Lidocaine and flecainide

These principles are important in understanding additive drug combinations (e.g., quinidine and mexiletine), antagonistic combinations (e.g., flecainide and lidocaine), and potential antidotes to excess sodium channel blockade (e.g., sodium bicarbonate or propranolol). They also explain a number of clinical observations, such as why lidocaine-like drugs are relatively ineffective for supraventricular tachycardia. The type Ib drugs are fast on/off, inactivated sodium blockers atrial cells, however, have a very brief inactivated phase relative to ventricular tissue. 

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