text: However, pretreatment with agents that block late I(Na), like lidocaine, mexiletine, and << RSD1235 >>, a novel mixed [[ ion channel ]] blocker for the rapid pharmacologic conversion of atrial fibrillation, significantly attenuates the prolonging effects of Class III agents or those induced by ATX-II, a specific toxin that delays Na channel inactivation and amplifies late I(Na) greatly, mimicking LQT3.