Procainamide

 Procainamide:

(Lexicomp, 21^st ed. 2014-2015)

 

SVT:

(May use for stable, monomorphic VT and pre-excited A fib).

Newborn:

IV-Loading dose 5-10 mg over 60 min.

Infusion: 20 – 80 mcg/kg/min.

(Lower dose for preterm and renal impairment).

Infants/Children/Adults:

Loading dose 10-2 mg/kg over 30-60 min.

Infusion: 20-80 mcg/kg/min.

 

Monitoring:

EKG (PR interval, QTc prolongations), BP, CBC/diff.

Drug level: 6-12 hrs. after starting infusion.

Therapeutic range:

Procainamide level 4-10 mcg/ml. (> 10-12 mcg/ml is toxic)

Proc + NAPA level = 10-30 mcg/ml.

Side effects:

- PR, QTc prolongation, Paradoxical increase in ventricular rate in Afib.

- Agranulocytosis

- ANA positive

- Others.

Flecainide Dose (Lexicomp, accessed on 3/4/2026)

Newborn:

Initial: 2 mg/kg/day in 2 divided doses.

Usual effective dose: 3.35 ± 1.3 mg/kg/day.

 

Children:

Initial: 1-3 mg/kg/day (or) 50 – 100 mg/m2/day in 3 divided doses.

Max: 8 mg/kg/day (or) 200 mg/m2/day.

Usual effective dose: 4 mg/kg/day (or) 140 mg/m2/day.

 

Adults:

Initial: 50 mg q12 or 100 mg qd.

Increase dose Q4 days, Max. 300 mg/day for SVT & 400 mg/day for VT.

Pill-in-pocket for A fib: 200 mg (< 70 kg) & 300 mg (> 70 kg). Patient should be on AV nodal blocking agent (Beta-blocker or Calcium-channel blocker) while on this plan. Inpatient trial should be done prior to discharge to check its efficacy.

 

Monitor: 

EKG, Serum trough level. LFT, CBC/diff.

Serum trough level – Check 3 days after starting or changing medication.

Therapeutic level: 0.2 – 1.0 mcg/ml.

In children, response is noted at 0.2 – 0.5 mcg/ml range.

Side effects:

- PR prolongation, QRS widening, paradoxical increase in ventricular rate in A fib.

- Leukopenia, thrombocytopenia

- LFT

- Paraesthesia, blurred vision

- Urticaria

Basel algorithm - To differentiate VT vs. SVT

 

WPW syndrome - Natural History

From James Perry & Arthur Garson Jr. JACC 1990;16:1215-20.

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EKG: Intermittent WPW

Intermittently manifest accessory pathway

Note: Two beats in this rhythm strip have normal PR interval without Delta wave.

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SVT from Holter - Onset and Termination

An ectopy initiates the re-entry circuit.

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Narrow Complex Tachycardia - Atrial Flutter

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Narrow complex tachycardia - Re-entry type

2 yr old, 10 kg. Unbalanced AV septal defect. s/p Takedown of Glenn Operation. Postop. day 5.
Sequence of events during management of tachyarrhythmia:

On Epinephrine, Dobutamine and Milrinone infusions, Digoxin maintenance dose.
Abrupt increase in heart rate from 111/min to 165/min.
Initial diagnosis of SVT. Adenosine (1 mg) administration reveals multipe P waves.
Atrial Flutter is treated with synchronized DC cardioversion (5 Joules).

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Narrow Complex Tachycardia/SVT - 3 types of responses to Adenosine

Response 1 - Adenosine terminates SVT to sinus rhythm
Response 2 - Adenosine terminates SVT to sinus rhythm; but, SVT returns
Response 3 - Adenosine decreases ventricular response, enabling the correct diagnosis of Atrial Flutter (This narrow complex tachycardia was not SVT)

Thus, if Adenosine does not treat it. It helps to uncover the correct diagnosis! It is important to record EKG strip during Adenosine administration so that the type of response can be carefully analyzed and documented.