ARRHYTHMIAS-VT DRUGS

SUMMARY

1. Class 1: Sodium channel blockers that slow electrical conduction in the heart.

2. 1a: Quinidine, procainamide, disopyramide-slow conduction velocity, prolongs action potential duration, and can prolong QT interval.

3. 1b: Lidocaine, tocainide, mexiletine, phenytoin-shorten action potential duration slightly with no significant QT prolongation.

4. 1c: Flecainide and propafenone-slow conduction veloc­ity without effect on potential duration or QT interval.

5. Class II: Beta-blockers-decrease heart rate and blood pressure by blocking impulses that can cause irregular heart rhythm and decreasing hormonal effects (e.g. adrenaline) on the heart.

6. Class Ill: Amiodarone, sotalol, and the newer agents, dofetilide (oral Tikosyn®) and dronedarone (Multaq®:­ prolong the action potential by potassium channel blockade. These agents can cause QT prolongation. Note: See side effects on dronedarone below.

7. Class IV: Calcium channel blockers, especially vera­pamil and diltiazem, slow inward current. They decrease heart rate and blood pressure like class II.

Reference(s)

Wilkinson, I., Furmedge, D. and Sinharay, R. (2017). Oxford handbook of clinical medicine. Oxford: Oxford University Press. Get it on Amazon.
Feather, A., Randall, D. and Waterhouse, M. (2020). Kumar And Clark’s Clinical Medicine. 10th ed. S.L.: Elsevier Health Sciences. Get it on Amazon.
Hannaman, R. A., Bullock, L., Hatchell, C. A., & Yoffe, M. (2016). Internal medicine review core curriculum, 2017-2018. CO Springs, CO: MedStudy.
Therapeutic Guidelines. Melbourne: Therapeutic Guidelines Limited. https://www.tg.org.au [Accessed 2021].