Lamotrigine, Serum or Plasma

CPT: 80175
Print Share

Synonyms

  • Lamictal®

Expected Turnaround Time

2 - 5 days


Related Documents


Specimen Requirements


Specimen

Serum or plasma


Volume

1 mL


Minimum Volume

0.3 mL (Note: This volume does not allow for repeat testing.)


Container

Red-top tube, lavender-top (EDTA) tube, or green-top (heparin) 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.


Collection

Transfer separated serum or plasma to a plastic transport tube.


Storage Instructions

Maintain specimen at room temperature.


Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

7 days

Frozen

28 days

Freeze/thaw cycles

Stable x3


Causes for Rejection

Gel-barrier tube; whole blood samples; unspun samples that are not separated from cells


Test Details


Methodology

Homogeneous Immunoassay


Reference Interval

Therapeutic: trough: 2.0−20.0 μg/mL


Additional Information

Lamotrigine is an antiepileptic drug (AED) of the phenyltriazine class that is chemically unrelated to existing AEDs. The precise mechanism of action is unknown although it has been postulated that lamotrigine inhibits voltage-sensitive sodium channels thereby stabilizing neuronal membranes and consequently modulating presynaptic transmitter release of excitatory amino acids (eg, glutamate, aspartate). Lamotrigine is 55% bound to plasma proteins and is metabolized predominantly to an inactive 2-N-glucuronide conjugate. Peak plasma concentration occurs at 1.4 to 4.8 hours following oral administration.1 The elimination half-life varies from 12 to 70 hours. The longer half-lives are observed in patients on concomitant valproic acid therapy. Accordingly, if lamotrigine is coadministered with valproic acid, the dose of lamotrigine must be reduced to less than half the normal dosage. The most common adverse reactions are associated with the use of lamotrigine in combination with other anticonvulsants, and include dizziness, diplopia, ataxia, blurred vision, nausea and vomiting, somnolence, headache, and rash. The anticonvulsants phenytoin, phenobarbital, primidone, and carbamazepine can reduce lamotrigine levels when coadministered.2 Conversely, lamotrigine can reduce levels of levetiracetam when coadministered.3 In children, investigators4 have found large differences in lamotrigine plasma levels in patients with improvement in seizure frequency, but patients who were seizure-free had higher lamotrigine levels than other patients in the study.


Footnotes

1. ARK Lamotrigine Assay [package insert]. Fremont, CA: ARK Diagnostic Inc;1600-0179-00 Rev 04, Feb 2017.
2. Patsalos PN, Berry DJ, Bourgeois BDF, et al. Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: A position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies. Epilepsia. 2008 Jul;49(7):1239-1276.18397299
3. Morris RG, Black AB, Harris AL, Batty, AB, Sallustio BC. Lamotrigine and therapeutic drug monitoring: Retrospective survey following the introduction of a routine service. Br J Clin Pharmacol. 1998 Dec;46(6):547-551.9862243
4. Johannessen SI, Battino D, Berry DJ, et al. Therapeutic drug monitoring of the newer antiepileptic drugs. Ther Drug Monit. 2003 Jun;25(3):347-363.12766564

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
716944 Lamotrigine (Lamictal), Serum 6948-4 716945 Lamotrigine, Serum ug/mL 6948-4

For Providers

Please login to order a test

Order a Test

© 2021 Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.

CPT Statement/Profile Statement

The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf