procainamide in serum/plasma
Indications
- therapeutic drug monitoring, procainamide therapy
Reference interval
- 4-10 ug/mL
Therapeutic procainamide concentrations vary significantly depending on the individual patient. Published information sources say that a range of may indicate effective serum concentration for many patients; however, some individuals are best treated at concentrations outside this range. Concentrations greater than 10 ug/mL are often associated with toxic symptoms.
In normal clinical use N-acetylprocainamide (NAPA) would be analyzed in conjunction with procainamide when evaluating patient specimens. The combined procainamide & NAPA therapeutic range is 10-30 ug/mL. Combined concentrations greater than 30 ug/mL are often associated with toxic symptoms. The physician must determine the appropriate therapeutic range for each patient.
Principle
The PROC pack is used in the DuPont ACA discrete clinical analyzer to quantitatively measure procainamide in serum & plasma. It is an adaptation of Syva's homogeneous enzyme immunoassay technique, EMIT. The reagents used in this methodology are matched lots of procainamide antibody & the procainamide-glucose-6-phosphate dehydrogenase conjugate. The concentration of procainamide determines the amount of procainamide-glucose-6-phosphate dehydrogenase (PROC-G6PD) conjugate that is bound to the procainamide antibody. The unbound conjugate catalyzes the oxidation of glucose-6-phosphate, with the simultaneous reduction of NAD to NADH, more rapidly than does the bound conjugate. The rate of increasing absorbance at 340 nm due to the increase in NADH is related to the concentration of procainamide by means of a calibration curve or a mathematical function.
Clinical significance
Procainamide has been used in the treatment of a wide variety of cardiac arrhythmias, & with comparable therapeutic effects. Some patients, however, will respond to one drug & not to the other. Procainamide is often the preferred drug for the treatment of ventricular premature contractions & ventricular tachycardia. Important exceptions are the ventricular arrhythmias due to digoxin toxicity, in which procainamide may be contraindicated.
Specimen
Patient preparation: No special patient preparation is required.
Collect blood samples by venipuncture following established good laboratory practices. If the sample is obtained through the infusion set, flush the line thoroughly with saline before taking the blood sample. With some exceptions, any anticoagulant may be used to collect plasma for analysis. Serum, as well as plasma, may be used for most assays. If is very important that the physician be informed of the times of sample collection & dose administration; this information should be supplied to the laboratory with each sample & reported with the results of each test. Samples derived from blood should be refrigerated upon collection & stored frozen (-20 degrees Celsius or colder) if not analyzed within 24 hours. Complete mixing of each thawed sample is required before analysis.
More general terms
Additional terms
Component of
References
- ↑ ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 1: Operation, DuPont Company, Wilmington, Delaware, 1984.
- ↑ ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 3B: Chemistry, DuPont Company, Wilmington, Delaware, 1984.
- ↑ Mini Panel of 2 tests: N-acetylprocainamide (NAPA) . Procainamide Laboratory Test Directory ARUP: http://www.aruplab.com/guides/ug/tests/0090151.jsp