Lamotrigine, Serum or Plasma
Also known as: Lamictal®
Use
Lamotrigine is an antiepileptic drug (AED) used to treat epilepsy by inhibiting voltage-sensitive sodium channels. This action stabilizes neuronal membranes and modulates presynaptic transmitter release of excitatory amino acids. The drug is 55% bound to plasma proteins and is metabolized predominantly to an inactive 2-N-glucuronide conjugate. Peak plasma concentration occurs 1.4 to 4.8 hours following oral administration, and the elimination half-life varies from 12 to 70 hours, being longer in patients on concomitant valproic acid therapy.
Special Instructions
The most common adverse reactions occur when lamotrigine is combined with other anticonvulsants, causing dizziness, diplopia, ataxia, blurred vision, nausea, vomiting, somnolence, headache, and rash. Phenytoin, phenobarbital, primidone, and carbamazepine can reduce lamotrigine levels, whereas lamotrigine can decrease levetiracetam levels. Children with improved seizure frequency had varying plasma levels of lamotrigine, but seizure-free patients showed higher levels.
Limitations
Lamotrigine levels can be influenced by other anticonvulsants. Gel-barrier tubes should not be used due to drug absorption issues, potentially causing clinically significant decreases in drug levels. Specimens must be stored properly to maintain accuracy, as incorrect handling may affect the results. Freeze/thaw cycles should be limited to three to prevent degradation of the sample.
Methodology
Immunoassay (Homogeneous Immunoassay)
Biomarkers
LOINC Codes
- 6948-4
- 6948-4
Result Turnaround Time
2-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.3 mL
Container
Red-top tube
Collection Instructions
Transfer separated serum or plasma to a plastic transport tube.
Storage Instructions
Maintain specimen at room temperature.
Causes for Rejection
Gel-barrier tube; whole blood samples; unspun samples that are not separated from cells
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 7 days |
| Frozen | 28 days |
Other tests from different labs that may be relevant