Effect of lacosamide on the steady-state pharmacokinetics of digoxin: results from a phase I, multiple-dose, double-blind, randomised, placebo-controlled, crossover trial

Recent data suggest that P-glycoprotein may be involved in cellular transport of lacosamide. To investigate potential drug–drug interactions (DDIs) between lacosamide and digoxin, this phase I, multiple-dose, randomised, double-blind, placebo-controlled, crossover trial assessed the pharmacokinetics, pharmacodynamics, safety and tolerability of digoxin administered in combination with lacosamide or placebo. Twenty healthy White male volunteers were randomised. After receiving digoxin 0.25 mg three times daily on day 1 (loading dose), participants received digoxin 0.25 mg once daily on days 2–22. Participants received either lacosamide (200 mg twice daily) or placebo on days 8–11 and vice versa on days 18–21, after a 6-day washout. The steady-state area under concentration–time curve over the dosing interval (AUC24,ss) and maximum steady-state plasma concentration (C max,ss) of digoxin were measured; ratios of these parameters for co-administration of digoxin + lacosamide versus digoxin alone were used to evaluate potential DDIs. Interaction was excluded if the 90 % confidence interval (CI) for the geometric mean ratio of AUC24,ss and C max,ss fell within the acceptance range for bioequivalence (0.8–1.25). The point estimates (90 % CI) of the geometric mean ratios for co-administration of digoxin with lacosamide versus digoxin alone for AUC24,ss [1.024 (0.979–1.071)] and C max,ss [1.049 (0.959–1.147)] were within the acceptance range for bioequivalence. Digoxin and lacosamide co-administration was generally well-tolerated. A small numerical increase in the mean PR interval following co-administered digoxin + lacosamide was observed versus digoxin alone and versus pre-treatment baseline values (178.5 vs. 170.4 or 166.8 ms, respectively). The RR interval increased in parallel. The change was not considered clinically relevant. Co-administration of steady-state digoxin (0.25 mg/day) with multiple-dose lacosamide (400 mg/day) versus digoxin alone revealed no differences in digoxin disposition.