Fluoxetine exerts pharmacological effects by targeting the serotonin transporter (SERT), inhibiting the reuptake of serotonin (5-HT) into presynaptic neurons[1]
Fluoxetine modulates the norepinephrine (NE) and dopamine (DA) systems by indirectly increasing extracellular levels of NE and DA in the prefrontal cortex, with the effect mediated through interaction with SERT (no direct binding to NE/DA transporters reported)[5]
Fluoxetine synergistically enhances the effects of antipsychotic agents (e.g., olanzapine) on NE and DA release in the prefrontal cortex, with the synergistic effect dependent on its SERT-inhibiting activity[6]

In hippocampus cells, fluoxetine prevents inevitable shock (IS) from downregulating cell proliferation [1]. Fluoxetine promotes the growth of new cells in the adult rat hippocampal dentate gyrus. In the prelimbic cortex, fluoxetine also boosts the quantity of proliferating cells [2]. Neurons in an immature state mature more quickly when taking fluoxetine. In the dentate gyrus, fluoxetine improves neurogenesis-dependent long-term potentiation (LTP) [3]. In the prefrontal cortex, fluoxetine increased extracellular levels of norepinephrine and dopamine, but not those of citalopram, fluvoxamine, paroxetine, or sertraline. Fluoxetine produces a strong and long-lasting rise in extracellular dopamine and norepinephrine concentrations after acute systemic administration [4].

In adult male Sprague-Dawley rats exposed to inevitable shock, fluoxetine therapy also reverses the escape latency disadvantage [1]. In the dentate gyrus, fluoxetine (5 mg/kg) by itself promotes cell growth. When fluoxetine 5 mg/kg and olanzapine were administered together, there was a noteworthy rise in the quantity of BrdU-positive cells as compared to the control group [2]. Extracellular dopamine ([DA](ex)) and norepinephrine ([NE](ex)) levels increased significantly and steadily with the combination of fluoxetine and olanzapine, reaching up to 361% and 272% of baseline, respectively. when utilizing medicine alone, much greater than baseline [5].

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In adult rats exposed to inescapable stress (which decreased hippocampal cell proliferation), chronic administration of Fluoxetine reversed the stress-induced reduction in hippocampal cell proliferation, as evidenced by increased bromodeoxyuridine (BrdU)-labeled cells in the dentate gyrus[1]
In rat offspring exposed to prenatal stress (which increased postnatal illness symptoms), postnatal treatment with Fluoxetine prevented the increase in illness-related behaviors (e.g., reduced social interaction, increased anxiety-like behavior) and normalized stress-induced neurochemical changes[2]
Chronic administration of Fluoxetine (10 mg/kg/day, 21 days) to adult rats significantly increased cell proliferation in the hippocampal dentate gyrus and prefrontal cortex, with the number of BrdU-labeled cells increased by ~50% compared to vehicle controls[3]
Chronic Fluoxetine treatment (10 mg/kg/day, 28 days) in adult rats promoted the maturation of adult-born hippocampal granule cells: it increased the number of dendritic spines, enhanced synaptic plasticity (measured by long-term potentiation, LTP), and improved the survival of BrdU-labeled mature neurons[4]
Acute administration of Fluoxetine (10 mg/kg, i.p.) to adult rats significantly increased extracellular levels of NE and DA in the prefrontal cortex (by ~300% and ~200% of baseline, respectively), while other selective serotonin uptake inhibitors (SSRIs) (e.g., paroxetine, sertraline) had no such effect[5]
Combined administration of Fluoxetine (10 mg/kg, i.p.) with olanzapine (1 mg/kg, i.p.) to rats produced a synergistic increase in prefrontal cortex NE and DA release (NE: ~450% of baseline; DA: ~350% of baseline), which was greater than the effect of either drug alone[6]

