Possible Interaction: Flecainide and Quinidine

“These findings suggest that quinidine inhibits the first step of flecainide metabolism, although it may also reduce its renal clearance, but to a lesser extent (3.5 vs 2.9 ml·min−1·kg−1).The effects of flecainide on ECG intervals were not altered by quinidine.”

“Thus, quinidine tends to shift extensive metabolizer status for flecainide towards poor metabolizer status and may also alter its renal excretion.”

“A greater than 80% reduction of total ventricular ectopic depolarizations was obtained in eight of nine patients given flecainide and in five of ten patients given quinidine (p = 0.09).”

“The uptake of flecainide into intestinal epithelial LS180 cells was decreased significantly by acidification of the extracellular medium, and was inhibited by tertiary amines, such as diphenhydramine and quinidine.”

“We also compared the inhibitory potency of FLEC with other Class I agents: quinidine (QUIN, Class Ia); lignocaine (LIG, Class Ib) and propafenone (PROPAF, Class Ic).”

“Uptake transporter substrate assay revealed that flecainide (1 µM) showed 1.11-fold accumulation though the hMATE1-related active transport was significantly decreased in the presence of quinidine (42.0 ± 23.9 vs. 11.8 ± 4.1 pmol/mg in transfected cells; p < 0.05).”

“ Quinidine (10 μm) prevented VT in six out of six flecainide‐treated WT and 13 out of the 16 arrhythmogenic Scn5a+/− hearts in parallel with its clinical effects.”

“Although propafenone had little effect on the rate of ITO recovery … PROPAFENONE = 84 +/- 9 ms), ITO recovery in the presence of flecainide … quinidine was biexponential; it exhibited an additional slow component (tau FAST = 67 +/- 5 ms …; tau FAST = 55 +/- 5 ms and tau SLOW = 871 +/- 99 ms for quinidine).”

“The greatest contributing factor for quinidine was an increased effective refractory period/APD ratio, for lidocaine a slower restitution and for flecainide and mexiletine the shift of the restitution curve.”