topiramate and eslicarbazepine-acetate

The safety of switching between generic products of antiseizure medications (ASMs) continues to be a hot topic in epilepsy management. The main reason for concern relates to the uncertainty on whether, and when, two generics found to be bioequivalent to the same brand (reference) product are bioequivalent to each other, and the risk of a switch between generics resulting in clinically significant changes in plasma ASM concentrations. This article addresses these concerns by discussing the distinction between bioequivalence and statistical testing for significant difference, the importance of intra-subject variability in interpreting bioequivalence studies, the stricter regulatory bioequivalence requirements applicable to narrow-therapeutic-index (NTI) drugs, and the extent by which currently available generic products of ASMs comply with such criteria. Data for 117 oral generic products of second-generation ASMs approved in Europe by the centralized, mutual recognition or decentralized procedure were analyzed based on a review of publicly accessible regulatory assessment reports. The analysis showed that for 99% of generic products assessed (after exclusion of gabapentin products), the 90% confidence intervals (90% CIs) of geometric mean ratios (test/reference) for AUC (area under the drug concentration vs time curve) were narrow and wholly contained within the acceptance interval (90%-111%) applied to NTI drugs. Intra-subject variability for AUC was <10% for 53 (88%) of the 60 products for which this measure was reported. Many gabapentin generics showed broader, 90% CIs for bioequivalence estimates, and greater intra-subject variability, compared with generics of other ASMs. When interpreted within the context of other available data, these results suggest that any risk of non-bioequivalence between these individual generic products is small, and that switches across these products are not likely to result in clinically relevant changes in plasma drug exposure. The potential for variability in exposure when switching across generics is likely to be greatest for gabapentin.

Topics: Anticonvulsants; Area Under Curve; Biological Variation, Individual; Dibenzazepines; Drug Substitution; Drugs, Generic; Europe; Gabapentin; Humans; Lacosamide; Lamotrigine; Levetiracetam; Oxcarbazepine; Pregabalin; Therapeutic Equivalency; Topiramate; Vigabatrin; Zonisamide

This study was proposed to compare the relative efficacy and tolerability of the second and third generation AEDs for refractory epilepsy. The 50% responder rate (RR) was selected as the efficacy outcome whereas the incidence of dizziness and somnolence were considered to evaluate the tolerability of AEDs. Odds ratio (OR) and their 95% credible interval (CrI) were obtained using a consistency model and surface under the cumulative ranking curve (SUCRA) value was calculated to rank AEDs. Topiramate appeared to be significantly more effective than placebo, eslicarbazepine acetate, perampanel, pregabalin, zonisamide, gabapentin and lamotrigine with respect to the 50% RR (all OR > 1). Patients who were managed by eslicarbazepine acetate, perampanel, oxcarbazepine, topiramate and pregabalin were more likely to suffer from dizziness compared to those who receive placebo (all OR > 1). Perampanel, topiramate and pregabalin were related to elevated risks of somnolence compared to placebo (all OR > 1). Moreover, topiramate ranked highest with respect to 50% RR (SUCRA = 0.968) whereas levetiracetam appeared to have balanced efficacy and tolerability (SUCRA = 0.769, 0.743, 0.604 and 0.659). In conclusion, topiramate was the most efficacious AED, while levetiracetam was able to provide patients with balanced efficacy and tolerability.

Topics: Anticonvulsants; Dibenzazepines; Drug Resistant Epilepsy; Humans; Levetiracetam; Network Meta-Analysis; Nitriles; Pyridones; Topiramate

