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Test Code PA Procainamide and N-Acetylprocainamide, Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.


Useful For

Monitoring therapy with procainamide

 

Assessing compliance

 

Evaluating procainamide toxicity

Method Name

Homogeneous Enzyme Immunoassay

Reporting Name

Procainamide and NAPA, S

Specimen Type

Serum

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 14 days
  Refrigerated  7 days
  Ambient  24 hours

Reject Due To

Gross hemolysis Reject

Clinical Information

Procainamide (PA) is indicated in the treatment of life-threatening ventricular arrhythmias.

 

PA is metabolized to an active metabolite, N-acetylprocainamide (NAPA), with metabolism controlled by genetically determined enzymes. In patients with normal kidney function, fast metabolizers will have a PA:NAPA ratio less than 1 at 3 hours after the dose is administered. Slow acetylators (PA:NAPA ratio >2 after 3 hours) are more likely to present with systemic lupus erythematosus-like symptoms and may test positive for antinuclear antibodies.

 

Patients who have prolonged exposure to procainamide levels above 12.0 mcg/mL or a NAPA concentration of 40.0 mcg/mL or higher are very likely to exhibit symptoms of toxicity, which are characterized by hypotension, ventricular fibrillation, widened QRS complex (intraventricular conduction delay), junctional tachycardia, oliguria, confusion, nausea, and vomiting.

 

Kidney disease, liver disease, cardiac failure, and states of low cardiac output reduce the metabolism and clearance of PA and NAPA.

 

Coadministration of histamine H2 receptor antagonists, such as cimetidine and ranitidine reduce renal clearance of PA and NAPA resulting in higher plasma concentrations of each.

Reference Values

Procainamide

Therapeutic: 4.0-10.0 mcg/mL

Critical value: >12.0 mcg/mL

 

N-acetylprocainamide

Therapeutic: 12.0-18.0 mcg/mL

Critical value: ≥40.0 mcg/mL

Interpretation

Administration of a dose of 50 mg/kg will usually yield the optimal trough concentration in the range of 4.0 to 10.0 mcg/mL for procainamide and 12.0 to 18.0 mcg/mL for N-acetylprocainamide.

Cautions

No significant cautionary statements

Day(s) Performed

Monday through Saturday

Report Available

Same day/1 to 2 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80192

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PA Procainamide and NAPA, S 3983-4

 

Result ID Test Result Name Result LOINC Value
8683 Procainamide, S 3982-6
2461 N-acetylprocainamide, S 3834-9
2462 Procainamide + NAPA 3983-4

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.