Class Ia Antiarrhythmic Agents

Question 1

Quinidine Adverse Effects

Answer 1

“cinchonism” (CNS and GI symptoms, tinnitus),
strong vagolytic and anticholinergic properties

Question 2

Quinidine PK/DI

Answer 2

PK: Half-life 5–9 hr
Potent inhibitor of CYP2D6 (Digoxin); substrate and
inhibitor of CYP3A4 (Warfarin)

Question 3

Quinidine (Quinidex,
Quinaglute) Dosing

Answer 3

AF and VT maintenance:
Sulfate: 200–400 mg PO every 6 hr
Gluconate (CR): 324 mg PO every 8–12 hr

Question 4

Quinidine Dose Adjustment

Answer 4

Decrease dose by 25% if CrCl < 10 mL/min

Question 5

Procainamide Contraindication

Answer 5

LVEF < 40%

Question 6

Procainamide Elimination

Answer 6

Active metabolite NAPA (class III effects) may accumulate in renal dysfunction (reduce in renal and liver dysfunction)

Question 7

Procainamide (Pronestyl) Dosing

Answer 7

AF conversion: 1 g IV for 30 min; then 2 mg/min
VT conversion: 20 mg/min IV until 17 mg/kg, arrhythmia ceases, hypotension, or QRS widens > 50%
VT maintenance: 1–4 mg/min

Question 8

Disopyramide Contraindications

Answer 8

potent negative inotropic effect- Cardiogenic shock, congenital long QT syndrome, second- or third-degree AVB,
glaucoma

Question 9

Disopyramide PK/DI

Answer 9

PK: Half-life 4–8 hr
Substrate of CYP2D6
DI: May enhance the effect of β-blockers

Question 10

Disopyramide (Norpace) Dosing

Answer 10

AF conversion: IR 200 mg (if < 50 kg) or 300 mg
(if > 50 kg) PO every 6 hr
AF maintenance: 400–800 mg/day in divided doses IR every 6 hr or CR every 12 hr

Question 11

Disopyramide Dose Adjustments

Answer 11

If < 50 kg, moderate renal dysfunction (CrCl > 40 mL/ min) or hepatic dysfunction, max 400 mg/day
If severe renal dysfunction (IR only; avoid CR)
CrCl 30–40 mL/min, 100 mg every 8 hr
CrCl 15–30 mL/min, 100 mg every 12 hr
CrCl < 15 mL/min, 100 mg every 24 hr

Question 12

Class Ia Adverse Effect

Answer 12

Tdp

Question 13

Class Ia Caution

Answer 13

Avoid in heart failure and acute MI