Antiarrhythmic Drugs Flashcards
Digoxin
- Antiarrhythmic effect is on the what?
- Used for what?
- Used for it’s effect on?
- AV node
- ventricular rate control in atrial fibrillation and flutter
- positive inotrope effect in CHF
- Digoxin_____ the electrical conduction through the AV node
- Stimulates the ____________ nervous system and increases ______ ______
- slows
- parasymathetic
vagal tone
Slows AV conduction and prolongs the AV nodal refractory period. What does this cause on the EKG? 3
- Increased PR interval
- Downward sloping ST segment depression
- Shortened QT interval
Dig is used to slow ventricular rates in Afib and A flutter. What is the downside to this? 2
Slows rates (for rate control)!!!
- Does NOT convert rhythms (afib/flutter) to sinus!
- Does not work well for slowing ventricular rates during exercise!
Digoxin:
- Onset?
- Administration/dosing?
- Steady State?
- Theuropeutic range?
- Slow onset
- Need a loading dose period
- May take a week to achieve steady state
- Monitor serum blood levels periodically
Therapeutic range 0.8 – 2 ng/mL
AF and concomitant LVSD is 0.5-1 ng/mL
Who has increased mortality on Dig?
Higher levels in pts with LVSD = higher mortality
AF and concomitant LVSD is 0.5-1 ng/mL
Digoxin toxicity can be caused by
3
- Declining renal function
Renal excretion - Electrolyte disturbances
- Drug interactions
Many meds may increase serum digoxin concentrations
What electrolyte disturbances can cause dig toxicity? 3
What drug interactions may increase serum dig concentrations? 2
- Hypokalemia,
- hypomagnesemia and
- hypercalcemia
can predispose the myocardium to the toxic effects of digoxin
- amiodarone,
- verapamil
Signs and symptoms of digoxin toxicity
8
- Heart block
- AV junctional tachycardia
- Ventricular arrhythmias
- Visual disturbances
- Blurred vision, yellow/green halos
- Dizziness
- Weakness
- GI: N/V/D and anorexia
Why is adenosine used?
Used to convert PSVT to SR
- Activates _______ channels by increasing the outward ________ current
- __________ the membrane potential and __________ spontaneous SA node depolarization
- _______ automaticity and conduction in the SA and AV nodes
- Half life?
- potassium
- potassium
- Hyperpolarizes
- decreases
- Inhibits
- 10 seconds
Adenosine contraindications
2
- 2nd or 3rd degree heart block
2. sick sinus syndrome in the absence of a pacemaker
- What kind of drug is atropine?
2, What does it enhance and how? 2
- What does it block? 2
- Used for the treatment of what?
- May induce what?
- Parasympatholytic drug
- Enhances
- -sinus nodal automaticity and
- -AV nodal conduction through direct vagolytic action - Block
- -acetylcholine and
- -parasympathetic neuroeffector sites - Used for the treatment of symptomatic bradycardia
- May induce tachycardia
Atropine contraindications
4
- Angle closure glaucoma
- Obstructive uropathy (think BPH)
- Tachycardia
- Bowel obstruction or altered bowel transit time
Class 1 blocks what?
What are the sub classes?
3
sodium channel blockers
- Class Ia (intermediate onset/offset)
- Class Ib (fast onset/offset)
- Class Ic (slow onset/offset)
Class Ia (intermediate onset/offset)
are which drugs?
3
- Disopyramide (Norpace)
- Procainimide (Pronestyl)
- Quinidine (Quinidex)
Class Ib (fast onset/offset) are which drugs? 3
- Lidocaine
- Mexiletine (Mexitil)
- Phenytoin (Dilantin)
Class Ic (slow onset/offset) are which drugs? 2
- Flecainide (Tambocor)
2. Propafenone (Rythmol)
3 classes of sodium channel blockers are categorized how? 2
- Subdivided by the rate of sodium channel dissociation
2. Variable rates of binding and dissociating from the sodium channel receptor
- What kind of drugs are Class Ia?
