Effect of oral cibenzoline on steady-state digoxin concentrations in healthy volunteers

The effect of oral cibenzoline on steady-state digoxin concentrations was studied in 12 healthy subjects ranging from 41 to 55 years of age. Each subject received an oral dose of 0.25 mg or 0.375 mg digoxin once daily for 27 days. On days 14 to 21, 160 mg of oral cibenzoline were administered concomitantly every 12 hours for a total of 15 doses. Plasma digoxin concentration-time profiles obtained before, during, and after cibenzoline coadministration were compared to determine the effect of oral cibenzoline on steady-state digoxin concentrations. The maximum plasma concentration, time of maximum concentration, area under the curve during a dosing interval and steady-state trough plasma concentration for digoxin, during and after concomitant doses of cibenzoline were similar to those before administration, indicating that cibenzoline did not affect the pharmacokinetics of digoxin. In addition, plasma cibenzoline concentration-time profiles after the first and last dose of cibenzoline were similar to those observed in previous studies in which multiple doses of cibenzoline alone were administered. The results of this study indicate that there is no pharmacokinetic interaction between digoxin and cibenzoline when the two drugs are coadministered to healthy subjects in multiple doses.