Class IB antiarrythmics question

[pistachio]

Does anyone have a reasonable explanation for why this class shortens AP duration?

Much obliged.

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[MedLover25]

We just did these today in class, and here's what I got out of class:

They block and release between each Action Potential. (block inactivated fast Na channels)
No effect on conduction

And the big thing was --> ****No significant effect on Action Potential Duration. THEY DO NOT INCREASE APD

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probably didn't answer your question, but I'm behind in class so I haven't caught up to this lecture yet; just wanted to share what i knew

 

[preilijuly]

A major distinguishing characteristic of class IB antiarrhythmics is their fast dissociation from Na channel proteins. (Source: Dudek "HY Cell and Molecular Biology", 2nd ed; p10).
Would it make sense answering your question?

 

[pistachio]

Thanks guys!

I found this in Lilly: "The shortening of the AP is attributed to blockade of small Na+ currents that normally continue through phase 2 of the action potential."

That one was driving me crazy!!!