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Ethosuximide Level

Zarontin

Test Codes

EPIC: LAB5389, Beaker: ETHOS, Warde: ETHSX

Department

Send Outs

Specimen Collection Criteria

Collect: One plain Red-top tube. (Minimum Whole Blood: 2.0 mL)

Acceptable: Plasma, Lavendar EDTA, Green Sodium or Lithium Heparin.

Do not use Serum Separator Tubes.
Time of Collection: Trough, just prior to the next dose.
Record the exact time of specimen collection on the tube or in the computer system.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes. Centrifuge, separate serum from cells and transfer serum into a plastic transport tube. Refrigerate (2-8°C or 36-46°F) prior to transport. (Minimum: 2.0 mL blood)

Preparation for Courier Transport

Transport: 1.0 mL serum, refrigerated (2-8°C or 36-46°F). (Minimum: 0.2 mL)

Rejection Criteria

• Serum Separator (SST) tubes.
• Severely lipemic or hemolyzed specimens.

In-Lab Processing

Let specimens clot 30-60 minutes. Centrifuge, separate serum from cells and transfer serum into a plastic transport tube. Refrigerate (2-8°C or 36-46°F) prior to transport. (Minimum: 0.2 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 48 hours
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 14 months

Laboratory

Sent to Warde Medical Laboratory, Ann Arbor, MI.

Performed

Monday – Friday.
Results available 1-3 days.

Reference Range

Therapeutic Range: 40-100 mcg/mL.
Critical: Greater than 200 mcg/mL.

Test Methodology

High Performance Liquid Chromatography.

Interpretation

Ethosuximide has an elimination half-life of from 1 to 3 days. Up to two weeks may be required to achieve steady-state. Drugs that induce oxidative metabolism will typically increase Ethosuximide clearance.

Clinical Utility

This assay is used to monitor the therapeutic drug concentration and evaluate the toxicity of ethosuximide. Ethosuximide is an anticonvulsant that is the drug of choice in the treatment of absence (petit mal) epilepsy.

CPT Codes

80168

Contacts

Last Updated

10/10/2023