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Valproic Acid
Test CodeAlias/See Also
CPT Codes
80164
Preferred Specimen
Serum (gold top) tube
Minimum Volume
Other Acceptable Specimens
Instructions
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.
Transport Container
Serum (gold top) tube or Lithium Heparin Plasma (green top) tube
Transport Temperature
Specimen Stability
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Methodology
Photometric
Setup Schedule
Daily upon receipt
Report Available
Limitations
Reference Range
Therapeutic Range: 50 - 120 ug/mL
Clinical Significance
Valproic acid is used as sole or adjunctive therapy in the treatment of simple and complex absence seizures, and adjunctively in patients with multiple seizure types, which include absence seizures. High concentrations of valproic acid may lead to central nervous system depression, tremor, and thrombocytopenia. Very high concentrations of valproic acid may also increase the risk of developing fatal hepatotoxicity, stupor, coma, or cerebral edema. Valproic acid is extensively etabolized by the liver. Other coadministered drugs, including other antiepileptics, may induce or inhibit the drug metabolizing enzymes of the liver. When these drugs are added or removed from the therapeutic regimen of a patient, the clearance and concentration of valproic acid may be altered, requiring dosage adjustment. Serum or plasma valproic acid measurements are used in the diagnosis and treatment of valproic acid overdose and in monitoring levels of valproic acid to ensure appropriate therapy.