We are all familiar with the classic ECG abnormalities caused by the sodium channel blocking properties of tricyclic antidepressants (QRS interval widening, R wave in aVR, S wave in I and aVL, and rightward deviation in terminal 40 msec of QRS). Here are some other medications that also block cardiac sodium channels in a similar manner:

• Cocaine
• Diphenhydramine
• Cyclobenzaprine (Flexeril)
• Carbamazepine (Tegretol)
• Phenothiazines
• Propoxyphene
• Class 1A antidysrhythmics (quinidine, procainamide, disopyramide)
• Class 1C antidysrhythmics (encainide, flecainide, propafenone, moricizine)
• Amantadine