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Antiarrhythmic Drugs

Drugs used in the treatment of arrhythmias suppress abnormal impulse formation or conduction

Sodium channel blockers

preferentially bind and block Na channels in damaged, rapidly firing cardiac tissue
converts one-way block into two-way block
lidocaine

Beta blockers

inhibit sympathetic innervation, slowing HR, decreasing conduction velocity through AV node, and increasing refractory period
metoprolol

Increase action pulse duration

work by increasing refractory period
leads to two-way block
many of these drugs block K+ channels involved in repolarizing
amiodarone

Calcium channel blocker

decrease AV node velocity and increase refractory period
verapamil
diltiazem

Other

decrease AV node velocity and increase refractory period
digoxin
adenosine

Bradycardia due to a damaged SA node can be treated with:

atropine, a muscarinic blocker that increases transmission rate
epinephrine or dobutamine to stimulate β1 receptors