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Old 06-20-2013
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Drug Side Effects of Anti-Arrythmics

Most of the anti arrhythmics are pro-arrhythmic especially class I anti arrhythmics like Digoxin, but we still use them. Are the effects dose dependent or is it rare to see a drug induced arrhythmia?
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Old 06-20-2013
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Depends on the drug in question. Certain drugs are not pro-arrhthmic and you should know which ones. Such as the drugs working on depolarized tissues.

Ia: can lead to torsades de pointes if the patient has a predisposing condition such that it's blocking k+ efflux or the patient is on medications that already prolonging his QT such as certain macrolides.
Ib: not pro-arrhythmic but only works on infarcted tissues. Increased risk of seizures though.
Ic: As Dr. Raymond says, we only give this to the patient as a last resort hail mary pass.
II: B-blockers associated with heart block acting on nodal cells phase 4. Delay depolarization.
III: all of them associated with Prolonged QT except amiodarone which is protective for torsades. So if you were to give a patient dofetilide or ibutilide who has a predisposition to prolonged QT, doesn't matter the dose. They could develop a polymorphic ventricular rhythm.
IV: Ca2+ channel blockers (Verapamil) associated with heart block. Only verapamil and dilitazem. Almodipine is not an anti-arrhythmic. If anything it's pro-arrhytmic from reflex tachycardia.
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Old 06-23-2013
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Thank you so much. I appreciate it.
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