Test Name: Valproate
Health Link Test Code: DEP
LIS Test Code: VATE
CPT Code(s): 80164
Methodology: Particle Enhanced Turbidometric Inhibition Immunoassay (PETINIA)
Days Performed: Daily, 24 hours.
In-Lab Turnaround Time: 4 hours.
Stat In-Lab Turnaround Time: 1 hour.
Collection Container: Red top
Collect specimen for trough level prior to next dose.
Collection Volume: 2 mL
Pediatric Collection Volume: 0.4 mL
Sample Analyzed: Serum
Testing Volume: 1 mL
Pediatric Testing Volume: 0.2 mL
Centrifuge. Transfer cell-free serum to plastic vial. Refrigerate.
Transport specimen to the laboratory. Transport with coolant pack if coming from clinic location.
Specimens collected in red cap with yellow ring (SST) tubes are not acceptable.
Generally effective therapeutic concentration: 50.0-100.0 ug/mL
There is an increased incidence of side effects seen at concentration greater than 130.0 ug/mL.
Critical Calls: yes
Result of "BELOW" indicates that the concentration is below the method detection limit of 12.5 ug/mL. The half-life of valproate is approximately 8-12 hours. Peak concentrations occur 0.5-2 hours after administration of capsules or syrup; 3-8 hours after enteric coated tablets. The drug is primarily metabolized in the liver and is excreted as the glucuronide conjugate in the urine. Valproate is generally considered to be an enzyme inhibitor. Concurrent administration may result in increased carbamazepine-10,11-epoxide, ethosuximide, phenobarbital, and unbound phenytoin concentrations. Concurrent administration with enzyme inducing drugs may cause marked decrease in valproate half-life and plasma concentrations.