Combination therapy is frequently required in the management of epilepsy. The primary objective of this study was to investigate the pharmacokinetic interaction between eslicarbazepine acetate (ESL) 1200 mg once daily and topiramate (TPM) 200 mg once daily in healthy subjects.. Multiple-dose, open-label, one-sequence study in two parallel groups of 16 healthy male volunteers. After an 8-day treatment with ESL (Group A) or TPM (Group B), ESL and TPM were co-administered for 19 days. A bioequivalence approach based on a within-subject comparison was used to investigate a potential drug-drug interaction. End/start of treatment geometric mean ratios (GMR, %) and 90% confidence intervals (90% CI) were calculated for maximum plasma concentration (C(max)) and area under the plasma concentration-time curve over the dosing interval at steady-state (AUC(ss)) of eslicarbazepine (ESL major active metabolite), R-licarbazepine (ESL minor active metabolite) and TPM at Day 8 and Day 27.. In Group A, eslicarbazepine GMR (90% CI) was 86.79% (81.06%; 92.94%) for C(max) and 92.70% (89.21%; 96.32%) for AUC(ss). In Group B, TPM GMR (90% CI) was 81.50% (77.48%; 85.89%) for C(max) and 81.81% (79.69%; 84.00%) for AUC(ss). The 90% CI of eslicarbazepine C(max) and AUC(ss) fell within the pre-specified bioequivalence range (80.00%; 125.00%), allowing it to be concluded that the extent of systemic exposure to eslicarbazepine was unaffected by the concomitant administration of TPM. The 90% CI for topiramate AUC(ss) was borderline in relation to the pre-specified bioequivalence range and topiramate C(max) fell outside the pre-specified bioequivalence range. Therefore, the extent of systemic exposure to TPM following co-administration with ESL was not formally bioequivalent to the extent of systemic exposure to TPM when TPM was administered alone. However, there was no difference between TPM elimination half-life following TPM co-administered with ESL and TPM administered alone (24.0 and 24.3 h, respectively). The bioavailability of R-licarbazepine was essentially bioequivalent. Two subjects discontinued due to adverse events. No clinical interaction appeared to be present in terms of adverse events when both drugs were given concomitantly.. Concomitant administration of eslicarbazepine acetate 1200 mg once daily and topiramate 200 mg once daily showed no significant change in exposure to eslicarbazepine but an 18% decrease in exposure to topiramate, most likely caused by a reduced bioavailability of topiramate. No dose adjustment is required.

Topics: Adult; Anticonvulsants; Dibenzazepines; Drug Interactions; Fructose; Humans; Male; Middle Aged; Quebec; Topiramate; Young Adult

Psychiatric comorbidities are common in people with epilepsy. A retrospective study of characteristics associated with withdrawal due to psychiatric side effects was undertaken in patients with treated epilepsy participating in prospective audits with new antiepileptic drugs (AEDs). A total of 1058 treated patients with uncontrolled seizures (942 focal-onset seizures, 116 generalized genetic epilepsies [GGEs]) participated in eight prospective, observational audits from 1996 to 2014. These patients were prescribed adjunctive topiramate (n=170), levetiracetam (n=220), pregabalin (n=135), zonisamide (n=203), lacosamide (n=160), eslicarbazepine acetate (n=52), retigabine (n=64), or perampanel (n=54). Doses were titrated according to efficacy and tolerability to optimize zeizure outcomes and reduce side effects. Psychiatric comorbidities were recorded prior to and after the addition of each AED. At baseline, patients with focal-onset seizures (189 of 942; 20.1%) were statistically more likely to have psychiatric diagnoses compared to patients with GGEs (14 of 116, 12.1%; p=0.039). Following adjunctive AED treatment, neuropsychiatric adverse effects led to AED withdrawal in 1.9-16.7% of patients. Patients with a pre-treatment psychiatric history (22 of 209; 10.5%) were statistically more likely to discontinue their new AED due to psychiatric issues compared to patients with no previous psychiatric diagnosis (50 of 849; 5.9%; p=0.017). Patients receiving sodium channel blocking AEDs (4 of 212, 1.9%) were statistically less likely to develop intolerable psychiatric problems, compared to those on AEDs possessing other mechanisms of action (68 of 846, 8.0%; p=0.012). Depression was the commonest problem, leading to discontinuation of AEDs in 2.8% (n=30) patients. Aggression was statistically more common in men (11 of 527, 2.1%) compared to women (1 of 531, 0.2%; p=0.004). Patients with learning disability (12 of 122, 9.8%; p=0.0015) were statistically less likely to have psychiatric issues prior to adjunctive AED treatment compared to other patients (208 of 936, 22.2%), but there were no statistically significant differences once the new AEDs were added (8 of 122 patients with learning disability, 6.6%; 64 of 936 other patients, 6.8%). Awareness of these issues may assist clinicians in avoiding, identifying and treating psychiatric comorbidities in people with epilepsy.

Topics: Acetamides; Adolescent; Adult; Aged; Aged, 80 and over; Anticonvulsants; Dibenzazepines; Drug-Related Side Effects and Adverse Reactions; Epilepsy; Female; Fructose; Humans; Lacosamide; Levetiracetam; Male; Medical Audit; Mental Disorders; Middle Aged; Nitriles; Piracetam; Pregabalin; Prospective Studies; Pyridones; Retrospective Studies; Seizures; Sodium Channel Blockers; Topiramate; Young Adult