Fluoxetine: Drug Uses, Dosage, And Side Effects

Fluoxetine: Drug Uses, Dosage, And Side Effects

What Is Fluoxetine

Fluoxetine is a medicine in a class called SSRIs or selective serotonin reuptake inhibitors fluoxetine increases the amount of the neurotransmitter serotonin in the synapse by inhibiting its reuptake into the presynaptic neuron under the theory that many forms of depression are related to a lack of serotonin. Fluoxetine has active metabolites with half-lives of a week or more. 

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Common Uses of Fluoxetine

  •  To treat OCD
  •  To treat depression
  •  To treat bulimia
  • disorder 
  •  To treat the premenstrual dysphoric disorder 
  •  To treat dysmorphic 
  •  To treat fibromyalgia 
  •  To treat anxiety 
  •  To treat PTSD 
  •  To treat premature ejaculation 
  •  To treat social anxiety 
  •  For many other conditions also

How fluoxetine work

Chemical neurotransmission at the synapse involves the release from the presynaptic neuron of a transmitter substance, which then begins the process of affecting by binding to receptors. One issue, though, is that the synaptic supplies of the transmitter substance then needs to be removed so that its action does not build up to be too strong, or to continue too long.

This is accomplished by a breakdown by enzymes, diffusion out of the synapse, and by reuptake of the transmitter into the presynaptic neuron by reuptake pumps. one of the theories of the genesis of depression is that it involves relatively low levels of serotonin and norepinephrine.

The SSRIs, like the fluoxetine, work by raising serotonin levels by disabling the presynaptic uptake pumps, preventing them from removing serotonin from the synapse. Unlike the TCAs, however, the SSRIs have virtually no effect on norepinephrine reuptake, and minimal affinity for cholinergic, histaminic or alpha-adrenergic receptors—hence the word ‘selective’ in their name.

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Most common side effects of fluoxetine?

  • Sleepiness
  • Sexual dysfunction 
  • Drowsiness
  • Seizure
  • Weight gain
  •  Sexual difficulties, 
  •  Erectile dysfunction 
  • Weakness
  • Watery nasal discharge
  • sweating 
  • Sleep disturbance
  • Decreased appetite
  • Bad dream
  • Anxiety
  • Nervousness
  • Sore throat
  • Rash
  • Digestion problem
  • Flu

Serious side effects of fluoxetine?


A sense of aggravated and restless can occur with fluoxetine in the first week or two of treatment, particularly with fluoxetine. This symptoms often clear up on its own after 2-3 weeks.


Asthenia can be a difficult problem in long-term use. A person may feel a kind of apathy, a decrease in mental energy, or a sense of lacking emotional responsiveness.

Suicidal thoughts

This is quite rare, so for most people it is unlikely that starting your medication will make you feel suicidal.

Increased bleeding

There is a small risk of increased bleeding, which may be increased when also taking blood thinners, aspirin or NSAIDS. Fluoxetine can rarely cause a condition in which there is too little sodium in the blood; the risk for this is somewhat higher in the elderly and in persons taking diuretic medication

Serotonin syndrome

 Serotonin syndrome may involve confusion, increased blood pressure and pulse, sweating, shivering, muscle rigidity, diarrhea, agitation and other symptoms. Because of the potentially serious nature of serotonin syndrome, a person suspecting this may be occurring should seek medical attention at once

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Fluoxetine Alternatives

  • Paxil (Paroxetine)
  • Zoloft
  • Cymbalta (Duloxetine)
  •  Elavil (Amitriptyline)
  •  Nardil (Phenelzine)

Side effects of these drugs are very similar to fluoxetine

Warning & Precautions


Try to avoid Fluoxetine use during pregnancy or breastfeeding. Assessment of the risk versus benefits must be discussed with the patient.

Liver impairment: 

Fluoxetine should be avoided in patients with liver cirrhosis and liver insufficiency.

Alcohol abuse: 

Fluoxetine is not recommended in patient abusing alcohol.

Heart disease: 

Fluoxetine need to be used with caution in patients with cardiac impairment.

