Topiramate, Serum
Use
Topiramate is a broad spectrum, antiepileptic drug employed for managing various types of seizures, Lennox-Gastaut syndrome, and migraine prophylaxis. This test is crucial for monitoring serum concentrations of topiramate to ensure therapeutic levels, assess patient compliance, and evaluate potential toxicity. The drug blocks voltage-dependent sodium channels, potentiates gamma-aminobutyric acid (GABA) activity, and inhibits glutamate receptors, contributing to its efficacy. Given its renal elimination, monitoring is particularly important in patients with impaired kidney function. The test assists in therapeutic drug monitoring, especially when co-administering with other medications that can affect topiramate levels, such as phenytoin and carbamazepine.
Special Instructions
When ordering non-electronically, please complete the relevant forms provided on the website for Neurology Specialty Testing or Therapeutics Test requests. For accurate results, specimen collection should occur immediately before the next topiramate dose. Additional considerations include potential interactions with drugs like phenytoin and posaconazole, which may alter topiramate concentration.
Limitations
This test cannot be performed on whole blood samples; only serum is accepted. Furthermore, while therapeutic ranges are provided, individual patient response may vary, and clinical evaluation is necessary as levels outside the typical range may still reflect effective or toxic conditions. Note that other anticonvulsant drug levels are generally not affected by topiramate, though phenytoin levels may increase. Proper specimen handling and processing are crucial as serum gel tubes are not acceptable, and any deviation might lead to rejection.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 17713-9
- 17713-9
Result Turnaround Time
1-4 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Plastic vial
Collection Instructions
Draw blood immediately before next scheduled dose. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial. Use a red top collection container; serum gel/SST are not acceptable.
Causes for Rejection
Serum gel tubes are not acceptable.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 28 days |
| Refrigerated | 28 days |
| Frozen | 28 days |