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HelpTest 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, SSpecimen Type
SerumSpecimen 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
Method Description
These assays are based on a homogeneous enzyme immunoassay technique. The assay is a competition assay between the drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PD) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change that is measured spectrophotometrically. Endogenous serum G6PD does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package inserts: Procainamide and N-acetylprocainamide. Roche Diagnostics; 08/2015)
Day(s) Performed
Monday through Saturday
Report Available
Same day/1 to 2 daysPerforming 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 |