Tolerability of adjunctive eslicarbazepine acetate according to concomitant lamotrigine or carbamazepine use: A subgroup analysis of three phase III trials in adults with focal (partial-onset) seizures.

OBJECTIVE

To evaluate and compare the effects of concomitant lamotrigine (LTG) or carbamazepine (CBZ) on the incidence of treatment-emergent adverse events (TEAEs) in patients taking adjunctive eslicarbazepine acetate (ESL) for focal (partial-onset) seizures (FS).

METHODS

These post-hoc analyses of data pooled from three randomized, double-blind, placebo-controlled studies of adjunctive ESL (BIA-2093-301, -302 and -304) included adults (≥16 years) with FS refractory to 1-3 antiepileptic drugs (AEDs). Patients were randomized equally to placebo, ESL 400 mg (Studies 301 and 302 only), 800 mg, or 1200 mg once daily (8-week baseline, 2-week titration, and 12-week maintenance periods). TEAEs, TEAEs leading to discontinuation, and serious AEs (SAEs) were evaluated in patients taking, or not taking, LTG (excluding those taking CBZ or phenytoin [PHT]; i.e., the +LTG and -LTG/-CBZ subgroups), or CBZ (excluding those taking LTG or PHT; i.e., the +CBZ and -LTG/-CBZ subgroups) at baseline.

RESULTS

LTG was used concomitantly by 248 patients (+LTG; placebo, n = 81; ESL, n = 167) and CBZ by 613 patients (+CBZ; placebo, n = 172; ESL, n = 441); 361 patients were taking neither LTG nor CBZ (-LTG/-CBZ; placebo, n = 109; ESL, n = 252). The overall incidence of TEAEs with ESL (any dose) was numerically higher for +CBZ (77%) than for +LTG (73%) or -LTG/-CBZ (68%; statistical significance not tested). Among patients taking ESL, dizziness, diplopia, and vomiting were reported more frequently in the +CBZ subgroup (30%, 14%, and 10%, respectively) than in the +LTG (16%, 8%, 5%) or -LTG/-CBZ (11%, 3%, 5%) subgroups. The overall incidence of TEAEs leading to discontinuation with ESL was higher for +CBZ (21%) than for +LTG (13%) or -LTG/-CBZ (15%). Dizziness leading to discontinuation with ESL was reported more frequently in the +CBZ subgroup than in the +LTG or -LTG/-CBZ subgroups (9%, 3%, and 3%, respectively). The overall incidence of SAEs in patients taking ESL was comparable across subgroups (+LTG, 5%; +CBZ, 6%; -LTG/-CBZ, 5%). The results were similar when evaluating placebo-adjusted incidences.

CONCLUSION

There was a potential pharmacodynamic interaction between AEDs with a putatively similar mechanism of action, with a seemingly lesser interaction between ESL and LTG versus ESL and CBZ. If combining ESL with LTG or CBZ, clinicians should be aware of the potential risk for an increased incidence of TEAEs typically associated with voltage-gated sodium channel inhibitors (e.g., dizziness, blurred vision, vertigo, diplopia, headache, or vomiting).