Cardio: Class III Antiarrhythmics

Question 1

The potassium current is found in which phases of the cardiac action potential?

Answer 1

2 (during which it competes with calcium) and 3 (during which it repolarizes the cell)

Question 2

What is the mechanism of class III antiarrhythmics?

Answer 2

They block potassium channels, thus prolonging both depolarization and repolarization of the His-Purkinje fibers and cardiac myocytes. (Think of the mariachi singer throwing aside the banana curtain, thus flattening out the action-potential wave.)

Question 3

The class III antiarrhythmics uniquely share ______________.

Answer 3

some properties of all the categories of drugs: they block inactivated sodium channels (I), block beta-receptors (II), and block calcium channels (IV) (Think of the three singers counting off “uno dos tres cuatro!”)

Question 4

What suffix is common in the class III drugs?

Answer 4

-tilide (as in dofetilide and ibutilide)(Think of the “TILl I DiE” marriage proposal to the girl sitting at the table.)

Question 5

Which class III drug has a lot of beta-blocking ability?

Answer 5

Sotalol (Think of the guy knocking over soda bottles with his beta-bugle.)

Question 6

Which arrhythmias are treatable with class III drugs?

Answer 6

Both supraventricular (atrial) and ventricular arrhythmias, such as atrial fibrillation (they specifically control the rhythm of atrial fibrillation)

Question 7

What neurologic side effects does amiodarone have?

Answer 7

Tremor, ataxia, neuropathy, and sleep disturbances

Question 8

What is symbolized by the singers’ glasses?

Answer 8

The fact that amiodarone can cause gray corneal deposits (in almost all patients with a couple weeks)

Question 9

True or false: amiodarone causes hyperthyroidism.

Answer 9

True, but it can also cause hypothyroidism! (Think of the two singers: one has an untied bowtie, and the other has a large, tied bowtie.)

Question 10

What cardiopulmonary side effects does amiodarone have?

Answer 10

Pulmonary fibrosis (duh); heart block (represented by the singer’s heart-block-shaped hat); and torsades (like every potassium-channel-blocking agent) –though dofetilide, ibutilide, and sotalol are more likely to cause torsades(Think of the twisting banners everywhere.)

Question 11

Dermatologically, amiodarone can _______________.

Answer 11

cause gray-blue discoloration in sun-exposed areas

Question 12

What hepatic effects does amiodarone have?

Answer 12

It can cause hypersensitivity hepatitis, and it is an inhibitor of CYP450.