Ethosuximide, Serum
Use
Monitoring ethosuximide therapy is essential for ensuring compliance and assessing potential toxicity. It is used in the treatment of absence (petit mal) epilepsy in adults and children aged 3 years and older. Monitoring helps to maintain ethosuximide levels within the therapeutic range of 40-100 mcg/mL while avoiding toxic concentrations, which can lead to barbiturate-like toxicity with CNS and respiratory depression, nausea, and vomiting when blood levels exceed 120 mcg/mL. Approximately 10-20% of ethosuximide is excreted unchanged in urine, and the remainder is metabolized by hepatic enzymes.
Special Instructions
Serum gel tubes should be centrifuged within 2 hours of collection, and the serum aliquoted into a plastic vial. If collecting using a red-top tube, ensure serum is similarly processed within this time frame. Testing is to be conducted Monday through Saturday with same day or 1-day turnaround for results availability.
Limitations
The test has not been cleared or approved by the US Food and Drug Administration, though it is performed consistently with CLIA requirements. Interferences by endogenous serum G6PD are mitigated by the assay's use of a bacterial enzyme, ensuring accurate measurement irrespective of native enzyme levels.
New York Approved
Methodology
Immunoassay (EMIT)
Biomarkers
LOINC Codes
- 3616-0
- 3616-0
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
0.5 mL
Minimum Volume
0.25 mL
Container
Serum gel, Red top (Plastic vial for submission)
Collection Instructions
Serum gel tubes should be centrifuged within 2 hours of collection. Red-top tubes should be centrifuged and the serum aliquoted into a plastic vial within 2 hours of collection.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 28 days |