Abstract
In order to determine the relationship between efficacy and plasma level of flecainide in ventricular premature contractions (VPC), a study was carried out through multipleadministration method in 15 patients with VPC at dose level of 50mg b.i.d., 100mg b.i.d., or 150mg b.i.d. The results of this study were as follows.
1) Flecainide was effective in 50% of patients at 50mg b.i.d. and all patients at 100 mg b.i.d. and 150mg b.i.d. Judging from the supression ratio of VPC by flecainide, the dose level from 50mg b.i.d. to 100mg b.i.d. seems to be appropriate for clinical applications.
2) The minimum effective plasma level may be placed at 200ng/ml, and a reliable suppressive effect on VPC can be expected of flecainide at plasma level of 400ng/ml or more.
3) Plasma level at steady state increased dose dependently up to 100mg b.i.d., though the plasma level at 150mg b.i.d. was greatly elevated to the extent of 1, 000ng/ml or more.
4) Six laboratory data in 3 patients showed abnormal values, but the elevations in GOT, GPT and BUN seemed to have slight if any relationship to the treatment. The PQ and QTc intervals on the electrocardiogram were prolonged significantly.
Therefore, it may be concluded that flecainide is a useful drug for the treatment of VPC and that 100mg b.i.d. is suitable as a usual clinical dose.
