Fluoxetine, Serum
Use
This test is useful for monitoring serum concentration of fluoxetine during therapy to evaluate potential toxicity and patient compliance. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI), commonly used for the treatment of bulimia, obsessive-compulsive behavior, panic disorders, premenstrual dysphoria, and major depressive disorder. The test measures both fluoxetine and its major metabolite, norfluoxetine, which are pharmacologically active. Optimal response is expected when the combined serum concentrations are within the therapeutic range of 120-500 ng/mL at steady state.
Special Instructions
Draw blood immediately before the next scheduled dose (trough). Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial. If not ordering electronically, complete and send the Therapeutics Test Request form with the specimen.
Limitations
Specimens obtained using gel tubes or anticoagulant collections can cause falsely decreased results or assay interference. There is wide interindividual variability in fluoxetine pharmacokinetics due to its long half-life and interactions with the cytochrome P450 system, particularly CYP2D6, CYP2C19, and CYP3A. These interactions, along with the slow steady-state achievement, can affect the accuracy of serum level interpretations. Toxicity levels are not well established and may occur even within the therapeutic range.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 78437-1
- 74982-0
- 3868-7
- 74948-1
Result Turnaround Time
1-8 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Red top (serum gel/SST are not acceptable); plastic vial for submission.
Collection Instructions
Draw blood immediately before the next scheduled dose (trough). Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Causes for Rejection
Specimens collected in gel tubes or using anticoagulants.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 72 hours |
| Refrigerated | 28 days |
| Frozen | 28 days |