test 2 drugs part a Flashcards
Quinidine
▪ Sodium Channel Blockers -Class Ia
▪ Been around forever
▪ Orally
▪ Various tachyarrhythmias (atrial tach, juntional tach, and vent tach)
▪Rarely used
▪ Toxic side effects
▪ Chinconism
▪ Torsades de pointesDisopyramide (Norpace)
▪ Sodium Channel Blockers -Class Ia
▪ Action
▪ Slows conduction velocity
▪ Increases refractoriness
▪ Only approved for ventricular arrhythmias
▪ More negative inotropic effects and peripheral vasoconstriction
▪ You do NOT want these effects with a sick heart
- third line drug
Procainamide
▪ Most widely used from class Ia
▪ Derived from procaine (local anesthetic)
▪ Oral, IV, IM
▪ Has direct depressant actions on SA and AV nodes
▪ Adverse effects similar to Quinidine but less severe
▪ May cause or aggravate lupus erythematosus
Lidocaine (Xylocaine)
▪ Sodium Channel Blockers -Class IB
▪ Local anesthetic
▪ Only given IV
▪ Wide therapeutic index
▪ Major toxic side effect (at high doses) is cardiac depression
▪ Extends refractory period further into diastole in depressed cardiomyocytes than in healthy ones
* D.O.C. for ventricular arrhythmias, particularly those associated with “sick hearts” post-MI
▪ Frequently used as a component of
cardioplegia
▪ Suppresses arrhythmias (PVC)
Lidocaine Dosing
▪ IV bolus 1-2 mg/kg
▪ Usually 100 to 200 mg bolus at XC removal
▪ Not to exceed 300 mg/hr
▪ Duration of action: 15-30 minutes
Mexiletine
▪ Sodium Channel Blockers -Class IB
▪ Like an oral Lidocaine
▪ Used in the treatment of ventricular arrhythmias
Flecainide
▪ Sodium Channel Blockers -Class IC
▪ Suppresses Phase 0 upstroke in Purkinje fibers and cardiomyocytes
▪ Dramatically slows conduction and automaticity is decreased via an increase in the threshold potential
▪ Oral
▪ Used for refractory ventricular arrhythmias
▪ Particularly PVCs
▪ Negative inotropic effects worsen CHF
- Recent studies suggest Flecainide is more likely to harm than help in the long-run
Propafenone (Rythmol)
▪ Sodium Channel Blockers -Class IC
▪ Slows action potential
▪ Oral
▪ Considered to be a “broad spectrum” antiarrhythmic but used primarily for supraventricular tachyarrhythmias
Propranolol (Inderal)
▪ Class II β-Blockers
▪ Has been proven to decrease incidence of mortality within the first year of an MI
Metoprolol (Lopressor)
▪ Class II β-Blockers
▪ The most commonly used β-blocker for treating cardiac arrhythmias
▪ Less β₂ than Inderal
Esmolol (Brevibloc)
▪ Very short-acting IV β- blocker commonly used during surgery and during emergencies
Amiodarone (Cordarone)
▪ Class III Potassium Channel Blockers
▪ Contains iodine and is structurally similar to thyroxine
▪ Affects all cardiac tissue, so it has a broad spectrum of activity
Often the drug of choice for A-fib
▪ Treatment of
▪ Severe refractory supraventricular and ventricular tachyarrhythmias (2nd line)
▪ ATRIAL FIBRILLATION
▪ Atrial flutter
▪ Very long half life (20-100 days)
▪ High ability to interact with other drugs
▪ A lot of side effects (particularly with long term use)
▪ Less toxicity at lower dosages (100-200 mg/day)
▪ Takes weeks to months to get to therapeutic levels
▪ High loading dose necessary
▪ Potential for side effects increases with both high doses and long term use
Amiodarone (Cordarone) side-effects
▪ Liver damage ▪ GI upset ▪ Thyroid dysfunction ▪ Blue skin ▪ Dizziness ▪ Neuropathy ▪ Corneal deposits and optic neuritis
Dronedarone
▪ Class III Potassium Channel Blockers
▪ Similar to Amiodarone without the iodine
▪ (less thyroid dysfunction and blue skin)
▪ Shorter half life (24 hours)
▪ Used for A-fib or A-flutter, but less effective than Amiodarone
▪ Fewer side effects… EXCEPT…..
- This drug can be deadly so its usage is limited!
Sotalol (Betapace, Sorine)
▪ Class III Potassium Channel Blockers
▪ Class III antiarrhythmic and non-selective β-blocker
▪ Not only does it reduce post-MI mortality (as do most β-blockers), it lengthens the refractory period
▪ Uses
▪ Life threatening ventricular arrhythmias
▪ Atrial fibrillation
▪ Pediatrics
▪ Reduces myocardial oxygen consumption AND acts as powerful antiarrhythmic
▪ Helps prevent fibrillation and makes defibrillating patients easier
▪ Ideal for post-MI patients
- accumulates less deaths per year compared to other drugs
Dofetilide (Tikosyn)
▪ Class III Potassium Channel Blockers
▪ Pure potassium channel blocker
▪ Often drug of choice for persistent A-fib with heart failure or coronary artery disease
▪ Inpatient initiation only
Ibutilide (Corvert)
▪ Class III Potassium Channel Blockers
▪ Class III AND Ia properties
▪ Drug of choice for chemical conversion of atrial flutter and fibrillation
- you usually get shocked instead
Verapamil and Diltiazem (Cardizem)
▪ Used interchangeably for arrhythmias
▪ “Use-dependent”
▪ Preferentially block channels on tissues depolarizing too fast
▪ Block Ca++ channels most effectively on the AV and SA nodes
▪ Reduce ventricular rate in atrial flutter & fibrillation
▪ Rarely converts
▪ Occasionally useful in ventricular arrythmias
▪ Negative inotropes
▪ Clinical usefulness limited in diseased hearts
Digoxin
▪ Inhibits the Na+/K+ ATPase pump in myocardial cells
▪ Prolongs the effective refractory period and diminishes the conduction velocity in the AV node
▪ Used to control ventricular response rate in A-fib and A-flutter
- decreases firing of SA node
Adenosine (Adenocard)
▪ Decreases conduction velocity ▪ Prolongs refractory period ▪ Decreases automaticity in AV node ▪ D.O.C for abolishing Supraventricular tachy ▪ VERY short half life (~10-15 seconds) ▪ Causes transient hypotension
Adenosine (Adenocard) dose
- *First dose is 6mg fast IV push**
* *If that doesn’t convert the SVT, give 12 mg fast IV push**
Magnesium Sulfate
▪ Magnesium is necessary for the transport of Na+, Ca++ and K+ across cell membranes
▪ IV
▪ Slows the rate of SA node impulse formation
▪ Prolongs conduction time along the myocardial tissue
D.O.C for torsades de pointes and digoxin-induced arrhythmias
MgSO4 Dosing
▪ 2 to 2.5 g initial bolus
▪ 1.75 g/h infusion
▪ On CPB, usually given as 2 to 4 grams at XC removal with Lidocaine
▪ Often 0.5 g/mL concentration
