Sodium channel blockers

Question 1

Class 1a Na blockers

Answer 1

Quinidine, procainamide, disopyramide

2nd in blocking the AP
1st in increasing the ERP

increased AP duration
increased Refractory period (due to non specificity (towards K channels))
increased QT

Question 2

Class 1b Na blockers

Answer 2

Lidocaine, mexiletine

3rd in blocking the AP
3rd in increased the ERP (it decreases it)

Increased AP duration
Decreased refractory period

1B is Best most MI

Question 3

Class 1c Na blockers

Answer 3

Flecainide, Propafenone

1st in blocking the AP
2nd in increasing the ERP

increases AP duration
minimal effect on ERP

Question 4

procainamide

Answer 4

Class Ia antiarrythmetic (2nd in blocking the AP
1st in increasing the ERP)

SE: induction of torsades de pointes, long term use gives SLE like Sx

Question 5

Quinidine

Answer 5

Class Ia antiarrythmetic (2nd in blocking the AP
1st in increasing the ERP)

SE: torsades

Question 6

Disopyramide

Answer 6

Class Ia antiarrythmetic (2nd in blocking the AP
1st in increasing the ERP)

Pearls: loading dose NOT recommended because of risk of precipitating heart failure

Question 7

Lidocaine (as a heart drug)

Answer 7

Class Ib antiarrhythmic (3rd in blocking the AP
3rd in increased the ERP (it decreases it))

pearls: prophylactic use may actually increase total mortality

Question 8

Mexiletine

Answer 8

Class Ib antiarrhythmic (3rd in blocking the AP
3rd in increased the ERP (it decreases it))

Pearls: Significant efficacy in relieving chronic pain, especially due to diabetic neuropathy and nerve injury (off-label use.)

Question 9

Flecainide

Answer 9

(Class IC Antiarrhythmic)

pearls: slow unblocking kinetics
contraindicated in MI

Question 10

Propafenone

Answer 10

(Class IC Antiarrhythmic)

pearls: Weak β-blocking activity.