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Will procainamide increase QT interval?

by egpat        Posted on 09-06-2017

Yes. Class Ia agents like quinidine, procainamide, disopyramide are proarrhythmic agents that can increase QT interval predisposing to torsade de pointes.

These agents show major action by blocking voltage gated sodium channels.That's why they are classified as class I agents. Proarrhythmic action of class I antiarrhythmic agents leading to torsade de pointes

At the same time, they also show potassium channel blocking activity. Since they have class III activity , the effective refractory period increases leading to increased QT interval in ECG and may precipitate torsade de pointes.

Torsade de pointes due to class III action increasing QT interval

Procainamide is a class Ia antiarrhythmic agent that also shows class III activity by blocking the potassium channels.

Torsade de pointes due to N-acetyl procainamide

Procainamide is metabolized by N-acetylation forming an active metabolite N-acetyl procainamide which shows class III activity.


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