Skip Ribbon Commands
Skip to main content
Sign In

22635 Fluoxetine, Serum (FLUOX)

Fluoxetine, Serum (FLUOX)
Test Code: FLUOX
Synonyms/Keywords
Fluoxetine (Prozac), Norfluoxetine, Prozac (Fluoxetine Hydrochloride)
Useful For
​Monitoring serum concentration of fluoxetine during therapy
 
Evaluating potential toxicity
 
Evaluating patient compliance
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Serum Red Top Tube (RTT)​ 1 mL​ 0.5 mL​
Collection Processing Instructions
​Spin down and separate serum from cells within 2 hours of draw.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​ ​ Refrigerated (preferred)​ 28 days​
Frozen ​ 28 days​
Ambient 72 hours​
Rejection Criteria
​Serum gel tube
Interference

​Specimens that are obtained from gel tubes or anticoagulate collections can cause assay interference.

Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories
Wednesday
1-8 days
Liquid Chromatography- Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
Test Information

​Fluoxetine is a selective serotonin reuptake inhibitor approved for treatment of bulimia, obsessive-compulsive behavior, panic disorders, premenstrual dysphoria, and major depressive disorder, with a variety of off-label uses. Both fluoxetine and its major metabolite, norfluoxetine, are pharmacologically active and are reported together in this assay. Most individuals respond optimally when combined serum concentrations for both parent and metabolite are in the therapeutic range (120-500 ng/mL) at steady state. Due to the long half-lives of parent and metabolite (1-6 days), it may take several weeks for patients to reach steady-state concentrations. Fluoxetine is a potent inhibitor of the metabolic enzyme cytochrome P450 (CYP) 2D6, with lesser inhibitory effects on CYP2C19 and CYP3A. Therapy with fluoxetine is, therefore, subject to numerous drug interactions, which is compounded by wide interindividual variability in fluoxetine pharmacokinetics. Measurement of the drug is useful for managing comedications, dose or formulation changes, and in assessing compliance. Side effects are milder for fluoxetine than for older antidepressants such as the tricyclics. The most common side effects of fluoxetine therapy include nausea, nervousness, anxiety, insomnia, and drowsiness. Anticholinergic and cardiovascular side effects are markedly reduced compared to tricyclic antidepressants. Fatalities from fluoxetine overdose are extremely rare.

Reference Range Information
Fluoxetine + Norfluoxetine: 120-500 ng/mL
Interpretation
​Most individuals display optimal response to fluoxetine when combined serum levels of fluoxetine and norfluoxetine are between 120 and 300 ng/mL. Some individuals may respond well outside of this range or may display toxicity within the therapeutic range, thus interpretation should include clinical evaluation. A toxic range has not been well established.
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80299
Synonyms/Keywords
Fluoxetine (Prozac), Norfluoxetine, Prozac (Fluoxetine Hydrochloride)
Ordering Applications
Ordering Application Description
​Centricity ​Fluoxetine (Prozac)
​Cerner ​Fluoxetine Level (80228)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
​Serum Red Top Tube (RTT)​ 1 mL​ 0.5 mL​
Collection Processing
​Spin down and separate serum from cells within 2 hours of draw.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ ​ ​ Refrigerated (preferred)​ 28 days​
Frozen ​ 28 days​
Ambient 72 hours​
Rejection Criteria
​Serum gel tube
Interference

​Specimens that are obtained from gel tubes or anticoagulate collections can cause assay interference.

Useful For
​Monitoring serum concentration of fluoxetine during therapy
 
Evaluating potential toxicity
 
Evaluating patient compliance
Reference Range Information
Fluoxetine + Norfluoxetine: 120-500 ng/mL
Interpretation
​Most individuals display optimal response to fluoxetine when combined serum levels of fluoxetine and norfluoxetine are between 120 and 300 ng/mL. Some individuals may respond well outside of this range or may display toxicity within the therapeutic range, thus interpretation should include clinical evaluation. A toxic range has not been well established.
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories
Wednesday
1-8 days
Liquid Chromatography- Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80299
For most current information refer to the Marshfield Laboratory online reference manual.