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HelpEPIC ORDER CODE LAB475 Lamotrigine, Serum
Additional Codes
SQ: LAMOTM
Reporting Name
Lamotrigine, SUseful For
Monitoring serum concentration of lamotrigine
Assessing compliance
Adjusting lamotrigine dose in patients receiving other anticonvulsant drugs that interact pharmacokinetically with lamotrigine
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Collect blood immediately before next scheduled dose.
2. For sustained-release formulations only, collect blood a minimum of 12 hours after last dose.
3. Centrifuge within 2 hours of collection
4. For red-top tubes, immediately aliquot serum into a plastic vial.
5. For serum gel tubes, aliquot serum into a plastic vial within 24 hours of collection.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reference Values
Patients receiving therapeutic doses usually have lamotrigine concentrations of 3.0-15.0 mcg/mL.
Day(s) Performed
Monday through Sunday
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US 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), kidney dysfunction, or hepatic impairment. The therapeutic range is relatively wide, 3 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 coadministered with other anticonvulsant drugs.
While most patients show response to the drug when the trough concentration is in the range of 3.0 to 15.0 mcg/mL and show signs of toxicity when the peak serum concentration is greater than 20 mcg/mL, some patients can tolerate peak concentrations as high as 70 mcg/mL.
Clinical Reference
1. Milone MC, Shaw LM: Therapeutic drugs and their management. In: Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:420-453
2. Johannessen SI, Battino D, Berry DJ, et al. Therapeutic drug monitoring of the newer antiepileptic drugs. Ther Drug Monit. 2003;25(3):347-363. doi:10.1097/00007691-200306000-00016
3. Johannessen SI, Landmark CJ. Value of therapeutic drug monitoring in epilepsy. Expert Rev Neurother. 2008;8(6):929-939. doi:10.1586/14737175.8.6.929
4. Johannessen SI, Tomson T. Pharmacokinetic variability of newer antiepileptic drugs: When is monitoring needed? Clin Pharmacokinet. 2006;45(11):1061-1075. doi:10.2165/00003088-200645110-00002
5. Physician's Desk Reference. 71st ed. Thomson PDR; 2017
6. Hardman JG, Limbird LE, Gilman AG, eds. Goodman and Gilman's The Pharmacological Basis of Therapeutics. 10th ed. McGraw-Hill Book Company; 2001
7. 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. doi:10.1055/s-0043-116492
Method Description
Samples are diluted and extracted online by high turbulence liquid chromatography with detection by tandem mass spectrometry.(Unpublished Mayo method)
Report Available
Same day/1 to 2 daysSpecimen Retention Time
14 daysReject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Forms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-Neurology Specialty Testing Client Test Request (T732)
-General Request (T239)
-Therapeutics Test Request (T831)