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Test Code OMHC Oxcarbazepine Metabolite (MHC), Serum

Reporting Name

Oxcarbazepine Metabolite (MHC), S

Useful For

Monitoring serum concentration during oxcarbazepine therapy

 

Assessing compliance

 

Assessing potential toxicity

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Serum Red


Specimen Required


Container/Tube:

Preferred: Red top

Specimen Volume: 1 mL

Collection Instructions:

1. Draw specimen immediately before next scheduled dose.

2. Spin down within 2 hours of draw.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

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

Reference Values

Oxcarbazepine metabolite: 3-35 mcg/mL

Day(s) and Time(s) Performed

Tuesday through Saturday; 12 a.m., Saturday; 1 p.m.

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

80183

LOINC Code Information

Test ID Test Order Name Order LOINC Value
OMHC Oxcarbazepine Metabolite (MHC), S In Process

 

Result ID Test Result Name Result LOINC Value
81030 Oxcarbazepine Metabolite (MHC), S 31019-3

Clinical Information

Oxcarbazepine (OCBZ) is approved as monotherapy and adjunctive therapy for partial seizures with and without secondary generalized seizures in adults and as adjunctive therapy for partial seizures in children. In humans, OCBZ is a prodrug that is almost immediately and completely metabolized to 10-hydroxy-10,11-dihydrocarbamazepine, known as monohydroxycarbamazepine (MHC), an active metabolite that is responsible for OCBZ's therapeutic effect. The elimination half-life is 1 to 2.5 hours for OCBZ and 8 to 10 hours for MHC. The therapeutic range (3–35 mcg/mL) is based on concentrations of the metabolite, not the parent drug; this assay measures the metabolite only.

 

In clinical practice, the OCBZ dosage should be individually adjusted for each patient to achieve the desired therapeutic response. Toxicity associated with OCBZ includes hyponatremia, dizziness, somnolence, diplopia, fatigue, nausea, vomiting, ataxia, abnormal vision, abdominal pain, tremor, dyspepsia, and abnormal gait. These toxicities may be observed when blood concentrations are in the therapeutic range.

Interpretation

Therapeutic ranges are based on specimens drawn at trough (ie, immediately before the next dose). Most individuals display optimal response to oxcarbazepine therapy when serum levels of the metabolite (measured in this assay) are between 3 and 35 mcg/mL. Some individuals may respond well outside of this range, or may display toxicity within the therapeutic range. Thus, interpretation should include clinical evaluation.

Clinical Reference

1. Patsalos P, Berry D, Bourgeois B, 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;49(7):1239–1276

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

Analytic Time

Same day/1 day

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

Method Name

High-Turbulence Liquid Chromatography Mass Spectrometry (HTLC-MS/MS)

Forms

If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)

Secondary ID

81030