Electrophysiological effects of flecainide enantiomers in canine Purkinje fibres

Naunyn-Schmiedeberg's Archives of Pharmacology
J K SmallwoodM I Steinberg

Abstract

Since flecainide is a chiral class I antiarrhythmic agent, we examined the basic electrophysiological effects of its enantiomers (10-(6) - 3 x 10(-5) mol/l) in isolated canine Purkinje fibres using standard microelectrode techniques. Frequency-dependent block was studied by pacing at cycle lengths of 300 and 2000 ms. Both enantiomers produced a marked, concentration-dependent decrease in maximum upstroke velocity (Vmax), with greater depression occurring at a cycle length of 300 ms. The concentration causing a 50% decrease in Vmax (EC50) at this pacing rate were 5.0 +/- 0.6 x 10(-6) mol/l for (+)-flecainide and 6.2 +/- 0.8 x 10(-6) mol/l for (-)-flecainide, and were not significantly different. Both enantiomers also produced a concentration- and frequency-dependent decrease in action potential amplitude and an increase in conduction time with no significant differences between the enantiomers. However, at the highest concentration studied (3 x 10(-5) mol/l), none of the nine tissues exposed to (+)-flecainide could be paced at 300 ms cycle length while five of eight tissues exposed to (-)-flecainide could be paced, suggesting the possibility of a small difference between the effects of the enantiomers on membrane responsiveness....Continue Reading

Citations

Aug 1, 1990·Naunyn-Schmiedeberg's Archives of Pharmacology·J K SmallwoodM I Steinberg
Apr 1, 1991·Pflügers Archiv : European journal of physiology·D TricaricoR Rüdel
Nov 6, 1998·British Journal of Clinical Pharmacology·T J Campbell, K M Williams

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