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Test ID ETHSX Ethosuximide, Serum

Useful For

Monitoring therapy

 

Determining compliance

 

Assessing toxicity

Method Name

Enzyme-Multiplied Immunoassay Technique (EMIT)

Reporting Name

Ethosuximide, S

Specimen Type

Serum

Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.5 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Forms: If not ordering electronically, complete, print, and send a Neurology Test Request Form-General (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 14 days
  Frozen  28 days
  Ambient  14 days

Clinical Information

Ethosuximide (Zarontin) is used in the treatment of absence (petit mal) seizures, although valproic acid and methsuximide are used more frequently for this condition. Ethosuximide is completely absorbed from the gastrointestinal tract, reaching a peak plasma concentration in 1 to 7 hours.

 

Approximately 10% to 20% of the drug is excreted unchanged in the urine; the remainder is metabolized by hepatic microsomal enzymes. The volume of distribution of ethosuximide is 0.7 L/kg, and its half-life is 40 to 50 hours. Little ethosuximide circulating in the blood is bound to protein.

 

Ethosuximide produces a barbiturate-like toxicity, characterized by central nervous system and respiratory depression, nausea, and vomiting when the blood level is >150 mcg/mL.

Reference Values

Therapeutic: 40-100 mcg/mL

Critical value: >150 mcg/mL

Cautions

No significant cautionary statements

Day(s) Performed

Monday through Sunday; Continuously

Report Available

Same day/1 day

Performing Laboratory

Mayo Medical Laboratories in Rochester

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

80168

NY State Approved

Yes