the mean CD ratio increased by 53.5% [from 1389 to 2132 (ng/mL)/(mg/kg)] when they were CRP-positive. In 13 patients without enzyme-inducing AEDs, the mean CD ratio increased by 100.8% [from 3826 ng/mL to 7683 (ng/mL)/(mg/kg)] when they were CRP-positive. By multiple regression analysis, the CRP level was a significant independent determinant of the CD ratio of perampanel. Despite a marked increase of the CD ratio, no adverse events were reported. CONCLUSIONS: Irrespective of concomitant administration of enzyme-inducing AEDs, the serum perampanel concentration showed a marked increase in patients with inflammation. However, this increase was not associated with central nervous system toxicity. Although it is unknown whether the concentration of free and/or bound perampanel was increased, it seems likely that dose reduction is unnecessary for elevation of the serum perampanel level in patients with inflammation.

Influence of Renal Function on Pharmacokinetics of Antiepileptic Drugs Metabolized by CYP3A4 in a Patient With Renal Impairment.

BACKGROUND: Several studies have demonstrated that renal impairment not only decreases renal clearance but also hepatic clearance of medications that are CYP3A4 substrates. We evaluated the influence of renal function on the pharmacokinetics of antiepileptic drugs metabolized by CYP3A4. METHODS: We retrospectively calculated the concentration/dose ratio (CD ratio) for topiramate and clobazam in an epilepsy patient with renal impairment. In addition, we determined the CD ratio of perampanel in 17 patients with normal renal function and compared it with that in the patient with renal impairment. RESULTS: A patient with frontal lobe epilepsy and mild renal impairment [creatinine clearance (CCr): 67.7 mL/min] was taking phenytoin and 3 CYP3A4 substrates (topiramate, clobazam, and perampanel). With progression of renal impairment (CCr: 28.1 mL/min), the CD ratios of topiramate and clobazam increased by about 2-fold. The mean CD ratio of perampanel was 1740 ± 966 ng·mL·mg·kg in the 17 patients with normal renal function using phenytoin. By contrast, the CD ratio of perampanel was markedly higher (range: 5327-9113 ng·mL·mg·kg) in the patient with renal impairment (CCr: <20 mL/min). CONCLUSIONS: These findings suggest that dose adjustment based on therapeutic drug monitoring is probably necessary when topiramate, clobazam, or perampanel is prescribed for patients with moderate-to-severe renal impairment.

Effect of CYP Inducers/Inhibitors on Topiramate Concentration: Clinical Value of Therapeutic Drug Monitoring.

BACKGROUND: This study investigated the pharmacokinetic interactions between topiramate (TPM) and concomitant antiepileptic drugs and evaluated the therapeutic concentration range of TPM and the effect of the achieved plasma concentration on the retention rate of TPM therapy. METHODS: A total of 1217 plasma samples obtained from 610 patients were retrospectively investigated, and the concentration-to-dose ratio (CD ratio) of TPM was compared among patients on various antiepileptic drug regimens. In addition, the therapeutic concentration of TPM was reviewed in patients on long-term therapy, and factors influencing the retention rate of TPM were analyzed by the Kaplan-Meier method. RESULTS: Among patients using hepatic enzyme inducers (phenytoin, phenobarbital, and carbamazepine), the CD ratio was reduced by 45.4% in adults and 33.3% in children. Patients taking phenytoin concomitantly had a significantly lower CD ratio than patients taking phenobarbital or carbamazepine. Among noninducers, concomitant use of stiripentol increased the CD ratio. In 276 patients who remained on TPM therapy for more than 2 years, the mean therapeutic concentration was 5.1 mcg/mL (15.0 µmol/L). The estimated retention day was significantly higher for patients with a TPM concentration >5 mcg/mL than that for patients with a concentration <5 mcg/mL (945 versus 802 days; P = 0.007 by the log-rank test). Also, patients without hepatic enzyme inducers had a significantly higher retention rate than patients using such inducers (P = 0.002). CONCLUSIONS: Concomitant use of hepatic enzyme inducers markedly reduced the plasma TPM concentration and can decrease its antiepileptic effect. A therapeutic concentration of >5 mcg/mL TPM was significantly associated with continuation of therapy, and therapeutic drug monitoring can be helpful.

Therapeutic Drug Monitoring for Perampanel in Japanese Epilepsy Patients: Influence of Concomitant Antiepileptic Drugs.

