Final answer:
Class IC sodium channel blockers can have toxic side effects including proarrhythmia, heart block, and CNS effects such as dizziness and tremors.
Step-by-step explanation:
Class IC sodium channel blockers, such as flecainide and propafenone, are antiarrhythmic drugs used to treat abnormal electrical activity in the heart. While these medications can be effective in managing certain types of arrhythmias, they can also have toxic side effects. Some of the toxicities associated with Class IC sodium channel blockers include proarrhythmia (causing new or worsening arrhythmias), heart block, and exacerbation of heart failure. These medications can also cause CNS effects, such as dizziness and tremors.