Antiarrhythmics 2 Flashcards
General MOA of antiarrhythmic drugs:
Alter cardiac rhythm by altering what 4 things?
- Maximum diastolic potential of pacemaker cells (the most negative transmembrane potential achieved by a cardiac cell)
- The rate of phase 4 depolarization
- The threshold potential
- The action potential duration
Which group of antiarrhythmic drugs (AADs) alters cardiac rhythm by altering the threshold potential?
Na and Ca channel blockers
Which group of antiarrhythmic drugs (AADs) alters cardiac rhythm by altering the action potential duration?
K channel blockers
What are the 4 classes of AADs?
Class I- Na channel blockers (procainamide, lidocaine, flecanide)
Class II- Beta adrenergic receptor antagonists (Propanolol)
Class III- K channel blockers (amiodarone)
Class IV- Ca channel blockers (verapamil, diltiazem)
miscellaneous- Adenosine, Mag, Potassium
All class 1 drugs reduce which currents in both phase ___ and phase ___
Sodium currents
Phase 0 and 4
In addition to reducing both phase 0 and phase 4 sodium currents, what do Group 1A drugs also reduce? (2 things)
What is the result of this?
- reduce phase 3 potassium current
- prolong the action potential duration
Result= significant prolongation of the effective refractory period
•Group 1B and group 1C drugs have different (or no) effects on______ current and thus shorten or have no effect on the ____ duration.
Potassium current
Action potential duration
All group 1 drugs prolong the_____ by slowing recovery of sodium channels from inactivation.
ERP (effective refractory period)
What is the MOA of Procainamide (class 1A)
INa (primary) and IKr (secondary) blockade
Which drug has the following 3 effects?
- **Slows conduction velocity and pacemaker rate
- prolongs action potential duration
- direct depressant effects on sinoatrial (SA) and atrioventricular (AV) nodes
Procainamide (Group 1A)
Which med has the following clinical applications?
- **Most atrial and ventricular arrhythmias
- second choice for most sustained ventricular arrhythmias associated with acute MI
Procainamide (class 1A)
Pharmacokinetics of which drug?
Oral, IV, IM
• eliminated by hepatic metabolism and renal elimination
Procainamide (class 1A)
What could happen if you prescribe Procainamide (Class 1A) to a patient with renal failure?
**Torsades de Pointes in patients with renal failure
What are the 2 toxicities of procainamide (Class 1A)?
- **Hypotension
- **long-term therapy produces reversible lupus-related symptoms
MOA of which drug?
- Highly selective INa block
- **minimal effect in normal tissue
- no effect on IK
Lidocaine
What are the 2 clinical applications of Lidocaine (class 1B)
- **Ventricular arrhythmias post-MI
- Digitalis induced arrhythmias
pharmacokinetics of which drug?
IV and IM
Duration: 1-2
Lidocaine (class 1B)
in what patients should you reduce the dose of Lidocaine?
patients with heart failure or liver disease
Toxicity of which drug?
**Central nervous system (CNS) sedation or excitation
Lidocaine (Class 1B)
*this is a lipophilic drug so it can cross the blood brain barrier)
What is the MOA of Flecainide (class 1C)?
Sodium channel blockade
The following is the effects of which drug?
- Dissociates from channel with slow kinetics
- no change in action potential duration
Flecainide (class 1C)
The following are clinical applications of which med?
- Supraventricular arrhythmias in patients with normal heart
- do not use in ischemic conditions (post-myocardial infarction)
Flecainide (class 1C)