Yale New Haven Hospital

Department of Laboratory Medicine
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Fluoxetine and metabolite

Lab Section: 

Sendout Reference


Lab Location: 


Reference Lab: 



Test ID: 




Norfluoxetine/Fluoxetine, Blood Prozac, Blood


Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)




2 weeks

Specimen Requirements: 

Collection: 3.0 mL Blood in a Red Top Tube.
Pediatric volume: 1 mL.
Serum; Plain, red-top tube(s). Spin down and separate serum from cells within 2 hours of draw.
Transport: Store and ship refrigerated.
Unacceptable conditions: Serum gel tube; Specimens other than serum; Gross hemolysis; Gross lipemia
Stability: Refrigerated (preferred): 14 days; Frozen: 180 days; Ambient: 72 hours



Clinical Indications: Fluoxetine is a selective serotonin reuptake inhibitor approved for treatment of bulimia, obsessive-compulsive behavior, panic, 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 (120-300 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 CYP2D6, 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 Interval: 

See patient report or consult reference laboratory website.


CPT Code(s): 


Last Changed: 

8/29/2017 2:38:45

Last Reviewed: 

8/29/2017 2:38:45