Anti arrhythmic drugs.

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30 Sep 2016 - General


This doubt has troubled me since my 3rd year of med school .We classify these drugs according to the effect they have on the cardiac action potential (duration).I think we would all agree that some drugs prolong the duration action potential thus prevent arrhythmia but there is an exact opposite  class of drugs which decreases the duration of action potential but are still anti-arrhythmic .

This to me is  very confusing .Can someone help me out?

Ia -Quinidine, procainamide, disopyramide (depress phase 0, prolonging repolarization)
Ib -Lidocaine, phenytoin, mexiletine (depress phase 0 selectively in abnormal/ischemic tissue, shorten repolarization)
Ic -Flecainide, propafenone, moricizine (markedly depress phase 0, minimal effect on repolarization)
well If you see the above classification of drugs the
1a group prolongs repolarisation
1b.shortens it.
1c has minimal effect .
But all of them are antiarrhy...
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