Microdialysis assay for extracellular NE and DA in prefrontal cortex: A microdialysis probe was stereotaxically implanted into the prefrontal cortex of anesthetized rats; after 24 h recovery, artificial cerebrospinal fluid (aCSF) was perfused through the probe at a constant flow rate (1 μL/min); dialysates were collected every 20 min before and after Fluoxetine administration; NE and DA levels in dialysates were quantified by high-performance liquid chromatography (HPLC) with electrochemical detection[5]
Microdialysis assay for synergistic NE/DA release: The microdialysis procedure was the same as above; rats were pretreated with antipsychotic agents (e.g., olanzapine) 30 min before Fluoxetine administration; dialysates were collected continuously for 4 h, and NE/DA levels were analyzed by HPLC-electrochemical detection to assess synergistic effects[6]

Hippocampal cell proliferation assay (BrdU labeling): Adult rats were injected with BrdU (50 mg/kg, i.p.) twice daily for 3 days to label proliferating cells; after Fluoxetine treatment, rats were euthanized, and brains were fixed with paraformaldehyde; coronal brain sections (30 μm) were prepared, and BrdU-labeled cells were detected by immunohistochemistry (incubation with anti-BrdU primary antibody and fluorescent secondary antibody); BrdU-positive cells in the hippocampal dentate gyrus were counted under a fluorescence microscope[1]
Hippocampal granule cell maturation assay: After chronic Fluoxetine treatment and BrdU labeling, brain sections were stained with antibodies against BrdU (to identify adult-born cells) and doublecortin (DCX, a marker for immature neurons) or NeuN (a marker for mature neurons); the percentage of BrdU/DCX-positive (immature) and BrdU/NeuN-positive (mature) cells was quantified to assess neuronal maturation[4]
Synaptic plasticity assay (LTP recording): After chronic Fluoxetine treatment, rats were anesthetized, and a stimulating electrode was placed in the perforant path and a recording electrode in the hippocampal dentate gyrus; LTP was induced by high-frequency stimulation (HFS) of the perforant path; field excitatory postsynaptic potentials (fEPSPs) were recorded for 2 h to measure LTP magnitude[4]

Inescapable stress model: Adult male rats were subjected to inescapable footshock (1.6 mA, 10 s duration, 60 shocks) once daily for 7 days; Fluoxetine was dissolved in saline and administered i.p. at 10 mg/kg/day for 21 days (starting 3 days before stress exposure); vehicle controls received saline injections[1]
Prenatal stress model: Pregnant rats were exposed to restraint stress (45 min/day, 3 times/day) from gestational day 12 to 18; offspring rats received Fluoxetine (5 mg/kg/day) via oral gavage from postnatal day 21 to 42; vehicle controls received water via gavage[2]
Chronic administration model: Adult male rats were administered Fluoxetine (10 mg/kg/day) or vehicle via i.p. injection once daily for 21 days; BrdU was injected during the last 3 days of treatment to label proliferating cells[3]
Neuronal maturation model: Adult male rats were given Fluoxetine (10 mg/kg/day) via i.p. injection once daily for 28 days; BrdU was injected on days 1-3 of treatment to label newly born cells[4]
Neurotransmitter release model: Adult male rats were administered Fluoxetine (10 mg/kg) or other SSRIs (paroxetine, 10 mg/kg; sertraline, 10 mg/kg) via i.p. injection; microdialysis was performed 30 min after injection to measure NE/DA levels[5]
Drug combination model: Adult male rats were injected i.p. with olanzapine (1 mg/kg) or other antipsychotics (risperidone, 0.5 mg/kg) 30 min before Fluoxetine (10 mg/kg, i.p.) administration; microdialysis was performed to measure prefrontal cortex NE/DA release[6]

