Levetiracetam (Keppra®), Serum
| Levetiracetam (Keppra®), Serum | | | |
| Number | | 716936 |
| CPT | | 82491 |
| Synonyms | | Keppra® |
| Specimen | | Serum or plasma |
| Volume | | 1 mL |
| Minimum Volume | | 0.2 mL |
| Container | | Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) tube |
Collection | | Transfer separated serum or plasma to a plastic transport
tube. Do not use a gel-barrier tube; the use of
gel-barrier tubes is not recommended due to slow absorption
of the drug by the gel. Depending on the specimen volume
and storage time, the decrease in drug level due to
absorption may be clinically significant. |
| Storage Instructions | | Maintain specimen at room temperature. |
| Causes for Rejection | | Gel-barrier tube |
| Reference Interval | | 5-63 μg/mL |
| Methodology | | High-pressure liquid chromatography (HPLC) and/or liquid chromatography mass spectrometry (LC/MS) |
| Additional Information | | Levetiracetam (LTA), a piracetam analogue, is an antiepileptic drug (AED) structurally unrelated to other AEDs. The exact mechanism by which LTA acts has not been determined at this time; however, binding sites for the drug have been identified in synaptic plasma membranes of CNS neurons. Secondary alteration in GABA-related enzymes may result from binding to neurons in specific regions of the CNS.1 While approximately one-fourth of LTA is converted by enzymatic hydrolysis to a carboxylic acid metabolite, the drug has no effect on UDP glucuronyltransferase, epoxide hydrolase, or enzymes in the CYP system,1,2 resulting in minimal interactions with other AEDs in a polypharmacy regimen. LTA has minimal protein binding (<10%), an elimination half-life of 6-8 hours in healthy adults, 6 hours in children, and 10-11 hours in the elderly. In healthy adults, approximately 95% of LTA and metabolites are excreted in the urine. Renal impairment can, therefore, decrease clearance from 35% to 60%.3,4 A single 1000 mg dose or 1000 mg twice daily doses produced peak levels of 31 μg/mL and 43 μg/mL, respectively.3 Neuropsychiatric adverse events of aggression, anger, and irritability, as well as adverse reactions of leukopenia, neutropenia, pancytopenia, and thrombocytopenia have been reported.5 |
| Footnotes | |
1. Willmore LJ. Clinical pharmacology of new
antiepileptic drugs. Neurol. 2000; 55(Suppl
3):S17-24.
2. Wheless JW. Using the new antiepilepsy drugs in
children. J Child Neurol. 2002; 17(Suppl
1):S58-64.
3. Patsalos PN. Pharmacokinetic profile of
levetiracetam: Toward ideal characteristics. Pharm
Ther. 2000; 85:77-85.
4. Radtke RA. Pharmacokinetics of levetiracetam.
Epilepsia. 2001; 42(Suppl 4):24-7.
5. FDA Center for Drug Evaluation and Research (CDER),
MedWatch Report, May 22, 2002 |
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