Kidney impairment:

 Fluoxetine should be used with caution in patients with renal impairment. A reduced dose is needed as fluoxetine and its metabolites may accumulate in the plasma to a greater extent.

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Fluoxetine use during pregnancy

Women with a history of mood disorder appear to be at risk for recurrence of depression during pregnancy, especially when antidepressants have been discontinued. Treatment of depression during pregnancy is related to the severity of illness, the past treatment response and the patient preferences.  

The information regarding the effects of antidepressants when are used during pregnancy is incomplete. The risks of  antidepressant use during pregnancy must be weight against the risks associated with untreated depression. 

In general there are several risks to consider with the use of antidepressants during pregnancy

  • Risk of organ malformation (teratogenesis)
  •  Risk of miscarriage
  •  Risk of neonatal toxicity (withdrwal symptoms)
  •  Risk of neonatal development of Persistant Pulmonary Hypertension of the Newborn (PPHN) 
  • Risk of long- term neurobehavioural effects of the child. 
  • Risk of suicide in the untreated pregnant women Risk of development of Post Partum depression

Fluoxetine interactions with other medicines

Most drug interactions of SSRIs reflect their inhibition of liver CYP450 enzymes. Fluoxetine, for instance, inhibits CYP2D6, which can lead to decreased metabolism (and hence increased blood concentrations) of some tricyclics, risperidone, trazodone, and bupropion. Fluvoxamine inhibits CYP3A4, leading to decreased metabolism of a variety of drugs. 

The SSRIs with the lowest risk of pharmacokinetic interactions are citalopram, escitalopram, and sertraline. The primary pharmacodynamic concern is the potential for serotonin syndrome when combined with MAOIs or other serotonergic drugs. it is essential to discontinue Fluoxetine for at least two weeks (at least 30 days in the case of fluoxetine) before starting an MAOI, or conversely stopping MAOIs for two weeks before starting Fluoxetine. 

It’s also important to remember that serotonergic drugs that might interact with Fluoxetine to produce serotonin syndrome can include non-psychiatric medicines. One commonly used drug that is serotonergic and is not often considered in this regard is the pain medicine tramadol, which should only be used with caution in combination with Fluoxetine.

Fluoxetine Overdose

Compared to the tricyclics, the SSRIs are relatively less toxic when taken alone in overdose, and amounts of up to 30 daily doses have been taken with minimal ill effects.

 Large amount of fluoxetine can result in sedation, gastrointestinal disturbance, tremors, or serotonin syndrome. Overdoses are often taken in combination with alcohol and other drugs, however, and in these conditions, can be medically serious or fatal.


The dosage is 10, 20 or 40 milligram usually dosage starts from around 20 milligrams a day for most adults the max dose is 80 milligrams a day rarely do people exceed 40 milligrams a day very very rare. It's usually taken in the morning with or without food a lot of people do take it first thing in the morning. 

FDA has recommended that it not be prescribed in doses over 40 mg per day.


What time of day should I take Fluoxetine?. 

Fluoxetine is usually taken in the morning with or without food a lot of People do take it first thing in the morning 

Is fluoxetine and Prozac the same?

Prozac is the brand name for fluoxetine. fluoxetine increases the amount of the neurotransmitter serotonin in the synapse by inhibiting its reuptake into the presynaptic neuron.

How long does fluoxetine take to work

Fluoxetine take a couple weeks to start noticing a difference.Typically by 4-6 weeks though you should know how well this medication is going to work for you.

Does fluoxetine cause weight gain?

Fluoxetine generally known for causing large weight loss for that matter weight gainers reported in less than 1% so weight loss is more likely with this medication 


Fluoxetine: A review on evidence based medicine. (n.d.). PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC356924/

Long-term outcomes of developmental exposure to fluoxetine: A review of the animal literature. (n.d.). Karger Publishers. https://www.karger.com/Article/FullText/355709

Fluoxetine. (n.d.). ScienceDirect.com | Science, health and medical journals, full text articles and books. https://www.sciencedirect.com/topics/neuroscience/fluoxetine

Fluoxetine overdose-induced seizure. (n.d.). PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2672257/