Eslicarbazepine Acetate 200 mg · Tablets

Eslicarbazepine acetate is extensively converted to eslicarbazepine, which is considered to be responsible for therapeutic effects in humans. The precise mechanism(s) by which eslicarbazepine exerts anticonvulsant activity is unknown but is thought to involve inhibition of voltage-gated sodium channels.

The pharmacokinetics of eslicarbazepine is linear and dose-proportional in the dose range of 400 mg to 1600 mg once daily, both in healthy adult subjects and patients. The apparent half-life of eslicarbazepine in plasma was 13 to 20 hours in adult epilepsy patients. Steady-state plasma concentrations are attained after 4 to 5 days of once daily dosing.

Absorption — Eslicarbazepine acetate is mostly undetectable (0.01% of the systemic exposure) after oral administration. Eslicarbazepine, the major metabolite, is primarily responsible for the pharmacological effect of eslicarbazepine acetate. Peak plasma concentrations (Cmax) of eslicarbazepine are attained at 1 to 4 hours post-dose. Eslicarbazepine is highly bioavailable, because the amount of eslicarbazepine and glucuronide metabolites recovered in urine corresponded to more than 90% of an eslicarbazepine acetate dose. Food has no effect on the pharmacokinetics of eslicarbazepine after oral administration of eslicarbazepine acetate.

Distribution — The binding of eslicarbazepine to plasma proteins is relatively low (<40%) and independent of concentration. In vitro studies have shown that plasma protein binding was not relevantly affected by the presence of warfarin, diazepam, digoxin, phenytoin, or tolbutamide. Similarly, the binding of warfarin, diazepam, digoxin, phenytoin or tolbutamide was not significantly affected by the presence of eslicarbazepine. The apparent volume of distribution of eslicarbazepine is 61 L for body weight of 70 kg based on population PK analysis.

Metabolism — Eslicarbazepine acetate is rapidly and extensively metabolized to its major active metabolite eslicarbazepine by hydrolytic first-pass metabolism. Eslicarbazepine corresponds to 91% of systemic exposure. The systemic exposure to minor active metabolites of (R)-licarbazepine is 5% and oxcarbazepine is 1%. The inactive glucuronides of these active metabolites correspond to approximately 3% of systemic exposure.

In in vitro studies in human liver microsomes, eslicarbazepine had no clinically relevant inhibitory effect on the activity of CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1, and CYP3A4, and only a moderate inhibitory effect on CYP2C19. Studies with eslicarbazepine in fresh human hepatocytes showed no induction of enzymes involved in glucuronidation and sulfation of 7-hydroxy-coumarin. A mild activation of UGT1A1-mediated glucuronidation was observed in human hepatic microsomes.

No apparent autoinduction of metabolism has been observed with eslicarbazepine acetate in humans.

Excretion — Eslicarbazepine acetate metabolites are eliminated from the systemic circulation primarily by renal excretion, in the unchanged and glucuronide conjugate forms. In total, eslicarbazepine and its glucuronide account for more than 90% of total metabolites excreted in urine, approximately two thirds in the unchanged form and one third as glucuronide conjugate. Other minor metabolites account for the remaining 10% excreted in the urine. In healthy subjects with normal renal function, the renal clearance of eslicarbazepine (approximately 20 mL/min) is substantially lower than glomerular filtration rate (80 to 120 mL/min), suggesting that renal tubular reabsorption occurs. The apparent plasma half-life of eslicarbazepine was 13 to 20 hours in epilepsy patients [see Dosage and Administration (2.4) and Use in Specific Populations (8.6)].

Geriatric Patients (≥65 Years of Age) — The pharmacokinetic profile of eslicarbazepine was unaffected in elderly subjects with creatinine clearance >60 mL/min compared to healthy subjects (18 to 40 years) after single and repeated doses of 600 mg eslicarbazepine acetate during 8 days of dosing. No dose adjustment is necessary in adults based on age, if CrCl is ≥50 mL/min.

Pediatric Patients (4 to 17 Years of Age) — A pharmacokinetic study of eslicarbazepine acetate was performed in 29 pediatric patients with partial-onset seizures.

Limited pharmacokinetic sampling was also performed during controlled pediatric adjunctive therapy partial-onset seizure studies. As in adult patients, eslicarbazepine acetate is rapidly and extensively metabolized to its major active metabolite eslicarbazepine. The pharmacokinetics of eslicarbazepine is linear and dose-proportional in the dose range of 5 to 30 mg/kg/day. Peak plasma concentrations (Cmax) of eslicarbazepine are attained at 1 to 3 hours post-dose.