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Test Name:
Topiramate, Serum or Plasma
- SBMF No:
23125 - Performance Lab Name:
Automated Lab - Test Mnemonic:
TOPIR - ABN:
Not required - CPT Code:
80201 - LOINC Code:
17713-9 - Also Known As:
Topamax - Spec Type:
Serum - Spec Container:
Red top (serum) tube - Alt Spec Type:
Plasma - Alt Spec Container:
Green top (lithium heparin) tube - Pref Vol:
0.5 mL - Min Vol:
0.2 mL - Fasting:
No - Spec Collect:
Do not use gel-barrier tubes for specimen collection
Routine venipuncture - Spec Process:
Serum sample tubes, clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum or plasma to separate plastic tube - Spec Store Transport:
Refrigerated (24 hours) or frozen - Spec Stability:
24 hours refrigerated (2-8°C)
3 months frozen (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles - Spec Reject:
Sample collected in EDTA tube - Methodology:
Fluorescence Polarization - Use:
Monitor Topiramate therapy to ensure the patient is receiving a dose adequate to achieve anti-epileptic activity while avoiding side effects associated with high blood levels - Clinical Significance:
Topiramate, an anticonvulsant drug used in the treatment of epilepsy, is a sulfamate-substituted monosaccharide, structurally dissimilar to other standard anticonvulsant drugs. Topiramate is routinely administered orally, absorbed rapidly and metabolized minimally. Peak plasma concentrations are reached 2-3 hours after dosing. Binding to plasma proteins is low, normally less than 15%. Elimination is predominantly renal as analtered Topiramete, with an elimination half-life of 20-30 hours. - Reference Range:
Peak: 9-12 mg/mL
Trough: 2-4 mg/mL - Additional Test Info:
Interpretation: Plasma concentrations of other anticonvulsant drugs are not significantly affected by the concurrent administration of Topiramate, with exception in individual patients on phenytoin exhibiting increased phenytoin plasma concentrations after addition of Topiramate. Coadministration of phenytoin or carbamazepine decreases Topiramate plasma concentrations. Changes in co-therapy with phenytoin or carbamazepine (e.g. addition or withdrawal) for patients stabilized on Topiramate therapy may require Topiramate dose adjustment. As with other renally eliminated anticonvulsant drugs, patients with impaired renal function exhibit decreased renal clearance. In clinical trials, Topiramate concentrations have generally ranged from 2 25 mg/mL. Dose adjustment should be guided by clinical outcome. Circulating Topiramate levels have not been correlated to toxicity, adverse affects, or clinical efficacy. Results must be interpreted by the clinician by consideration of co-administered drugs and all other confounding factors. - Day Run:
Sun-Sat (daily) - Time Run:
As received - Time Reported:
8 hours - Test Type:
TOX-TDM