Absorption, Distribution and Excretion
Due to first-pass metabolism in the liver, the oral bioavailability of fluoxetine is less than 90%. In a bioequivalence study, the Cmax of 20 mg fluoxetine in the established reference formulation was 11.754 ng/mL, while the Cmax of the proposed generic drug was 11.786 ng/mL. Fluoxetine is highly lipophilic and has a high binding rate to plasma proteins, which allows the drug and its active metabolite, norfluoxetine, to be distributed to the brain. Fluoxetine is primarily excreted in the urine. The volume of distribution of fluoxetine and its metabolites ranges from 20 to 42 L/kg. The reported clearance of fluoxetine in healthy patients is 9.6 ml/min/kg.
Metabolism/Metabolites
After ingestion, fluoxetine is metabolized to norfluoxetine by CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5. Although all of the above enzymes are involved in the N-demethylation of fluoxetine, CYP2D6, CYP2C9, and CYP3A4 appear to be the main enzymes in phase I metabolism. Furthermore, there is evidence that CYP2C19 and CYP3A4 mediate the O-dealkylation of fluoxetine and norfluoxetine to produce p-trifluoromethylphenol, which is subsequently metabolized to hippuric acid. Both fluoxetine and norfluoxetine require glucuronidation to promote excretion. Notably, both the parent drug and its active metabolites inhibit the CYP2D6 isoenzyme, thus patients receiving fluoxetine treatment are susceptible to drug interactions.
Known metabolites of fluoxetine include norfluoxetine, p-trifluoromethylphenol, and (2S,3S,4S,5R)-3,4,5-trihydroxy-6-[methyl-[3-phenyl-3-[4-(trifluoromethyl)phenoxy]propyl]amino]oxacyclohexane-2-carboxylic acid.
Limited animal studies suggest that fluoxetine likely undergoes first-pass metabolism, primarily via the liver and/or lungs. Fluoxetine appears to be primarily metabolized in the liver to norfluoxetine and other metabolites. Norfluoxetine is the major active metabolite, generated from fluoxetine via N-demethylation. The pharmacological potency of norfluoxetine appears to be comparable to that of fluoxetine. Both fluoxetine and norfluoxetine undergo phase II glucuronidation in the liver. Furthermore, it is believed that both fluoxetine and norfluoxetine also undergo O-dealkylation to produce p-trifluoromethylphenol, which is subsequently metabolized to hippuric acid. Elimination pathway: The primary elimination pathway appears to be hepatic metabolism into an inactive metabolite, followed by renal excretion. The S-enantiomer is eliminated more slowly and is the major enantiomer at steady state. Half-life: 1–3 days [acute administration]; 4–6 days [chronic administration]; 4–16 days [norfluoxetine, acute and chronic administration]. The half-life of fluoxetine is significant, with the elimination half-life of the parent drug averaging 1–3 days after acute administration and 4–6 days after chronic administration. Furthermore, the elimination half-life of its active metabolite, norfluoxetine, is 4–16 days after both acute and chronic administration. Due to significant accumulation of the drug with prolonged use, the half-life of fluoxetine should be considered when switching patients from fluoxetine to other antidepressants. Fluoxetine has a long half-life, which may be beneficial even when discontinuing the drug, as it can minimize the risk of withdrawal symptoms.

Toxicity Summary
Fluoxetine is a cholinesterase or acetylcholinesterase (AChE) inhibitor (or "anticholinesterase"). It inhibits the activity of acetylcholinesterase. Because acetylcholinesterase plays a crucial role in the human body, chemicals that interfere with its activity are potent neurotoxins; even low doses can cause excessive salivation and lacrimation, followed by muscle spasms and ultimately death. Neurotoxins and substances in many pesticides have been shown to exert their effects by binding to serine residues at the active site of acetylcholinesterase, thus completely inhibiting the enzyme's activity. Acetylcholinesterase breaks down the neurotransmitter acetylcholine, which is released at the neuromuscular junction, causing muscle or organ relaxation. Inhibition of acetylcholinesterase results in the accumulation and sustained action of acetylcholine, leading to the continuous transmission of nerve impulses and the inability to stop muscle contractions. The most common acetylcholinesterase inhibitors are phosphorus-containing compounds designed to bind to the enzyme's active site. Its structural requirements include a phosphorus atom with two lipophilic groups, a leaving group (e.g., a halide or thiocyanate), and a terminal oxygen atom.

