Test ID CARF Carbamazepine, Free, Serum
Useful For
Monitoring carbamazepine (free) therapy in uremic patients
Method Name
Ultrafiltration Followed by Immunoassay
Reporting Name
Carbamazepine, Free, SSpecimen Type
Serum RedContainer/Tube: Red top
Specimen Volume: 2 mL
Collection Instructions: Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.
Specimen Minimum Volume
1 mL
Specimen Stability Information
Specimen Type | Temperature | Time |
---|---|---|
Serum Red | Refrigerated (preferred) | 14 days |
Frozen | 28 days | |
Ambient | 14 days |
Clinical Information
Carbamazepine (Tegretol) is an effective treatment for complex partial seizures, with or without generalization to tonic-clonic seizures. It is frequently administered in conjunction with other antiepileptic agents, such as phenytoin and valproic acid. Under normal circumstances, the carbamazepine that circulates in blood is 75% protein-bound. In severe uremia, carbamazepine may be displaced from protein resulting in a higher free (unbound) fraction of the drug circulating in blood. Since neurologic activity and toxicity of carbamazepine are directly related to the circulating free fraction of drug, adjustment of dosage based on knowledge of the free carbamazepine level may be useful in patients with severe uremia.
Reference Values
Therapeutic concentration: 1.0-3.0 mcg/mL
Critical value: ≥4.0 mcg/mL
Cautions
Fresh serum with normal protein content is required for optimal analysis.
Specimens subjected to significant heat or other factors that cause protein denaturation may demonstrate an artifactually increased free carbamazepine level.
Day(s) Performed
Monday through Sunday; ContinuouslyReport Available
Same day/1dayPerforming Laboratory

Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
80157