Lamotrigine, Serum or Plasma

Casandra

Casandra Test Code LC31894Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 716944CPT Code 80175

Lamotrigine, Serum or Plasma

Also known as: Lamictal®

Clinical Use

Order Test

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.

Test Details