Specimen Requirements

Special Notes: Pharmacokinetic factors including dosage form, mode of administration and biological variation can influence the appropriate time of sample collection following administration of valproic acid.

Valproic acid monitoring is most appropriate when the blood sample is drawn after steady-state conditions have been reached (after 4–5 half-lives on an unchanged dose regimen).

For patients receiving valproic acid orally the blood sample should be drawn immediately before the next dose because of its short half-life.

Valproic acid samples should be monitored at a consistent time of day because concentration is affected by circadian rhythm.

Specimen Type: Serum

Collection Container/Tube:

Preferred: Plain, red-top tube (SST gel unacceptable)

Specimen Volume: 2 mL

Pediatric (minimum) volume: 0.5 mL in a red top MICROTAINER tube