Antiarryhthmics Flashcards
Quinidine Adverse
Class 1 Sodium channel blocker
**Cinchonism (named after tree that anti malarials come from-Quinines-so seen in any antimalarials only BUZZ WORD) - Tinnitus, ocular dysfunction (cannot tell if miosis or mydriasis because it is both a muscarinic and alpha blocker), CNS excitation, GI disturbances (same as eyes explanation)
Hypotension
Prolongation of QRS and QT interval - Torsades *****
Quinidine General
Class IA Sodium channel blocker
- muscarinic receptor blocker
- alpha bloc (possible reflex tachycardia)
- wide clinical use in many arrhthymias; in atrial fibrillation, need initial digitalization (to slow AV conduction)
Quinidine drug interactions
Class 1 sodium channel blocker
- Hyperkalemia enhances effects and vice versa
- Displaces digoxin from tissue binding sites
Procainamide Description
Class 1A Sodium channel blocker
- Less muscarinic receptor block than quinidine
- Metabolized through conjugation by N-acetyltransferase
- -therefore affected by slow/fast metabolizers
Procainamide Adverse
Class 1 Sodium channel blockers
SLE like syndrome
Hematotoxicity
CV effects (torsades)
Torsades caused by what type of drugs?
Anti muscarinic
SLE like syndrome is caused by what drugs?
Procainamide
Hydralazine (anti HTN)
Isoniazid (anti TB)
-seen in slow acetylators
Drug induced SLE lab results
Positive anti ANA
Positive anti histone** (specific to drug induced)
Negative anti dsDNA
Disopyramide
Class 1A sodium channel blocker
Class 1B Drugs
Sodium channel blockers
-Block fast sodium channels (decrease
-Block inactivated channels (slow conduction in hypoxic and ischemic heart) -slows cells ability to go back to resting
-Decrease APD - due to block of the slow sodium “window” currents
Lidocaine, Mexiletine
Lidocaine cardio uses
Class1 B
- post MI
- Open heart surgery
- Digoxin toxicity*
Lidocaine adverse
Class 1B CNS toxicity (seizures); least cardiotoxic of conventional anti arrhythmics ***IV only*** (due to first pass metabolism)
Mexiletine and Tocainide
Class 1B drugs
Same as lidocaine
Oral formulations
Class 1C
Second choice drug (only use if nothing else worked)
- block fast sodium channels especially His-Purinje tissue
- No effect on APD
- No ANS effect
Flecainide
Class 1C
Limited use becase of its proarrhthymic effects leading to sudden cardiac death
Last ditch drug … some will be saved but many may die too
Flecainide, Propafenone
Class II
Beta blockers (see ANS)
- decrease SA and AV nodal activity (parasymp dominance)
- decrease slope of phase 4
Class II Drugs
Beta blockers Non selective (propranolol) and selective (acebutolol, esmolol)
Class II Uses
Beta blockers
- negative inotropic effect decreases O2 demand so helpful to reduce reccurence of MI or prevent MI in general
- Prophylaxis post MI, supraventricular tachyarrhythmias (SVT)
- Esmolol (IV) is used in acute SVTs
Which beta blocker is used in treatment of acute supraventricular tachycardias but not for prophylaxis?
Esmolol
Esmolol is indicated for use in what?
Supraventricular tachycardia
Indicated for the rapid control of supraventricular tachycardias in patients with atrial fibrillation or atrial flutter in the peri or post operative setting where rapid, short term control of ventricular rate with an ultra short acting agent is indicated
The beta blockers have what as part of their antiarrhythmic mechanism of action?
Decrease cAMP levels
A patient is diagnosed with congenital long QT syndrome. If this patient is to be treated for cardiac arrhthymias, drugs with which mechanism would most likely be contraindicated?
Block potassium channels would be contraindicated Congenital long QT syndrome predisposes patients to torsades, therefore those individuals should avoid drugs that May also precipitate torsades. Both class 1A and Class III antiarrhythmic drugs may cause torsades because of their potassium channel blocking ability
A patient on antiarrhthymic drug therapy yexperiences syncopal episodes associated with a prolonged QT interval. The patient also suffers from diarrhea and gastrointestinal upset and complains of ringing in his ears. What drug was prescribed for this patient?
Quinidine
Torsades-K channel blocks
Cinchonism- quinines
Which antiarrhythmic drug is associated with an increase in mortality when usedprophylactically in ventricular tachycardia?
Flecainide
Class 1C antiarrhthymics -increased sudden death post MI
What Class 1 oral drugs preferentially target ischemic areas of the heart?
Class 1B
Mexiletine and Tocainide
Lidocaine is only IV
Compared with procainamide, which of the following effects is unique to quinidine? Hypotension Prolongation of the action potential Sodium channel block Systemic lupus erythematosus Torsades
Hypotension
Class IA Mechanism
-Block fast sodium channels
-Preferentially in the open or activated state
-Increase APD and ERP
-Also block potassium channel (prolongs repolarization)
Quinidine, Procainamide, Dispyramide
Class III Mechanism
Potassium channel blockers
-decreased I(k), slowing phase 3
-increase APD and ERP
Amiodarone, Ibutilide, Dofetilde, Sotalol “AIDS”
Amiodarone general
Class III Potassium Blocker Mimic classes I, II, III and IV Increases APD and ERP in all cardiac tissues Use-any arrhythmia half life - greater than 80 days
Amiodarone Side effects
High tissue and protein binding
- Pulmonary fibrosis (restrictive pulmonary disease)
- Blue pigmentation of the skin (smurf)
- photo toxicity
- corneal deposits
- hepatic necrosis
- thyroid dysfunction
Sotalol
Decreases I(k), slowing phase III
Beta one blockade, leading to decrease heart rate, decrease AV conduction
Use-life threatening ventricular arrhythmia
If a patient is prescribed sotalol for treatment of an arrhythmia, he was most likely diagnosed with what?
Ventricular fibrillation
A patient with recurrent supraventricular tachycardia is started on a new medication that has a risk of causing pulmonary fibrosis. What drug?
Amiodarone
The class III antiarrhythmics primarily slow what phase?
3
Class IV
L type Calcium channel blockers
- block slow cardiac Ca2+ channels
- decrease phase 0, decrease phase IV
- decrease SA, decrease AV nodal activity
Class IV drugs
Calcium channel blockers
Verapamil and diltiazem
Verapamil and Diltiazem Use
Supraventricular tachycardias
Verapamil and Diltiazem Side effects
VERAPAMIL CONSTIPATION**
AV block
Verapamil and Diltiazem Drug Interactions
- Additive AV block with beta blockers, digoxin
- Verapamil displaces digoxin from tissue binding sites
If a patient is prescribed verapamil for an arrhythmia she most likely has what?
Paroxysmal supraventricular tachycardia
Diltiazem effects what phase as an antiarrhythmic?
Decreases phase 4
Adenosine is antagonized by what?
Methylxanthines - theophylline (used in COPDs like asthma which can cause V-tach) and caffeine
Magnesium is used for what?
Torsades
Drugs that cause Torsades
Potassium channel blockers
Antimuscarinics -quinidine, antihistamines
Antipsychotics (Thioridazine)
Tricyclic antidepressants
Magnesium works how?
By antagonizing calcium
