Mar 24, 2015




Clinical Hub,Tools & Resources,UWHC Lab Test Directory,Toxicology


Ethosuximide (XETHO) Toxicology Lab Test

Name: Ethosuximide

Test Name: Ethosuximide

Health Link Test Code: XETHO

LIS Test Code: ESUX

CPT Code(s): 80168

Methodology: Gas Chromatography

Clinical Information:


Days Performed: Daily, dayshift.

In-Lab Turnaround Time: 1 day.

Specimen: Blood

Collection Container: Red top

Collection Instructions:

Collect specimen for trough level prior to next dose.

Collection Volume: 3 mL

Pediatric Collection Volume: 1 mL

Stability Ambient:

12 hours

Stability Refridgerated:

2 days

Stability Frozen:

1 year

Sample Analyzed: Serum

Testing Volume: 1 mL

Pediatric Testing Volume: 0.4 mL

Specimen Processing:

Centrifuge. Transfer cell-free serum to plastic vial. Refrigerate.

Specimen Transport:

Transport specimen to laboratory. Transport with coolant pack if coming from clinic location.

Unacceptable Criteria:

Specimens collected in red cap with yellow ring (SST) tubes are not acceptable.


Generally effective therapeutic concentration:  
18 years and up:   40.0-100.0 mcg/mL


Interpretation Type: Interpretive Guidelines

Critical Calls: yes

Additional Information:

Result of "BELOW DETECTION" indicates that the result is below the method detection limit of 1 mcg/mL. The half-life is 40-60 hours in adults, 30-50 hours in children. Ethosuximide has been reported to cause elevation of serum phenytoin concentrations when two drugs are given concurrently. Concurrent therapy with valproic acid has been reported to cause elevations in ethosuximide concentrations.


This test was developed and its performance characteristics determined by the UWHC Clinical Laboratories.  This test meets the standards for clinical testing.  This test should not be regarded as investigational or for research use.  The US Food and Drug Administration (FDA) has not approved or cleared this test; however, the FDA has determined that such clearance or approval is not necessary.