- What are they used to treat? 2
- They have anticholinergic effects that can lead to?
- WHat do you need to prescribe with this?
- Major complication?
- Which drug is IV only?
- These drugs are proarrhythmic
Used to treat atrial and ventricular rhythms
- Ex: Quinidine and Disopyramide increase automaticity of the SA and AV nodes
- Need to have a Beta blocker or Calcium channel blocker on board to prevent tachyarrhythmias in afib/flutter pts
- Torsades
- Procainimide IV only
What are the drugs for Class Ib?
2
Lidocaine
Mexiletine
- What is lidocaine used for?
- Exerts most of it’s effects on what?
- Particularily useful for what?
- Administered how?
- Toxicity causes? 2
- Used for ventricular arrhythmias (VT, VF)
- ischemic or infarcted tissue of the ventricles
- VT/VF associated with AMI
- IV only
- Toxicity: seizures and respiratory arrest
What is mexiletine?
Oral analog of Lidocaine used for ventricular arrhythmias
What are the Class Ic drugs? 2
Flecainide (Tambocor)
Propafenone (Rhythmol)
- Flecainide (Tambocor) mainly used for what?
2. When can we not use it? 4
- Mainly used for rhythm control in afib/flutter
- –FDA approved to use for ventricular arrhythmias but is not very effective for these and has a high incidence of adverse effects
Cannot use if any hx of structural heart disease
- CAD,
- LVSD,
- valvular disorders,
- LVH
otherwise proarrhythmic
Propafenone (Rhythmol) is used for what?
Cannot be used in what situations?
Used for atrial arrhythmias such as afib/flutter
Cannot be used if hx of structural heart disease
Beta blockers are used for?
4
- Used for suppression of ventricular and supraventricular arrhythmias
- Slow AV nodal conduction and SA nodal rates
- Negative inotropic agents
- Decrease myocardial oxygen consumption
Review of beta blocker SE
8
- Bronchospasm
- Fatigue
- Depression
- Nightmares
- Erectile dysfunction
- Hypotension
- Bradycardia
- Worsening CHF (in some patients…end stage or in acute decompensated state)
What are Class III drugs?
what does it block and what are the drugs 4?
POTASSIUM CHANNEL BLOCKERS
- Amiodarone (Cordarone)
- Dofetilide (Tikosyn)
- Ibutilide (Corvert)
- Sotalol (Betapace)
Class III Antiarrhythmics
work how?
Prolong the action potential
Amiodarone (Cordorone) is used for what? 2
- Rhythm control of atrial fibrillation and flutter
2. Ventricular arrhythmias
Sotalol (Betapace) used for what? 2
Ibutilide (Tikosyn) used for what?
VT and atrial fibrillation
Rhythm control of atrial fibrillation and flutter
Monitor for EKG changes
2
Which drugs should we not use it with?
- May induce ventricular arrhythmias and ectopy
- May change intervals
PR, QRS, QT
Don’t use with other drugs that prolong the QT interval
Why is Amiodarone unique?
How is it administered?
Probably the most widely used medication for rhythm control for atrial fibrillation and VT
Unique in that it has characteristics of all 4 antiarrhythmic drug classes
Given IV for acute treatment
Amiodarone PK/PD
- Bioavialbility?
- Volume of distribution?
- lipophilic or hydrophilic?
- These characteristics may lead to what?
- Poor bioavailability
- Large volume of distribution
- Highly lipophilic
- These characteristics may lead to build up of the drug in various organs
What organs might amiodarone build up in? 8
Amiodarone toxicities can cause?
9
(what is the most life threatening?)
