Lab Test

Topiramate Level


Test Codes

Antrim #31435, EPIC: LAB5426, SOFT: TOPIR



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/Draw Specimen Preparation

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

Preparation for Courier Transport

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

Rejection Criteria

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

In-Lab Processing

Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Deliver an aliquot of serum or the collection tube immediately to the appropriate testing station.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 1 months


Royal Oak Toxicology Laboratory


Sunday – Saturday.
Results available the same day as testing performed.

Reference Range

Therapeutic Range: 5-25 mcg/mL.
Critical Value: 40 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.


Topiramate is distributed extensively to red blood cells. Hemolysis will falsely elevate serum measurements. The Topiramate elimination half-life is about 24 hours with a time to steady-state of 4 days for the average patient. Topiramate is eliminated by renal and metabolic means. A decline in renal function will increase Topiramate steady-state concentrations and hemodialysis will decrease concentrations requiring supplemental dosing. Concurrent drugs that induce hepatic metabolism [Phenytoin, Carbamazepine] may decrease steady-state Topiramate concentrations. Co-administration with Lamotrigine may increase Topiramate concentrations by 15%.

Clinical Utility

Topiramate is approved as monotherapy in patients 10 years of age or older with partial onset or primary generalized tonic-clonic seizures. It is also approved as adjunct therapy in the treatment of partial onset seizures or primary generalized tonic-clonic seizures in adults and children between the ages of 2 to 16 years. It is approved for treatment of patients 2 years of age or older for Lennox-Gastaut syndrome. It is approved for the prophylactic management of migraine in adults.

CPT Codes

LOINC: 17713-9


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