Antiarrythmics Class 3 Flashcards
What channel does class 3 drugs affect?
How does this action affect the cells?
Blocks K channels (inward rectifier K channels)
Blocking this channel SLOWS repolarization. This increases both the AP duration and effective refractory period.
(This means that the cells are “unexcitable” for longer)
Amiodarone is a Class 3 drug, but it is not very specific. Name it’s effects on things other than K channels:
Potent Na channel blocker
Weak beta-blocker
Weak Ca Channel blocker
What are amiodarone’s adverse side effects?
What about general toxicities?
(There is a lot of stuff for this question…)
Adverse:
- Pulmonary Toxicity (the biggie)
- Abnormal liver function
- photodermatitis (blue-gray skin)
- Corneal microdeposits (halos, optic neuritis)
- Hypo/Hyper- Thyroid
Toxicity:
- Bradycardia/heart block in pts with preexisiting SA/AV node probs
- Blocks conversion of thyroid hormones
Amiodarone also has a mean list of pharmacokinetics…
Try to list out the most important parts.
- Substrate for CYP3A4
- Inhibits several CYP450 (so can have increased levels of statins, digoxin, and warfarin)
What is the main therapeutic use of Amiodarone?
For ventricular tachycardia (including V-fib)
Effective for A-fib and A-flutter
Therapeutic uses for dofetitilide?
Maintenance and restoration of normal sinus rhythm in atrial fibrillation. Contraindicated in long QT, bradycardia, hypokalemia
What other channels does dofetilide block other than K?
Trick question. Dofetilide is very selective to K.
Pharmacokinetics of dofetilide?
100% bioavailable! Hepatic metabolism via CYP3A4
Does dofetilide can any toxicity?
Can cause life-threatening arrhythmias!
Now let’s talk about ibutilide… any crazy toxicities?
excessive QT-interval prolongation and torsades de pointes. Can cause life-threatening ventricular arrhythmias
What do you use Ibutilide for?
Acute conversion of atrial flutter and fibrillation to normal sinus rhythm. More effective in flutter…
