Side effects

Fluoxetine is characterized by a broad spectrum of possible side effects. However, compared to the tricyclic antidepressants that have been prescribed for years, Fluoxetine is better tolerated and (severe) side effects occur significantly less frequently. The majority of side effects during treatment with Fluoxetine occur only rarely (1 to 10 out of 10,000 patients).

They occur mainly at the beginning of treatment and decrease over time. They should therefore not be a reason for premature discontinuation of therapy. Very often nausea and vomiting occur during therapy with Fluoxetine.

These symptoms are often accompanied by insomnia, fatigue, loss of appetite, anxiety and nervousness. In addition, sexual dysfunction can occur with a loss of sexual desire (libido). Effects on weight are also possible.

While some patients may experience an increase in weight, a slight weight loss is also possible. A dreaded side effect of treatment with fluoxetine is serotonin syndrome. It occurs when the serotonin levels are rapidly increased or overdosed due to the greatly increased serotonin levels.

It is often caused by a combination of several drugs that have an influence on serotonin levels. Typical symptoms are dizziness and clouding of consciousness. Involuntary twitching of the muscles, anxiety and a general feeling of illness are also frequently reported.

Symptoms of fatigue are particularly common at the beginning of treatment with fluoxetine. The severity of the symptoms varies from patient to patient and may also depend on the dosage. Patients often complain of a strong lack of drive during the day and often feel the need for a nap.

In rare cases, there may also be a slight clouding of consciousness and impaired concentration and thinking. These symptoms usually diminish as treatment progresses, as the drug develops its stimulating effect after a few days or weeks. In cases of very severe fatigue with clouding of consciousness, discontinuation of the medication can be discussed with the treating physician.

If necessary, a reduction of the dose can also lead to an alleviation of the symptoms. Since the various selective serotonin reuptake inhibitors (SSRIs) act very differently from patient to patient, a change to another preparation may also be indicated. Frequently, a therapy with fluoxetine also shows side effects in the gastrointestinal tract.

This is because serotonin is an important messenger substance of the intestinal nervous system (enteric nervous system). The administration of fluoxetine can disrupt this system in its function. Symptoms also occur mainly at the beginning of treatment and gradually subside after several weeks.

Patients often complain of nausea and vomiting. This is accompanied by a loss of appetite, which can lead to weight loss if high doses are administered. At the same time, diarrhoea and digestive disorders occur more frequently.

Another side effect that can occur during treatment with Fluoxetine is the loss of libido (sexual desire).Men are particularly affected by this. The origin of this sexual dysfunction is not yet fully understood. Even taking the medication for a few days can lead to the onset of the symptoms.

Often patients report a reduced or non-existent libido. In addition, there is difficulty in producing or maintaining an erection or sexual arousal. A permanent erection or premature orgasms are also possible.

In rare cases, patients report impotence. After stopping the medication, side effects may continue for months or years in some cases. In very rare cases a permanent sexual dysfunction is also reported.

After taking Fluoxetine tablets, the active ingredient is metabolised in the liver by specific enzymes. At the same time, fluoxetine is broken down by enzymes in the liver. Due to the heavy strain on the liver, damage to the liver tissue can occur.

Changes in liver values (GOT, GPT) often occur during therapy with fluoxetine. For this reason, liver function should be monitored regularly and the dose adjusted accordingly if liver function is impaired. While many patients complain of daily fatigue during therapy with fluoxetine, sleep disturbances during the night can also occur.

As studies have shown, this effect is due to an influence on melatonin synthesis (sleep hormone) in the central nervous system. In comparison to tricyclic antidepressants, which have a dampening and thus sleep-promoting effect, selective serotonin reuptake inhibitors (SSRIs) are characterized by a drive-enhancing effect. Although patients often report severe fatigue, they are unable to sleep for long.

At the same time, these short sleep episodes are often accompanied by nightmares. Another frequent side effect is sensory disturbances (paresthesias) in the skin area with severe itching. Depending on the patient, this itching can be pronounced to varying degrees.

It is often accompanied by rashes of the skin with formation of small blisters. If the symptoms are unclear or persist for a longer period of time, a doctor should be consulted in any case and the further procedure should be discussed. If necessary, an intolerance (allergy) to fluoxetine or other ingredients of the preparation may also be present.

Many of the antidepressants prescribed today have an effect on patients’ weight. An increase in weight often has a negative effect on the further success of treatment for depression. While the tricyclic antidepressants (amitriptyline, clomipramine, nortriptyline) and mirtazapine lead to weight gain through an increase in appetite, treatment with fluoxetine can also result in a reduction in weight.

Some patients report a weight loss of several kilograms per month. This is mainly due to a reduced appetite in high-dose therapy. At the same time, dry mouth and an increasing change in taste can also occur as side effects during treatment with Fluoxetine, which increases the loss of appetite.