BACKGROUND: Perampanel is a new antiepileptic drug (AED) that acts as a noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor antagonist and is mainly metabolized by cytochrome P450 (CYP) 3A4. This study evaluated the influence of concomitant AEDs on the serum concentration profile of perampanel. METHODS: A total of 215 serum samples obtained from 76 patients aged 12 years or older were analyzed for routine therapeutic drug monitoring, and the concentration-to-dose ratio (CD ratio) of perampanel was compared among patients on various AED regimens. RESULTS: In patients not taking concomitant enzyme-inducing AEDs, the mean CD ratio was 3963 ng·mL·mg·kg (range: 1793-13,299). By contrast, the mean CD ratio was lower in patients using enzyme-inducing AEDs [1760 (range: 892-3090), 2256 (range: 700-4703), and 1120 (range: 473-1853) ng·mL·mg·kg in patients taking phenytoin, phenobarbital, and carbamazepine, respectively], and carbamazepine had a significantly greater reduction in the CD ratio compared with phenytoin or phenobarbital (P < 0.001). Twenty-one patients responded with ≥50% reduction of seizure frequency from baseline, and their mean serum perampanel concentration was 450 ng/mL (range: 85-1500). CONCLUSIONS: There is a large interindividual variation in CD ratio of perampanel because its metabolism is highly susceptible to interactions with enzyme-inducing AEDs. Therapeutic drug monitoring could be clinically useful for determining the influence of AED CYP3A4 inducers on perampanel concentrations.

A case of CDKL5 disorder: improved ADL by simple treatment strategy for intractable epileptic seizures.

CDKL5 gene mutations are the cause of symptomatic infantile epilepsy in some patients. Such patients present with partial seizures and characteristic hand movements that are often observed in patients with Rett syndrome. This clinical entity has recently been recognized as CDKL5 disorder. In a girl with CDKL5 disorder, who had been treated with combinatory therapy using many anti-epileptic drugs, we were able to control the seizures with valproate monotherapy. As a result of the monotherapy, the patient's seizures ameliorated temporarily and her quality of life improved. Some patients show improvement in seizures during the natural course of CDKL5 disorder. Therefore, there is a possibility that this was also the case in our patient. However, the patient and her family were satisfied with the improvement in quality of life after the withdrawal of the multi-drug combinatory therapy. Thus, it is important to select the best therapy for patients with intractable epilepsy through long term follow-up.

Factors that influence the pharmacokinetics of lamotrigine in Japanese patients with epilepsy.

PURPOSE: Lamotrigine (LTG) is used to treat epilepsy. The variability of LTG pharmacokinetics among individuals may be attributed to polymorphisms in the genes of uridine diphosphate glucuronosyltransferases (UGTs) 1A4 and UGT2B7 and/or combination with other drugs. In this study, we evaluated the association between LTG concentrations and patient characteristics such as genetic polymorphisms and the co-administration of antiepileptic drugs. METHODS: We recruited 122 patients with epilepsy. LTG concentrations were measured in blood samples from each patient under steady-state condition. We assessed the influence of multiple factors on LTG concentrations and derived a formula for predicting LTG concentrations using multiple linear regression analysis. RESULTS: We derived a formula to predict LTG concentrations that considers the daily dose of LTG, body weight, valproic acid concentration, phenytoin co-administration, and the co-administration of phenobarbital and/or carbamazepine as well as UGT1A4 142T>G and UGT2B7 -161C>T polymorphisms (adjusted coefficients of determination R (2) = 0.734). Furthermore, we used this formula to reveal a strong positive correlation between measured and predicted LTG concentrations (r (2) = 0.76, p < 0.001). CONCLUSION: We derived a formula that will be useful in clinical practice for predicting LTG concentrations in patients with epilepsy.

Individualized phenytoin therapy for Japanese pediatric patients with epilepsy based on CYP2C9 and CYP2C19 genotypes.

