antiarrhythmic drugs Flashcards
1
Q
What is digoxin? What is digoxin used for?
A
- digitalis glycoside
- antiarrhythmic effect on AV node
- used for ventricular rate control in afib and flutter
- used for its positive inortope effect in CHF
- IT DOESNT convert rhythms to sinus
- doesn’t work well for slowing ventricular rates during exercise
2
Q
MOA of digoxin?
A
- slows the electrical conduction through the AV node
- stimulates the parasympathetic nervous system and increases vagal tone
- slows av conduction and prolongs AV nodal refractory period:
increases PR interval, downward sloping ST seg depression, and shortened QT interval
** wont work in exercise: SNS will override PNS effect of digoxin
3
Q
Dosing of digoxin?
A
- slow onset
- need a loading dose period
- may take a week fo 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 (higher levels in pts with LVSD(CHF) = higher mortality)
4
Q
How can digoxin reach toxic levels in the body?
A
- declining renal fxn: renal excretion
- electrolyte disturbances: hypokalemia, hypomagnesemia, and hypercalcemia can predispose the myocardium to toxic effects of digoxin
- drug interactions: may meds may increase serum digoxin levels: amiodarone, and verapamil
5
Q
Signs and sxs of digoxin toxicity?
A
- heart block
- AV junctional tachycardia
- ventricular arrhythmias
- visual disturbances: blurred vision, yellow/green halos
- dizziness
- weakness
- GI: N/V/D and anorexia
6
Q
What is adenosine? MOA?
A
- used to convert PSVT to SR
- activates K channels by increasing the outward K current
- hyperpolarizes the membrane potential and decreases spontaneous SA node depolarization
- inhibits automaticity and conduction in SA and AV nodes
- half life is only 10 seconds
7
Q
CIs to adenosine?
A
- 2nd or 3rd heart block or sick sinus syndrome in absence of pacemaker
8
Q
MOA and use of atropine?
A
- parapsympathetic drug
- enhances sinus nodal automaticity and AV nodal conduction through direct vagolytic action
- blocks acetylcholine and parasympathetic neuroeffector sites
- used for sx bradycardia!!!!!
- may induce tachycardia
9
Q
Atropine CIs?
A
- angle closure glaucoma
- obstructive uropathy (BPH)
- tachycardia
- bowel obstruction or altered bowel transit time
10
Q
Class 1: sodium channel blockers?
A
- class 1a (intermediate onset/offset) - disopyramide, procainimide, and quinidine
- class 1b (fast onset/offset)- lidocaine, mexiletine, and phenytoin
- class 1c (slow onset/offset): flecainide, propafenone
- subdivided by rate of Na channel dissociation
- variable rates of binding and dissociating from Na channel receptor
11
Q
Class 1a drugs? MOA
A
- proarrhythmic (stay away from these)
- used to tx atrial and ventricular rhythms
- ex: quinidine and disopyramide have anticholinergic effects that can lead to increase automaticity of SA and AV nodes.
- need to have BB or CCB to prevent tachyarrhythmias in afib/flutter pts
- used in torsades
- Procainimide IV only
12
Q
Class 1B drugs? MOA?
A
- lidocaine: used for VT and vF
- exerts most of it’s effects on ischemic or infarcted tissue of the ventricles
- particularly usefuly for VT/VF assoc with AMI
- IV only
- toxicity: seizures and respiratory arrest
- mexiletine: oral analog of lidocaine used for ventricular arrhythmias
13
Q
Class 1c: Flecainide (Tambocor)
A
- mainly used for rhyhthm control in afib/flutter
- FDA approved for vent arrhythmias but isn’t very effective (adverse effects)
- can’t be used if any hx of structural heart disease (CAD, LVSD, valvular disorders, LVH). otherwise proarrhythmic
- not first line in afib/flutter
14
Q
Class 1c: propafenone (rhythmol)
A
- used for atrial arrhythmias such as afib/flutter
- can’t be used if hx of structural heart disease
15
Q
Class II BBs list?
A
- atenolol
- esmolol
- metoprolol
- propranolol
