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HelpTest Code OMHC Oxcarbazepine Metabolite, Serum
Reporting Name
Oxcarbazepine Metabolite (MHC), SUseful For
Monitoring serum concentration during oxcarbazepine therapy
Assessing compliance
Assessing potential toxicity
Method Name
High-Turbulence Liquid Chromatography Mass Spectrometry (HTLC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST is not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Collect specimen immediately before next scheduled dose.
2. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
Oxcarbazepine metabolite: 10-35 mcg/mL
Day(s) Performed
Monday through Saturday
CPT Code Information
80183
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| OMHC | Oxcarbazepine Metabolite (MHC), S | 31019-3 |
| 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 monohydroxy carbamazepine (MHC), an active metabolite that is responsible for OCBZ's therapeutic effect. The elimination half-life is approximately 2 hours for OCBZ and 7 to 11 hours for MHC. The therapeutic range (10-35 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 collected 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 10 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.
Cautions
Toxic levels have not been well established.
This test cannot be performed on whole blood. Serum must be separated from cells within 2 hours of collection.
Method Description
The serum sample is diluted in acetonitrile containing internal standard. The protein precipitate is centrifuged, and a portion of the supernatant is diluted with mobile phase for detection by a tandem mass spectrophotometer.(Unpublished Mayo method)