K Channel Blockers (Anti-Arrhythmias)

Question 1

Amiodarone

Answer 1

MOA:
– ↑APD, refractoriness
– Some have properties of other classes

Most important thing to remember:
– ↑QTc –> risk of Torsades de Pointes
– Especially when combined with other QTc prolonging drugs (antipsychotics, fluoroquinolones, macrolides, more…)

Availability:
- PO & IV

Toxicity/Pearl:
- Properties of all four VW classes
- Serious AE’s, some permanent
– Pulmonary fibrosis, thyrotoxicity, neurotoxicity, hepatotoxicity, and more…
- Lots of DDI’s, long T1/2 (up to 50 days!)

Question 2

Dofetilide

Answer 2

MOA:
– ↑APD, refractoriness
– Some have properties of other classes

Most important thing to remember:
– ↑QTc –> risk of Torsades de Pointes
– Especially when combined with other QTc prolonging drugs (antipsychotics, fluoroquinolones, macrolides, more…)

Availability:
- PO

Toxicity/Pearl:
↑↑QTc –> requires inpatient initiation
– (Restricted distribution program)

Question 3

Sotalol

Answer 3

MOA:
– ↑APD, refractoriness
– Some have properties of other classes

Most important thing to remember:
– ↑QTc –> risk of Torsades de Pointes
– Especially when combined with other QTc prolonging drugs (antipsychotics, fluoroquinolones, macrolides, more…)

Availability:
- PO & IV

Toxicity/Pearl:
Beta blocker properties
CI’s: decompensated CHF, asthma, COPD
↑↑QTc –> requires inpatient initiation

Question 4

Dronedarone

Answer 4

MOA:
– ↑APD, refractoriness
– Some have properties of other classes

Most important thing to remember:
– ↑QTc –> risk of Torsades de Pointes
– Especially when combined with other QTc prolonging drugs (antipsychotics, fluoroquinolones, macrolides, more…)

Availability:
- PO

Toxicity/Pearl:
CI’s: CHF, CAD, & permanent AF (↑mortality)
– (FDA approved for AF / AFL only)

Question 5

Ibutilide

Answer 5

MOA:
– ↑APD, refractoriness
– Some have properties of other classes

Most important thing to remember:
– ↑QTc –> risk of Torsades de Pointes
– Especially when combined with other QTc prolonging drugs (antipsychotics, fluoroquinolones, macrolides, more…)

Availability:
- IV

Toxicity/Pearl:
For cardioversion, not maintenance treatment
Inpatient use only