Procainamide, Serum or Plasma

Casandra

Casandra Test Code LC23928Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 007252CPT Code 80192

Procainamide, Serum or Plasma

Also known as: Pronestyl®

Clinical Use

Order Test

Use

The test is used to monitor the levels of procainamide and its active metabolite N-acetyl procainamide (NAPA) in patients' blood. Procainamide is used in the treatment of various cardiac arrhythmias. Monitoring is essential as the drug exhibits significant interindividual variability in metabolism, especially influenced by genetic factors. Impaired renal function can significantly alter drug disposition, particularly for NAPA, and prolonged half-life can be observed in geriatric patients.

Special Instructions

Patients should note that the optimal plasma sampling time after oral dosage is one to two hours and after I.V. administration, it is 30 minutes. The drug is rapidly absorbed with peak blood levels generally occurring within an hour of administration. It is crucial not to use a gel-barrier tube for collection, as it may significantly affect drug level measurement due to slow absorption by the gel.

Limitations

The rate of metabolism for procainamide is genetically determined, differentiating patients into slow and fast acetylator types. As such, the test cannot account for all variations due to genetic differences. Furthermore, patients with severe renal dysfunction may experience a prolonged and highly variable half-life of the drug, which the test cannot fully account for. Additionally, the use of gel-barrier tubes can result in incorrect measurement due to absorption, which represents another limitation of the testing process.

Test Details

Methodology

Immunoassay

Biomarkers

N-acetylprocainamide (NAPA)

Analyte

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Procainamide

Analyte

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

88699-4

Result Codes

3982-6
3834-9
3983-4

Result Turnaround Time

1 day

Specimen

Serum

Volume

1 mL

Minimum Volume

0.3 mL

Container

Red-top tube or green-top (heparin) tube. Do not use a gel-barrier tube.

Collection Instructions

Transfer separated serum or plasma to a plastic transport tube. Oral treatment: peak: 75 minutes after dose; trough: immediately before next dose. I.V. treatment: immediately after loading dose; 2, 6, 12, and 24 hours after starting I.V. maintenance.