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Lamotrigine (LAM)

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EPIC Test Name

LAMOTRIGINE

EPIC Code

LAB2475

Specimen Requirements

serum
Minimum Volume:0.5 mL
Collection:Collect specimens using standard laboratory procedures.
Transport:Room Temperature ASAP
Stability:Room Temperature: 7 days capped at 20-25 degrees C
Refrigerated: 7 days capped at 2-8 degrees C
Frozen: 4 weeks capped at -20 degrees C
Container:Red
Rejection Causes:Hemolysis, lipemic,
Insufficient Sample Volume
Notes:Do not use gel separator tube.

Methods

Homogeneous particle-enhanced turbidimetric immunoassay

Turnaround Time

SpecimenTurnaround TimeFrequency
serumRoutine: 4 hours24/7

Reference Ranges

Homogeneous particle-enhanced turbidimetric immunoassay
UnitTherapeutic Levels
µg/mL3.0-14 µg/mL

Clinical Indications

Lamotrigine (Lamictal®) is an anticonvulsant agent, and particular effective as an adjunctive therapy on several seizure types, e.g., partial, generalized tonic-clonic, typical and atypical absence seizures and Lennox-Gastaut syndrome (LGS). Lamotrigine is considered a broad-spectrum antiepileptic drug, and it is like carbamazepine, uses as a monotherapy in treatment of bipolar disorder and as a mood stabilizer. The mechanism of action of the drug may be its inhibition of glutamate release (an excitatory amino acid), voltage-sensitive sodium and calcium channels to stabilize neuronal membranes, and the 5-HT3 (serotonin) receptor.
Lamotrigine oral bioavailability is nearly 100%. About 50% of the drug are protein bound and reaches peak plasma concentrations 1-3 hours after administration. The drug is metabolized by glucuronic acid conjugation to inactive metabolites and cleared via kidneys. The half-life is 15-30 hours in adults but slightly longer in children. The drug metabolizing/elimination rate can be affected by many factors, e.g., a concurrent use of phenytoin or carbamazepine (T1/2 decrease to 13-14 hours) and valproic acid (increases to about 59-70 hours), renal dysfunction, and hepatic impairment. The therapeutic range is relatively wide, 2.5 to 15 mcg/mL for most individuals. Lamotrigine’s most common side effects include headache, nausea, infection and insomnia. The other side effects also include but not limited to incidence of diarrhea, tremor and rash. Lamotrigine is measured for therapeutic drug monitoring. Trough concentrations are typically 1-2 µg/mL, and toxic effects can be seen at > 20 µg /mL.

Additional Information

If using serum separator tube for sample collection, serum portion should be removed from gel within 24 hours of collection.

Performed

Lab
Chemistry - Downtown

Interpretative Information

Measured drug concentration should be interpreted with consideration of patient's clinical response and presence/absence of adverse effects, and especially when co-administered with other antiepileptic drugs.

CPT

80175

LOINC

6948-4

References

1. Marzinke A and Clarke W. Antiepileptic drugs. In The Clinical Toxicology Laboratory – contemporary practice of poisoning evaluation. ed. by Tai Kwong, etc., 2nd ed. Page 235-60.
2. 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.
3. Johannessen SI, Landmark CJ: Value of therapeutic drug monitoring in epilepsy. Expert Rev Neurother. 2008 Jun;8(6):929-939
4. Hiemke C, Bergemann N, Clement HW, et al: Consensus guidelines for therapeutic drug monitoring in neuropsychopharmacology: Update 2017. Pharmacopsychiatry. 2018;51(1-02):9-62

Contact Information

Chemistry - Downtown: (315)464-4460
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