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Beaumont Laboratory

Zonisamide Level

Zonegran, Antrim #19574, EPIC: LAB5433, SOFT: ZONIS

Specimen Collection Criteria

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

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/Drawsite Specimen Preparation

Let specimens clot 30-60 minutes. Refrigerate (2-8°C or 36-46°F) the collection tube within two hours of collection. (Min: 2.0 mL blood)

Preparation for Courier Transport

Transport: Collection tube, refrigerated (2-8°C or 36-46°F). (Min: 2.0 mL blood)

Rejection Criteria

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


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 8 hours
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 2 months


Royal Oak Toxicology Laboratory.


Monday, Wednesday, Friday.
Results available the same day as testing performed (1-3 days).

Reference Range

Therapeutic Range: 10-40 mcg/mL.
Critical Value: 80 mcg/mL.

Test Methodology

Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS). 

This test was developed and its performance characteristics determined by Beaumont Health. It has not been cleared or approved by the FDA. The Laboratory is regulated under CLIA as qualified to perform high-complexity testing. This test is used for clinical purposes and should not be regarded as investigational or for research.


Zonisamide is distributed extensively to red blood cells. Hemolysis will falsely elevate serum measurements. Zonisamide has an extended elimination half-life (2-3 days) and time to steady-state may be two weeks. Zonisamide is eliminated by renal and metabolic means. A decline in renal function will increase Zonisamide steady-state concentrations. Concurrent drugs that induce hepatic metabolism (Phenytoin, Phenobarbital, Carbamazepine) will typically decrease steady-state Zonisamide concentrations.

Clinical Utility

Zonisamide is approved as adjunct therapy in the treatment of partial seizures in adults with epilepsy.

CPT Code


Test Codes

Antrim #19574, EPIC: LAB5433, SOFT: ZONIS

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This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.