Fluoxetine: what is it for? Does it have side effects?

Thousands of people in Brazil and in the world undergo treatment with medications from the psychiatric segment, for the most diverse conditions ( depression , anxiety , panic syndrome, etc.).

Among these drugs, there are those that rely on Fluoxetine as an active ingredient. So, now see how this drug substance works, for which cases it is indicated and other information about its action in the body:


What is Fluoxetine?

Fluoxetine, or Fluoxetine Hydrochloride, is a drug substance that acts as an active ingredient in several medications. These are aimed at treating disorders such as depression and bulimia nervosa.

This substance is part of the Selective Serotonin Recapture Inhibitors (SSRIs), the pharmacological class of antidepressants that is most prescribed worldwide. This is because they are better tolerated by the body, presenting low toxicity and minimal side effects.

Despite including other medications, such as paroxetine, sertraline and fluvoxamine, it is important to note that this does not mean that they have the same AP (active ingredient). That is, they do not act in the same way.

In general, Fluoxetine acts on the reception of serotonin , preventing it from being recaptured and being able to perform its signaling function, thus controlling the symptoms of some psychological disorders – such as depression or OCD .

This is because serotonin , or 5-hydroxytryptamine (5-HT), is the hormone responsible for the general modulation of psychic activity. Thus, it impacts almost all brain activities. For example, it works by regulating mood, sleep, appetite, perception of pain, etc.

As for the availability of Fluoxetine, the drugs that rely on this substance as a drug (active ingredient) are sold in tablets / capsules or drops, for oral administration.

It is also worth noting that Fluoxetine is registered with ANVISA, classified in the category of antidepressant drugs. Thus, it can be guaranteed that this medication has its safety and efficacy attested from tests.

What is Fluoxetine for?

Fluoxetine is, according to the package insert, recommended for the treatment of depression (associated or not with anxiety), bulimia nervosa, obsessive-compulsive disorder (OCD) and premenstrual dysphoric disorder (severe form of premenstrual syndrome, including physical and behavioral symptoms) – including PMS, irritability and dysphoria.

So, in general, the problems treated by Fluoxetine are related to changes in mood (different from normal changes, which have an apparent cause), physical or emotional sensitivity, hormonal changes, among other factors.

So, even if you have a diagnosis, or symptoms, of one or more of the aforementioned disorders, you should never use Fluoxetine (or any other medication) independently. It is always necessary to follow and count on medical assistance.

Is fluoxetine for anxiety?

As mentioned, according to the instructions on the label, Fluoxetine can be recommended in cases of depression associated (or not) with anxiety.

However, the package insert does not provide recommendations for the use of this medication for the treatment of anxiety disorder only. Despite this, many professionals prescribe the drug for these cases, indicating that it is effective.

This is because, in general, many disorders originate from anxiety, so that it triggers other problems or is associated with them.

According to the pharmaceutical company Francielle Mathias, “antidepressants in general, including Fluoxetine, increase the levels of neurotransmitters involved with our emotions and well-being” and, to some degree, this interferes with anxiety, reducing or controlling your symptoms – which can vary according to the patient’s history.

In this sense, the pharmacist explains that “therefore, doctors can prescribe an antidepressant to treat anxiety. However, it can also be a side effect of the medication, since by changing the levels of transmitters, the body can react in a way that is not entirely predictable. ”

Thus, until the medication reaches its maximum effect, this type of reaction is possible. That is, the anxious sensation can be aggravated at the beginning of the treatment.

It is necessary to consider that sometimes the side effect of increased anxiety appears and remains – it is necessary to change the medicine, but sometimes it disappears and the patient adapts.

You can talk to the doctor responsible for your case, so that he / she can prescribe the correct treatment for you. In cases of other doubts, it is also possible to consult the Fluoxetine leaflet .

What does Fluoxetine do?

People who suffer from psychological disorders (such as depression) have low concentrations of serotonin. Then, from the use of SSRI-type medications, such as Fluoxetine, the concentrations of this hormone increase.

This is due to the high affinity for their selective transporters. However, initially a high catch still occurs, keeping the serotonin level low. From the continuous and prolonged use, the reuptake of it becomes less and its concentration increases.

