Leflunomide Metabolite (Teriflunomide), Serum
Use
Leflunomide is a disease-modifying antirheumatic drug approved for therapy of rheumatoid arthritis and is used off-label to reduce viral nephritis in kidney transplant. It is a prodrug that converts to its active metabolite, teriflunomide, which inhibits pyrimidine synthesis. Due to variability in leflunomide pharmacokinetics, therapeutic monitoring of serum teriflunomide concentrations can aid in optimizing therapy. Serum concentrations greater than 40 mcg/mL have been correlated with better outcomes, especially in managing adverse reactions like diarrhea, hypertension, and liver toxicity. Assessment may be necessary for patients planning pregnancy due to potential teratogenic risks associated with the drug.
Special Instructions
Trough sampling for serum is recommended for consistency due to the long half-life of teriflunomide, though samples may be collected at any point in the dosing cycle. It's important to ensure the sample is drawn no sooner than 12 hours after the last dose for accurate therapeutic monitoring.
Limitations
Leflunomide toxicity might not correlate with Teriflunomide concentrations, limiting this assay's usefulness for evaluating potential adverse drug reactions. Serum concentrations must be assessed over two independent tests, at least two weeks apart, to guide therapeutic adjustments accurately, especially for patients considering pregnancy.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 44828-2
- 44828-2
Result Turnaround Time
3-5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.3 mL
Container
Plastic vial
Collection Instructions
Draw blood no sooner than 12 hours after last dose. Centrifuge and aliquot into a plastic vial within 2 hours of collection.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 28 days |
| Refrigerated | 28 days |
| Frozen | 28 days |