Anti-arrhythmic Drugs

Question 0

Mexiletine/ mexitil

Answer 0

Class 1b Na channel blocker
Blocks open Na channels- shortens phase 3 repolarization
Used for ventricular arrhythmias, particularly V-tach after MI
May cause drowsiness, confusion, pro-arrhythmia

Question 1

Quinidine/ Quinidex

Answer 1

Class 1a Na channel blocker
Dec inward flow of Na at phase 0= dec automaticity and a lengthened refractory period
Used for A-flutter, A-fib, AV & ventricular arrhythmias
May cause cinchonism- BLURRED VISION, tinnitus, n/v, HA, disorientation, psychotic states
Possible torsade de pointes- ventricular tachycardia

Question 2

Flexainide/ tambocor

Answer 2

Class 1c Na channel blocker
Slows phase 0 depolarization.
Used for supraventricular tachyarrhytmias, Wolff-Parkinson-white syndrome, paroxysmal supraventricular tachycardia(PSVT), and v-tach
Pro-arrhythmic, contraindicated with hx of MI, low TI

Question 3

Atenolol

Answer 3

Class II beta blocker
Blunt sympathetic influence on AV & SA nodes- reduces sympathetic effects on myocardium, diminished phase 4 depolarization
Used for bradycardia, hypotension, dizziness, depression, fatigue, impotency
May cause tachyarrhytmias- a-flutter, a-fib, atrioventricular and ventricular arrhythmias, PSVT, HTN, angina
Dec with a “step down” approach

Question 4

Amiodarone/ cordarone

Answer 4

Class III K channel blocker
Potassium channel blocker, prolongs phase 3. Affect on sympathetic blockade at Na & Ca channels
Used for ventricular arrhythmias usu following MI. Pre tx for pacemaker
May cause dizziness, pulmonary fibrosis, BLUE-GRAY SKIN with sun exposure
High IODINE content- contraindicated in goiter, graves dz, hypothyroid

Question 5

Verapamil/ calan/ isoptin

Answer 5

Class IV Ca channel blocker
Ca channel blocker- slows phase 4 depolarization- slowed AV conduction
Used for A-flutter, A-fib, PSVT, HTN, angina
May cause dizziness, flucng, HA, hypotension

Question 6

Adenosine/ adenocard

Answer 6

Endogenous neucleoside
Prolongs the refractory period, dec automaticity in AV node= heart block with the hope of restarting correctly
Used as initial drug for PSVT
May cause transient hypotension & chest pain
IV use only, duration 15 sec

Question 7

Atropine

Answer 7

Tropane alkaloid
Anticholinergic- competitive inhibitor of the muscarinic ACH receptors- parasympatholytic
Poisoning- Blurred vision, dialated pupils, dry mouth, inc HR, dec secretions, flushed dry warm skin, visual changes, delirium, hallucinations
“Dry as a bone, red as a beet, hot as a hare, blind as a bat, mad as a hatter.”
•The specific antidote for atropine toxicity (or tropane alkaloid toxicity) is physostigmine, a reversible ACH inhibitor.

Used as emergent tx of severe bradycardia with hypotension, also- dialates pupils, tx diarrhea, decrease bronchial & salivary secretions
treatment(antidote) for organophosphate poisoning

Question 8

Organophosphate poisoning

Answer 8

S- salivation
L- lacrimation
U- urination
D- diarrhea
G- gastric distress
E- emesis

Question 9

Digoxin

Answer 9

Cardiac glycoside
Inhibits Na/K ATPase pump- inc inward current of Na followed by greater influx of Ca
Used for CHF- slows ventricular rate in a-fib & flutter by inc sensitivity of AV node to vagal stim, allows increased renal profusion
Low TI
Dose with K sparring diruetic
Antidote- digoxin immune fabs/ digibind
Intoxication:
• Cardiac signs: arrhythmias, including bradycardia, partial or complete heart block.
• GI: nausea, vomiting, anorexia and diarrhea.
• CNS: drowsiness and fatigue.
• Visual disturbances: blurred vision, double vision, flickering dots or flashes of light, halos may appear around objects.

Question 10

Digitoxin

Answer 10

Cardiac glucoside
Same as digoxin but with a longer half life than digoxin= inc risk of toxicity- seldom used
Low TI
Dose with K sparring diruetic

Question 11

Cardiac glycoside intoxication

Answer 11

SSX:
Cardiac- bradycardia, partial or complete heart block
GI- n/v, anorexia, diarrhea
CNS- drowsiness, fatigue
Visual- blurred/double vision, flickering dots, flashes, halos