It is when the effects of treatment begin to be better perceived, such as the regulation of mood, sleep, appetite, intellectual functions, etc.,

It is worth noting that the therapeutic response is, in general, observed a few weeks after the start of treatment. However, if the person does not show improvement in symptoms, it is normal that the doctor needs to evaluate and readjust the dose used – or even change the medication.

Is there Fluoxetine in drops?

-Yeah . Among the drugs that contain Fluoxetine as an active ingredient, there are some versions in drops, such as:

  • Verotina Gotas ;
  • Daforin ;
  • Fluoxetine Hydrochloride Oral Solution Medley ;
  • Depress.

It is important to always talk to the doctor responsible for your treatment, he / she will be able to advise on the use of medication in drops or pills and how to do it safely.

What milligram is available?

Fluoxetine is available in doses of 20mg (tablet) and 20mg / L (drops).

However, it is worth noting that the dosage recommended by the doctor may be greater than that, being necessary to ingest more than one pill or increase the amount of drops in the dose.

In this case, the professional will always analyze the patient’s condition and follow the indications recommended by the package insert.

Therefore, changes should not be made regardless of the dose administered, so always follow medical guidelines . The following topic can help to better understand how to take the medication according to the package insert (which does not dispense with medical help):

How to take according to the package insert?

Medicines that have Fluoxetine as an active ingredient are available in two versions, tablets / capsules or in drops.

It is important to highlight that, regardless of the version, there is no pre-designated treatment time. That is, this varies according to each person, which reinforces the role of the responsible physician.

In addition, treatment is not stopped immediately, but gradually according to the recommendations of the specialist.

Recalling, still, that there is a possibility that the problem will reoccur and it is necessary to resume treatment – you should seek medical help already in the onset of the first symptoms.

Now, see how to take according to the package insert in each case (tablets or drops):

Pills or capsules

According to the instructions on the package insert, tablets or capsules are always taken orally and can be taken regardless of meals – however, if taken with food it can reduce the risk of some side effects, such as nausea.

The schedule for administering the medication should be aligned with the doctor responsible for its treatment.

As for the dose, it varies according to the person’s case, considering that Fluoxetine can be used to treat different disorders: depression, bulimia, OCD, etc.

In general, the package insert is that the minimum dose is 20 mg daily and the maximum dose is 80 mg daily – considering that doses larger than this have not been sufficiently evaluated.


The medication in drops is also administered orally, and can be taken regardless of meals – following the schedule indicated by the doctor responsible for your treatment.

According to the package insert, the dropper bottle must be kept in a fully upright position for its correct use. The drops of the medicine should be dripped into a glass of water and, before drinking, it is necessary to mix well with a spoon.

Regarding the dose, it is important to know that 1 milliliter (mL) corresponds to 20mg of Fluoxetine. Thus, 20 drops correspond to 20mg of the substance – minimum daily dose.

Like the pill medicine, the maximum dose should not exceed 80mg daily.

When is the best time to take Fluoxetine?

The Fluoxetine package insert does not indicate the time at which the medication should be taken. Therefore, always follow the doctor’s guidance and make observations regarding the effect of the medicine.

They are necessary because some people may feel drowsy with the medication, so it would be better to take them at night.

In contrast, many patients feel more active and prefer to administer the medicine in the morning.

Thus, time adjustments during treatment may be necessary. However, they should never be done independently, but always with the monitoring and medical indication.

In addition, it is worth noting that whatever the chosen time, medication should be administered according to medical advice.

When does Fluoxetine start taking effect?

According to the instructions on the label, Fluoxetine reaches its maximum concentration in the body within 6 to 8 hours after ingestion. However, daily administration is necessary to achieve the desired therapeutic effects – the effects can be evident between 2 and 6 weeks of use.

That is, to fully feel the effects of the medication, it takes approximately 1 month of use, which may vary more or less according to each person.

It is also worth mentioning that Fluoxetine is metabolized in the liver, becoming norfluoxetine and other metabolites (product of the metabolism of a certain molecule or substance), which are excreted in the urine.

The elimination of Fluoxetine occurs between 4 to 6 days after ingestion, whereas its active metabolite can take from 4 to 16 days to be completely excreted.

What are the side effects of Fluoxetine?

Like any drug substance, Fluoxetine can cause side effects in people who use it. Remembering that it is a relative issue, because in some cases there is no effect and in others more than one is manifested.