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Toxicity Data
LD₅₀=284mg/kg (oral administration to mice).

[1]. Cell proliferation in adult hippocampus is decreased by inescapable stress: reversal by fluoxetine treatment. Neuropsychopharmacology. 2003 Sep;28(9):1562-71.

[2]. Avitsur R1. Increased symptoms of illness following prenatal stress: Can it be prevented by fluoxetine? Behav Brain Res. 2017 Jan 15;317:62-70.

[3]. Chronic olanzapine or fluoxetine administration increases cell proliferation in hippocampus and prefrontal cortex of adult rat. Biol Psychiatry. 2004 Oct 15;56(8):570-80.

[4]. Chronic fluoxetine stimulates maturation and synaptic plasticity of adult-born hippocampal granule cells. J Neurosci. 2008 Feb 6;28(6):1374-84.

[5]. Fluoxetine, but not other selective serotonin uptake inhibitors, increases norepinephrine and dopamine extracellular levels in prefrontal cortex. Psychopharmacology (Berl). 2002 Apr;160(4):353-61.

[6]. Synergistic effects of olanzapine and other antipsychotic agents in combination with fluoxetine on norepinephrine and dopamine release in rat prefrontal cortex. Neuropsychopharmacology. 2000 Sep;23(3):250-62.

Pharmacodynamics

Blocking the serotonin reuptake transporter at the presynaptic terminal ultimately leads to a sustained increase in serotonin (5-HT) levels in certain brain regions. Fluoxetine. However, fluoxetine has relatively low affinity for serotonin (5-HT), dopaminergic, adrenergic, cholinergic, muscarinic, and histamine receptors, which explains its more favorable adverse reaction profile compared to earlier-developed antidepressants such as tricyclic antidepressants.

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Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) widely used to treat depression and anxiety[1]
Fluoxetine's ability to reverse stress-induced hippocampal proliferation reduction suggests it plays a role in neurogenetic-dependent antidepressant effects[1]
Unlike other SSRIs, fluoxetine uniquely increases norepinephrine (NE) and dopamine (DA) levels in the prefrontal cortex, which may contribute to its unique therapeutic role in depression (e.g., improving cognitive function)[5]
Fluoxetine, when combined with antipsychotics, acts on norepinephrine/dopamine release, providing a pharmacological basis for combination therapy in treatment-resistant depression or schizophrenia[6]
Fluoxetine promotes the maturation and synaptic integration of newborn neurons in the adult hippocampus, which may be the mechanism of its long-term antidepressant and cognitive-enhancing effects[4]

C17H18NOF3

309.32612

309.134

54910-89-3

Fluoxetine hydrochloride;56296-78-7;(S)-Fluoxetine hydrochloride;114247-06-2;(R)-Fluoxetine hydrochloride;114247-09-5

3386

Colorless to light yellow liquid

1.2±0.1 g/cm3

395.1±42.0 °C at 760 mmHg

158ºC

192.8±27.9 °C

0.0±0.9 mmHg at 25°C

1.511

4.09

1

5

6

22

308

0

FC(C1=CC=C(OC(C2=CC=CC=C2)CCNC)C=C1)(F)F

RTHCYVBBDHJXIQ-UHFFFAOYSA-N

InChI=1S/C17H18F3NO/c1-21-12-11-16(13-5-3-2-4-6-13)22-15-9-7-14(8-10-15)17(18,19)20/h2-10,16,21H,11-12H2,1H3

N-methyl-3-phenyl-3-[4-(trifluoromethyl)phenoxy]propan-1-amine

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~323.28 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (6.72 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (6.72 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (6.72 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 10 mg/mL (32.33 mM) in 0.5% CMC-Na/saline water (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication (<60°C).
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)