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General
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Clinical Use:
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Topiramate is sulfamate-substituted monosaccharide, anti-convulsant used for partial onset, tonic-clonic seizures, Lennox-Gastaut syndrome and migraine prophylaxis in adults. Topiramate blocks sodium channels, potentiates gamma-aminobutyric acid (GABA) activity, and inhibits potentiation of the glutamate receptor, allowing the drug to block seizure spread.
Topiramate may decrease serum bicarbonate concentrations because of inhibition of carbonic anhydrase and increased renal bicarbonate loss, leading to metabolic acidosis. Other adverse effects may include: CNS disturbance; incl drowsiness, dizziness, paraesthesia, ataxia, depression, personality & speech disorder, fatigue, weight loss, GI upset, oligohidrosis, and hyperthermia. |
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Availability:
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Aliases/Synonyms:
| Topamax, |
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Code:
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TOP |
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Handling Instructions (to laboratory):
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Send sample chilled. |
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Hyperlink:
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Reference Interval:
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The relationship between plasma levels of topiramate and clinical outcome has not yet been established. Peak plasma concentrations are reached 2 to 4 hours after dosing. The half life of topiramate is 20-30 hours.
P
eak plasma concentration increases proportionally with dosage - see below:
Topiramate oral dose 100 mg - peak plasma level (mean) 5 umol/L - peak time 1.8 hrs.
Topiramate oral dose 200 mg - peak plasma level(mean) 10.9 umol/L - peak time 1.4 hrs.
Topiramate oral dose 400 mg - peak plasma level (mean) 22.7 umol/L - peak time 3.5 hrs.
Topiramate oral dose 800 mg - peak plasma level (mean) 54.2 umol/L - peak time 4.3 hrs.
Topiramate oral dose 1600 mg - peak plasma level (mean) 84.6 umol/L - peak time 3.8 hrs.
Conversion: umol/L x 0.3394 = ug/L
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Collection Requirements
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Container:
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Serum, no gel (RED), |
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Sample Type:
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See container |
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Minimum Collection Volume:
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Collection Instructions:
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Sample should be collected 2-4 hours post dose.
Record date, time and dosage of last dose on request form. |
Processing Requirements
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Alternate Containers:
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Lithium Heparin, No Gel (DKGNLITH) |
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Processing Instructions:
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Centrifuge, separate and freeze sample. |
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Minimum Assay Volume:
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1mL |
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Stability:
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Transport Instructions (to testing laboratory):
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Send separated sample frozen on dry ice. |
Testing Locations
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Performed at:
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Section
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Department
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Site
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Contact Phone
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Laboratory |
SSWPS-Royal Prince Alfred Hospital |
(02) 9515 8279 |
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Last Updated : 19-12-2025 11:45 |