It is worth mentioning that the therapeutic class of Fluoxetine (selective serotonin reuptake inhibitors) has the least intense side effects.

Despite this, adverse reactions can occur. In this sense, the package insert indicates the following as very common (they occur in more than 10% of cases):

  • Diarrhea;
  • Sickness;
  • Fatigue (tiredness), dizziness or decreased muscle strength;
  • Headache;
  • Insomnia;
  • Flu-like syndrome – including fever, cough or sore throat;
  • Pharyngitis (inflammation of the pharynx);
  • Sinusitis (inflammation of the sinuses).

There are also common side effects (between 1% and 10% of cases):

  • Palpitations (sensation of heart beat faster than normal);
  • Blurred vision;
  • Dry mouth;
  • Dyspepsia (gastrointestinal indisposition);
  • Vomiting;
  • Chills;
  • Feeling of agitation, nervousness, restlessness and / or tension;
  • Weight reduction;
  • Decreased appetite;
  • Attention disorder;
  • Vertigo (false feeling of movement);
  • Alteration of taste;
  • Sensation of slowness of movement and reasoning;
  • Somnolence;
  • Tremors;
  • Abnormal dreams (including nightmares);
  • Anxiety;
  • Decrease or loss of libido (sexual desire);
  • Urinating more frequently;
  • Ejaculation disorders or erectile dysfunction;
  • Gynecological bleeds;
  • Excessive sweat;
  • Skin disorders: hives (itchy skin rashes), flushing (redness of the skin) or just itching;
  • Sensation of heat by the body;
  • Emotional instability.

Does fluoxetine make you sleepy?

Among the side effects of using Fluoxetine is drowsiness. So in some cases, one can but feel more sleep than usual.

But, like any side effect, you need to talk to the doctor to make sure that the change is actually related to the use of the medication, or if it has another cause.

In addition, the package insert points to insomnia as a very common side effect. Thus, some patients may have the opposite effect: instead of feeling drowsy, they have greater difficulty sleeping.

Does fluoxetine get fat or lose weight?

Some adverse reactions to the use of Fluoxetine are associated with issues of the intestinal tract: such as vomiting, gastrointestinal upset, loss of appetite, etc.

Therefore, the combination of these factors can lead to weight loss in some cases. So, some people can lose weight during treatment with this substance.

But, when you notice any change for no apparent reason, both for weight gain and loss, it is essential to seek a specialist.

Remembering that, many times, people who suffer from emotional disorders can suffer from altered appetite and eating routines. That is, eat less or more than normal.

With the start of treatment, these changes can be controlled and there may be a dietary change capable of interfering with weight.

Can you drive on Fluoxetine?

Fluoxetine can interfere with the ability to judge, think and act – essential for driving vehicles or operating machines. So, until you are sure that the performance of these capabilities has not been affected, you should avoid these activities, as these practices would not be safe in the event of changes.

In any case, you should always do medical monitoring and follow the guidelines given by the professional, which will be provided based on your case.

Accepting the recommendations of the package leaflet and the doctor responsible for your case is essential to ensure the safety and efficacy of the treatment.

Price: what is the average value of Fluoxetine?

Fluoxetine is the active ingredient of different drugs, in generic, similar versions and in its reference form .

A reference drug is the one that originated the medication formula. When created, the developer laboratory is entitled to a patent period – which means that it will have exclusivity in the commercialization of this formula for a period of a few years.

After the patent period, the formula is made available and similar and generic drugs can be created.

Usually, this difference in versions changes the price * of the drug, in addition to issues such as box size and availability in your region. Then, see the comparison in the case of remedies that contain Fluoxetine as an active ingredient:

  • Prozac – reference medicine , available in boxes of 7, 14, 15 and 30 tablets. The price can vary between R $ 60 and R $ 260;
  • Fluoxetine Hydrochloride Cimed – generic medicine . The price of the box with 28 capsules is around R $ 30;
  • Daforin Tablet – similar medicine , available in a box with 30 or 60 tablets. The price can vary between R $ 48 and R $ 100.

* Prices consulted in April 2020. Prices may change.

Medicines for continuous use, such as those that rely on Fluoxetine, need even greater care during their administration. Therefore, always follow medical guidelines and carry out the necessary follow-up, in order to guarantee a safe and effective treatment.

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