BACKGROUND: The aims of this study were to identify the target dose of phenytoin (PHT) and to compare the treatment continuation rate between patients receiving conventional therapy and patients receiving individualized therapy based on genotyping of the CYP2C9*3, CYP2C19*2, and CYP2C19*3 alleles. The operational definition for the target dose of PHT used in this study was the dose that yielded a steady-state PHT concentration within the range of 15-20 mcg/mL without dose-related adverse effects. METHODS: We investigated 394 samples from 170 Japanese pediatric patients aged 9 months to 15 years to identify factors that influenced the target dose of PHT. We also analyzed the clinical records of 156 patients who commenced PHT therapy at our hospital and retrospectively assessed the time to treatment failure within 1 year after starting PHT therapy. During the study period, 17 patients underwent genotyping at the start of PHT therapy. If the patients had the CYP2C9*3, CYP2C19*2, or CYP2C19*3 alleles, the initial dose of PHT was reduced by 10%-50% according to previous reports. The other 139 patients received conventional PHT therapy. RESULTS: According to multiple regression analysis, the body weight, concomitant use of sulthiame, and the CYP2C9*3, CYP2C19*2, and CYP2C19*3 alleles influenced the target dose of PHT. Our model explained 74% of the interindividual variability of the target dose of PHT. The total withdrawal rate in the individualized therapy group and the conventional therapy group was 23.5% and 33.1%, respectively. The adjusted hazard ratio for withdrawal of PHT therapy in the individualized therapy group was 0.37 (95% confidence interval; 0.12-1.10, P = 0.074). CONCLUSIONS: These findings suggest that genotyping can help to estimate the optimum target dose of PHT and may contribute to avoid intoxication and concentration-dependent adverse effects.

Changing incidence of hyperammonemia in Japan from 2006 to 2013: expansion of new antiepileptic drugs reduces the risk of hyperammonemia.

PURPOSE: The purpose of the present study was to examine the relationship between the incidence of hyperammonemia and changes in the prescribing of concomitant antiepileptic drugs (AEDs) in patients receiving valproic acid. METHODS: We evaluated 40,363 plasma samples from 6009 epilepsy patients obtained from 2006 to 2013. Hyperammonemia was defined as a plasma ammonia level exceeding 100 µg/dL. RESULTS: In 2006, 32.6 % of the plasma samples were from patients with concomitant use of phenytoin but this decreased to 16.0 % in 2013. Lamotrigine and levetiracetam were approved in 2008 and 2010, respectively, and were prescribed for patients who provided 27.8 and 14.9 % of the plasma samples in 2013. The incidence rate of hyperammonemia (per 100 person years) decreased markedly from 40.8 (95 % confidence interval (CI), 37.7-43.9) in 2006 to 14.2 (95 % CI, 12.5-15.9) in 2013. In any year reviewed, concomitant use of phenytoin, phenobarbital, carbamazepine, or carbonic anhydrase inhibitors was a risk factor for hyperammonemia. Among enzyme-inducing AEDs, concomitant use of phenytoin was associated with the highest risk of hyperammonemia. CONCLUSION: Drug interactions caused by enzyme-inducing AEDs, especially phenytoin, are closely related to the development of hyperammonemia. This study demonstrated that introduction of new AEDs changed the co-prescribing pattern in patients receiving valproic acid, resulting in a marked decrease of hyperammonemia. Although their higher cost may be problematic, new AEDs are beneficial for reducing the risk of drug interactions.

Long-term course of Dravet syndrome: a study from an epilepsy center in Japan.

OBJECTIVE: This study attempted to clarify the long-term course of Dravet syndrome (DS). METHODS: Sixty-four patients diagnosed with DS (44 with typical DS, and 20 with atypical DS) were studied. The long-term outcomes of clinical seizures, electroencephalographic findings, neuropsychological findings, and social situation were analyzed. The follow-up period ranged from 11 to 34 years 5 months (median 24 years). RESULTS: At the last visit, the ages ranged from 19 years to 45 years (median 30 years). Fifty-nine patients continued to have generalized tonic-clonic seizures (GTCS). Status epilepticus and unilateral seizures were not observed and myoclonic seizures, atypical absence seizures, and photosensitive seizures were resolved in most patients. The frequency of complex partial seizures was equally low, with five patients at presentation and six patients at the last visit, respectively. Five patients achieved seizure remission (seizure-free for 1 year or longer). Only 1 of 44 patients with typical DS had seizure remission, whereas 4 of 20 patients with atypical DS remitted, with a statistically significant difference between the two phenotypes (p = 0.03). Intellectual disability was found in all patients; especially, severe intellectual disability was prevalent. Patients with atypical DS tended to have milder intellectual disability compared to those with typical DS (p = 0.0283). Occipital alpha rhythm in the basic activity was associated with milder intellectual disability (p = 0.0085). The freedom from seizures correlated with appearance of occipital alpha rhythms (p = 0.0008) and disappearance of epileptic discharges (p = 0.0004). Two patients with GTCS died. Mutations of the neuronal voltage-gated sodium channel alpha subunit type 1 gene were detected at a high frequency (33 of 36 patients examined). Seizure remission was found only in the missense mutation group. SIGNIFICANCE: The long-term seizure and intellectual outcomes are extremely poor in patients with typical DS compared to those with atypical DS. Epilepsy phenotype may influence long-term course of DS.