Pharm #7 - Anti-Arrhythmics Flashcards
Procainimide:
MOA & effect
CLASS 1A drug
Block Na & K channels
- slows upstroke of AP and conduction
- PROLONGS QRS
- direct depressant actions on SA/AV nodes
(use/state dependent)
Procainimide
- clinical application
atrial and ventricular arrhythmias
2nd choice for ventricular arrhythmias after acute MI ((after lidocaine and amiodarone) )
Adverse effects of Procainimide
Why?
Adverse effects/toxicity:
Ganglion blocking properties,
risk of hypotension
Anti-cholinergic effects
Induction of torsade de pointes arrhythmia (NAPA) !!
Long term: Lupus erythematosus syndrome (arthritis, pleuritis…)
in 30% of all patients
adverse effect of tornadoes de points due to metabolite NAPA !
- eliminated renally (need to dose adjust)
Quinidine:
MOA
Adverse Effects
Actions similar to procainamide (Na channel blocker)
Indications: Same as procainamide
Rarely used because of cardiac and extra-cardiac
adverse effects:
- stronger anticholineric
- cinchonism: HA, dizziness, tinnitus
Ganglion blocking properties, risk of hypotension
(» procainamide)
Anti-cholinergic effects, increases sinus rate and AV conduction,
may require co-administration of drugs that slow AV conduction
Induction of ventricular fibrillation and torsade de pointes !!
Disopyramide
MOA
What does it need to be coadministered with?
similar to procainamide
Anticholinergic effects»_space; than procainamide & quinidine
- increase sinus rate and AV conduction and requires co-administration of drugs that slow AV conduction
Negative inotropic effects may induce HF
- most exctra cardiac effects result from atropine like actions
Disopyramide
Approved for?
Approved only for ventricular arrhythmias
not drug of 1st or 2nd choice
What are the three Class1A drugs?
- Procainamide
- Quinidine
- Disopyramide
MOA of Class 1B drugs
Which drugs fall into this class (2)
MOA: fast kinetics, reduction of AP potential duration
- lidocaine
- mexiletine
Lidocaine
MOA
Effect
Na channel blockade
(use/state dependent drug action)
effect: rapid kinetics at normal resting potential:
No effect on conduction,
recovery from block between action potential
Selective depressing of conduction in depolarized (ischemic) cells
Lidocaine
clinical use
DOC?
highly effective for ventricular arrhythmias after MI
DOC: tx of Ventricular tachycardia and fibrillation after cardioversion in setting of ischemic/infarction
PROPHYLACTIC TX not recommended
Lidocaine
PK: how is it metabolized?
Side effect?
EXTENSIVE first pass metabolism by liver
(2 hr half life)
- least cardiotoxic drug!
Neurologic side effects due to local anesthetic properties (paresthesia, tremors, nausea, lightheadedness, hearing disturbances, slurred speech, convulsions)
Large doses may induce hypotension probably through effects
on myocardial contractility
Mexiletine
MOA
Class
Unique off label use?
Class 1 B
(Class I B: fast kinetics, APD decreases)
- Na channel blockade
orally active lidocaine analogue
Actions/adverse effects similar to lidocaine
Off label use: CHRONIC PAIN (diabetic neuropathy, nerve injury)
Which drug is IV only, mexiletine or lidocaine?
LIDOCAINE!
Mexilitine is oral (used off label for chronic pain associated with diabetic neuropathy)
CLass 1 C drugs (2)
MOA
Flecainamide
Propafenone
- slow kinetics, NO EFFECT ON APD
Flecainamide
MOA
effect
Na and K channel block
no effects on APD even tho K channel blocked
NO ANTICHOLINERGIC EFFECTS!
What are class 1 a effects on
- kinetics
- APD
Class 1B?
Class 1 C?
- intermediate kinetics
increase APD - Fast kinetics, decrease APD
- Slow kinetics, no effect on APD
What drugs are in the class1A antiarrhythmics? (3)
Drugs: Procainamide, Quinidine, Disopyramide
Clinical use for Class 1C drugs (1)
- state the 2 drugs
CLinical: Supraventricular arrhythmias in patients with otherwise normal hearts
- flecainamide
- propafenone
PK for flecainamide (elimination)
half life?
Well absorbed, half-life 20 hrs, elimination: liver and kidney
flecainamide (class 1c)
adverse effects/ contraindications (3)
increases mortality in patients with ventricular tachyarrhythmias , MI, and ventricular ectopy (contraindication!)