- Lungs,
- thyroid,
- eyes,
- heart,
- liver,
- skin,
- GI tract,
- CNS
- Dermatologic
- Photosensitivity
- Blue-gray skin discoloration
- Neurologic
- Ataxia
- Peripheral neuropathy
- Fatigue
- insomnia
- The pulmonary toxicity acutely can be life threatening, chronically leads to interstitial lung disease
Amiodarone monitoring
What labs should be looked at every 6 months to monitor amiodarone? 3
Baseline and Yearly? 3
- TSH,
- CBC,
- LFTs
- PFTs (DLCO)
- CXR
- Eye Exam
Amiodarone visual complications?
6
- Optic neuritis,
- optic neuropathy,
- corneal and lens opacities,
- halos,
- blurred vision,
- photophobia
SE of amiodarone
- GI disturbance common on higher doses
2. Drug interactions
Amiodarone:
GI disturbance common on higher doses are? 4
Drug interactions?
5
(what are the two to remember?)
- N/V,
- anorexia,
- abd pain,
- constipation
- Substrate of the CYP3A4 isoenzyme
- Significant interactions with digoxin!!!!! and warfarin!!!!
- Potentiates the effects of warfarin
- Can double the serum dose of digoxin
- Interacts with simvastatin (Zocor) so max dose of Zocor is 20 mg
- Sotalol (Betapace)
used for? 2 - Has what kind of properies? (which causes what kind of EKG SE?)
- During initiation of the drug what do we need to do and why?
- Side effects?
- Who should we not use in and why?
- Cleared by what?
- Risk for what?
- VT and afib/flutter
- Has some beta blocking properties and prolongs the QT
- During initiation of the drug: hospitalize for 3 days to monitor
QT interval due to risk for TdP - SE similar to B-blockers: fatigue, dyspnea, bradycardia.
- Negative inotropic effects so usually don’t use in LVSD
- Renal clearance
- Risk for torsades
- Dofetilide (Tikosyn) used for what?
- Can cause what on the EKG?
- Risk of what with increased serum concentrations?
- SE? 2
- Used for afib/flutter
- QT prolongation
- Risk of torsades when increased serum concentrations
- SE include HA and dizziness
Dofetilide (Tikosyn)
Many drug interactions including what?
8
- TMP-SMX,
- macrolide abx,
- verapamil,
- antifungals,
- SSRIs,
- Diltiazem,
- Grapefruit juice,
- caution with metformin
Ibutilide (Corvert) is used for what?
Administered how?
Major adverse effect?
IV only for acute conversion of afib/flutter to sinus rhythm
Major adverse effect is torsades
CLASS IV block what?
Which kind do we use?
CALCIUM CHANNEL BLOCKERS
Nondihyros
Nondihydropyridine calcium channel blockers:
- Decrease automaticity where?
- Decrease conduction where?
- Treatment for? 4
What do we need to remember about this drug???
- Decrease automaticity in the SA and AV node
- Decrease conduction through the AV node
- Used for treatment of
- -supraventricular arrhythmias
- -PSVT,
- -atrial fibrillation,
- -atrial flutter
ONLY WORK ON ATRIA (if you have someone with PVCs you need to give them a beta blocker instead)
Cardiac effects of NDHP CCBs:
- Relaxes what?
- Dont use in which pts and why?
- which is the best?
- What kind of chronotropic effect?
- Vascular relaxation
- Negative intropic effect (don’t use in LVSD)
- Verapamil > Diltiazem
- Negative chronotropic effect
NDHP CCBs should not be used in which pts and why?
Do not use in WPW or an accessory pathway because they can shorten the refractory period of the accessory pathway and increase the ventricular rate and lead to VF
SE of NDHP CCBs:
1. Why do we need to give verapamil slowly?
- Other side effects? 8
- Verapamil IV should be given slowly otherwise can cause severe hypotension
- Bradycardia,
- heart block,
- headache,
- flushing,
- dizziness,
- peripheral edema
- Constipation with verapamil
- Many drug-drug interactions: CYP3A4 isoenzyme
