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Test Code LAMO Lamotrigine, Serum

Important Note

ASANTE order code: LAMOB

Epic/Beaker order is LAB475

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

Lamotrigine, S

Specimen Type

Serum


Specimen Required


Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Collection Instructions: Draw specimen immediately before next scheduled dose or at least 12 hours after last dose.


Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

 

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Specimen Minimum Volume

0.5 mL

Day(s) and Time(s) Performed

Monday through Friday; 2 p.m.,

Saturday; 1 p.m.,

Sunday; 11 a.m.

Specimen Retention Time

14 days

Analytic Time

Same day/1 day

Reference Values

Patients receiving therapeutic doses usually have lamotrigine concentrations of 2.5-15.0 mcg/mL.

Useful For

Monitoring serum concentration of lamotrigine

 

Assessing compliance

 

Adjusting lamotrigine dose in patients receiving other anticonvulsant drugs which interact pharmacokinetically with lamotrigine

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

80175

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LAMO Lamotrigine, S 6948-4

 

Result ID Test Result Name Result LOINC Value
80999 Lamotrigine, S 6948-4

Clinical Information

Lamotrigine (Lamictal) is approved for therapy of bipolar I disorder and a wide variety of seizure disorders including Lennox-Gastaut syndrome, primary generalized tonic-clonic seizures, and partial seizures. Its many off-label uses include treatment of migraine, trigeminal neuralgia, and treatment-refractory depression. Lamotrigine inhibits glutamate release (an excitatory amino acid) and voltage-sensitive sodium channels to stabilize neuronal membranes; it also weakly inhibits the 5-HT3 (serotonin) receptor.

 

Lamotrigine oral bioavailability is very high (approximately 98%).The drug is metabolized by glucuronic acid conjugation to inactive metabolites. The half-life is 25 to 33 hours in adults, but decreases with concurrent use of phenytoin or carbamazepine (13-14 hours), and increases with concomitant valproic acid therapy (59-70 hours), renal dysfunction, or hepatic impairment. The therapeutic range is relatively wide, 2.5 to 15 mcg/mL for most individuals. Common adverse effects are dizziness, ataxia, blurred or double vision, nausea, or vomiting.

Interpretation

The serum concentration should be interpreted in the context of the patient's clinical response and may provide useful information in patients showing poor response (noncompliance?) or adverse effects, particularly when lamotrigine is co-administered with other anticonvulsant drugs.

 

While most patients show response to the drug when the trough concentration is in the range of 2.5 to 15.0 mcg/mL, and show signs of toxicity when the peak serum concentration is >20 mcg/mL, some patients can tolerate peak concentrations as high as 70 mcg/mL.

Cautions

Serum separator tube acceptable but serum should be removed from gel within 24 hours.

Clinical Reference

1. Johannessen SI, Battino D, Berry DJ, et al: Therapeutic drug monitoring of the newer antiepileptic drugs. Ther Drug Monit 2003;25(3):347-363

2. Johannessen SI, Landmark CJ: Value of therapeutic drug monitoring in epilepsy. Expert Rev Neurother 2008;8(6):929-939

3. Johannessen SI, Tomson T: Pharmacokinetic variability of newer antiepileptic drugs: when is monitoring needed? Clin Pharmacokinet 2006;45(11):1061-1075

4. Physician's Desk Reference. 61st Edition. Montvale, NJ: Thomson PDR, 2007

5. Goodman and Gilman's: The Pharmacological Basis of Therapeutics. 10th Edition. New York. McGraw-Hill Book Company 2001

Method Description

Samples are diluted and extracted online extraction by high turbulence liquid chromatography, with detection by tandem mass spectrometry.(Unpublished Mayo method)

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

Neurology Specialty Testing Client Test Request (T732) (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)

General Request Form (T239) (http://www.mayomedicallaboratories.com/it-mmfiles/general-request-form.pdf)