Anti-arryhthmic Drugs

Question 1

Class I (Na+ channel blockers)

Answer 1

Question 2

Class IA

Answer 2

Quinidine
Procainamide
Disopyramide

MOA: Block phase 0 (slows) - Na+ and Block phase 3 (prolongs) - K+

SIDE EFFECTS: Hardly ever used because of side effects, proarrhythmic (Induce prolonged QT), high cardiac and non-cardiac risk

Question 3

Class IB

Answer 3

Lidocaine
Mexiletine (oral)

MOA: Shorten the duration of the action potential, mild

INDICATIONS: Only work for ventricular arrythmias (ventricular tissue)

SIDE EFFECTS: CNS effects (Lidocaine) in high doses; GI side effects (Mexiletine)

CONTRAINDICATIONS: Liver disease, heart disease where accumulation occurs

Question 4

Class IC

Answer 4

• *Flecainide**
• *Propafenone** (slight beta blocker)

INDICATIONS: atrial fibrillation with structually normal heart

CONTRAINDICATIONS: CAD/HF; people more likely to die with CAD

SIDE EFFECTS: Bronchospams with propafenone because of beta blockage, usually well tolerated

Question 5

Class II

Answer 5

Beta Blockers (-olols)

MOA: Prolong phase 4 (funny current) and prolongs phase 3 (repolarization); slows heart rate down
Prevent ventricular arrythmias so they are useful after a heart attack

INDICATIONS: Rate control, afib and aflutter, SVT’s

SIDE EFFECTS: fatigue, bronchospasm, hypotension, depression, etc.

Question 6

Class III

Answer 6

Dronadarone (GI side effects)
Amiodarone
Sotalol (K+ and B blocker)
Ibutilide
Dofetilide (have to admitted to use)

MOA: Slows repolarization (K+ channels) and extends phase 3, on ecg you will see a longer QT

SIDE EFFECTS: Torsades de pointes, prolonged QT

Question 7

Amiodarone

Answer 7

MOA: Highly lipophillic and large volume of distrbution (gets everywhere), requires a huge loading dose to get to steady state. Half life is like two months, can be a year until its gone.
Inhibitor and metabolizer of CYP enzymes

SIDE EFFECTS: High drug interactions, amiodorone IV can cause hypotension (diluent causes hypotension), bradycardia, AV block, pulmonary disorder, thyroid disorders (hypo/hyper), more sensitive to halogenated anesthetics, GI side effects, skin discoloration (blueish grey tint), sleep disturbances, corneal disturbances

MONITORING: a lot because of the side effects

CONTRAINDICATIONS: Iodine hypersensitivity, prior shock, sinus bradycardia

BLACK BOX WARNING**: Pulmonary toxicity, liver injury, can cause heart block and sinus

Question 8

Class IV

Answer 8

INDICATIONS: SVT, afib, aflutter to lower heart rate

SIDE EFFECTS: Hypotension, bradycardia, etc.

Question 9

Digoxin

Answer 9

MOA: Prolongs phase 4, increases parasympathetic tone, increased dose can get positive inotropic effects

INDICATIONS: Only good for people who are stationary, used in combination with calcium channel blocker or beta blocker. Useful in heart failure or afib

SIDE EFFECTS: Increased dose can cause proarryhthmic effect, narrow therapeutic window, GI upset, halovision (color perception), bradycardia, AV block, ventricular tachycardia and can be lethal

Question 10

Adenosine

Answer 10

MOA: Natural substance in our body that allows potasium to escape from inside the cell, opens the channels and the concentration gradient makes the inside of the cell more negative (hyperpolarizes). Slows the heart rate in AV node causing AV nodal block

INDICATIONS: SVT, arryhthmias originating in the AV node, good therapeutically and diagnostically

Half life is 1-6 seconds it is quick off so there is not a lot of risk with it