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].

Absorption, Distribution and Excretion
The oral bioavailability of fluoxetine is <90% as a result of hepatic first pass metabolism. In a bioequivalence study, the Cmax of fluoxetine 20 mg for the established reference formulation was 11.754 ng/mL while the Cmax for the proposed generic formulation was 11.786 ng/ml. Fluoxetine is very lipophilic and highly plasma protein bound, allowing the drug and it's active metabolite, norfluoxetine, to be distributed to the brain.
Fluoxetine is primarily eliminated in the urine.
The volume of distribution of fluoxetine and it's metabolite varies between 20 to 42 L/kg.
The clearance value of fluoxetine in healthy patients is reported to be 9.6 ml/min/kg.

---

Metabolism / Metabolites
Fluoxetine is metabolized to norfluoxetine by CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A5 upon ingestion. Although all of the mentioned enzymes contribute to N-demethylation of fluoxetine, CYP2D6, CYP2C9 and CYP3A4 appear to be the major contributing enzymes for phase I metabolism. In addition, there is evidence to suggest that CYP2C19 and CYP3A4 mediate O-dealkylation of fluoxetine and norfluoxetine to produce para-trifluoromethylphenol which is subsequently metabolized to hippuric acid. Both fluoxetine and norfluoxetine undergo glucuronidation to facilitate excretion. Notably, both the parent drug and active metabolite inhibit CYP2D6 isozymes, and as a result patients who are being treated with fluoxetine are susceptible to drug interactions.
Fluoxetine has known human metabolites that include Norfluoxetine, p-Trifluoromethyl phenol, and (2S,3S,4S,5R)-3,4,5-trihydroxy-6-[methyl-[3-phenyl-3-[4-(trifluoromethyl)phenoxy]propyl]amino]oxane-2-carboxylic acid.
Limited data from animal studies suggest that fluoxetine may undergo first-pass metabolism may occur via the liver and/or lungs. Fluoxetine appears to be extensively metabolized, likely in the liver, to norfluoxetine and other metabolites. Norfluoxetine, the principal active metabolite, is formed via N-demethylation of fluoxetine. Norfluoxetine appears to be comparable pharmacologic potency as fluoxetine. Fluoxetine and norfluoxetine both undergo phase II glucuronidation reactions in the liver. It is also thought that fluoxetine and norfluoxetine undergo O-dealkylation to form p-trifluoromethylphenol, which is then subsequently metabolized to hippuric acid.
Route of Elimination: The primary route of elimination appears to be hepatic metabolism to inactive metabolites excreted by the kidney. The S-enantiomer is eliminated more slowly and is the predominant enantiomer present at steady state.
Half Life: 1-3 days [acute administration];
4-6 days [chronic administration];
4-16 days [norfluoxetine, acute and chronic administration].

---

Biological Half-Life
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. Further, the elimination half life of it's active metabolite, norfluoxetine, ranges from 4-16 days after both acute and chronic administration. The half-life of fluoxetine should be considered when switching patients from fluoxetine to another antidepressant since marked accumulation occurs after chronic use. Fluoxetine's long half-life may even be beneficial when discontinuing the drug since the risk of withdrawal is minimized.

Toxicity Summary
Fluoxetine is a cholinesterase or acetylcholinesterase (AChE) inhibitor. A cholinesterase inhibitor (or 'anticholinesterase') suppresses the action of acetylcholinesterase. Because of its essential function, chemicals that interfere with the action of acetylcholinesterase are potent neurotoxins, causing excessive salivation and eye-watering in low doses, followed by muscle spasms and ultimately death. Nerve gases and many substances used in insecticides have been shown to act by binding a serine in the active site of acetylcholine esterase, inhibiting the enzyme completely. Acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax. The result of acetylcholine esterase inhibition is that acetylcholine builds up and continues to act so that any nerve impulses are continually transmitted and muscle contractions do not stop. Among the most common acetylcholinesterase inhibitors are phosphorus-based compounds, which are designed to bind to the active site of the enzyme. The structural requirements are a phosphorus atom bearing two lipophilic groups, a leaving group (such as a halide or thiocyanate), and a terminal oxygen.

---

Toxicity Data
LD₅₀=284mg/kg (orally in 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
Fluoxetine blocks the serotonin reuptake transporter in the presynaptic terminal, which ultimately results in sustained levels of 5-hydroxytryptamine (5-HT) in certain brain areas. However, fluoxetine binds with relatively poor affinity to 5-HT, dopaminergic, adrenergic, cholinergic, muscarinic, and histamine receptors which explains why it has a far more desirable adverse effect profile compared to earlier developed classes of antidepressants such as tricyclic antidepressants.

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.

---

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.

---

View More

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.

---

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.

---

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