Valproic Acid (Total+Free)
Use
Valproate (valproic acid; divalproex sodium, a compound containing sodium valproate and valproic acid) controls absence, myoclonic, and tonic-clonic seizures in generalized, idiopathic, and symptomatic epilepsy. It is most useful in typical absence seizures. Valproate is as effective as ethosuximide in patients with absence seizures alone and is variably effective in atypical absence seizures. Although some clinicians prefer valporate for absence seizure, the American Academy of Pediatrics recommended that it be reserved for use when therapeutic failure or intolerance to ethosuximide occurs, because valproate causes rare but potentially fatal hepatotoxicity. Many neurologists consider valproate the drug of choice for patients with both absence and other generalized seizure types, including tonic-clonic convulsions. Its efficacy is about the same as in patients with the latter type alone. Valproate is an alternative drug in the treatment of complex partial seizures but may be considered for initial therapy in patients with partial and secondarily generalized seizures.
Special Instructions
Serum concentration monitoring is recommended to guide therapy, particularly monitoring of trough concentrations. Uniform timing in sampling is important due to daily fluctuations in free fraction and clearance, potentially influenced by meals, and displacement by free fatty acids or circadian influences.
Limitations
Hepatotoxicity may be fatal and is idiosyncratic. Routine monitoring of liver enzymes does not prevent this risk. Valproate-induced cytopenias should be monitored via complete blood counts during therapy. Encephalopathy with hyperammonemia may occur without liver dysfunction. Pregnant women in their first month are at risk of neural tube defects.
Methodology
Immunoassay
Biomarkers
LOINC Codes
- 57775-9
- 4086-5
- 4087-3
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2.7 mL
Minimum Volume
1.4 mL
Container
Red-stopper tube; transfer separated serum to a plastic transport tube. Do not use a serum separator tube
Collection Instructions
Oral: peak: 1 to 4 hours after dose (influenced by meals); trough: immediately prior to next dose
Storage Instructions
Room temperature
Causes for Rejection
Gel tube; hemolysis; lipemia
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |
