81992:CARBAMAZEPINE, FREE and TOTAL

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81992:CARBAMAZEPINE, FREE and TOTAL
Alias Names: Tegretol
Methodology: Immunoassay
Edit Date: 11/16/2010
Components: Carbamazepine, Total / Carbamazepine, Free (Carbamazepine Free is not available without a Carbamazepine Total.)
Performed: Monday-Friday
Released: 1-4 days after setup at PeaceHealth Laboratories’ reference lab.
CPT Code: 80156-90 / 80157-90
Specimen Collection Details
Collection: One 5 mL red top tube. Do not use serum separator tube (SST).
Handling: Allow to clot, centrifuge and immediately separate serum from cells into a plastic vial. Refrigerate.
Stability: 5 days ambient, 5 days refrigerated, or 4 months frozen.
Standard Volume: 2 mL serum
Minimum Volume: 1 mL serum
Transport: Refrigerated.
Comments: Free carbamazepine may be important to monitor in patients with altered or unpredictable protein binding capacity. Carbamazepine is also subject to drug-drug interactions due to displacement of protein binding and extensive metabolism. Cross-reactivity with metabolites may account for differences in carbamazepine among analytical methods. Calculating percent free attempts to minimize differences in assay cross-reactivity and may be useful in dose optimization.
Rejection Criteria: Use of SST or PST; EDTA or heparin plasma.

Reference Range:
Carbamazepine, Total Therapeutic Range: 4.0-12.0 µg/mL
Toxic Range: > 20 µg/mL
Carbamazepine, Free Therapeutic Range: 1.0-3.0 µg/mL
Toxic Range: > 3.8 µg/mL
Percent Free Carbamazepine 8.0-35.0%

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