How fluoxetine works
Fluoxetine is an active substance from the group of selective serotonin reuptake inhibitors (SSRIs) with antidepressant (mood-lifting) properties.
As an antidepressant, fluoxetine intervenes directly in brain metabolism. In the brain, messenger substances called neurotransmitters transmit signals between individual nerve cells: After being released from a nerve cell, the neurotransmitters dock onto binding sites (receptors) on the neighboring cell, thus transmitting a signal. To terminate the signal, the messenger substances are reabsorbed into the cell of origin.
The exact causes of depression are not yet known. However, it is known that at least one of the causes of depressive disorders can be a deficiency of the messenger substance serotonin (the so-called “happiness hormone”).
The desired antidepressant effect from fluoxetine occurs approximately one to two weeks after initiation of therapy.
Absorption, degradation and excretion
Fluoxetine is absorbed into the blood through the intestinal wall, where it reaches its maximum concentration about six hours after ingestion. Fluoxetine travels through the blood to the liver, where much of it is slowly metabolized, and to the brain, where it exerts its effects.
The blood level of the active ingredient drops by half after about two days if taken once, and by half after about four to six days if taken several times. This so-called “half-life” is very long compared to other antidepressant agents, which can have both advantages and disadvantages.
When is fluoxetine used?
The areas of use for fluoxetine include:
- Depressive disorders (episodes of major depression).
- Obsessive-compulsive disorder
- Bulimia (“binge eating disorder”)
In the latter case, the patient must also receive psychotherapeutic counseling. In most cases, such counseling is also useful in the other areas of application.
How fluoxetine is used
Fluoxetine is available for ingestion only, usually as a tablet or hard capsule, occasionally as a solution to drink or tablets to prepare a drinking solution.
In most cases, once-daily dosing in the morning is recommended. In cases of high dosages or gastric intolerance, the daily dose may be divided and taken throughout the day.
It can be taken with or between meals, as this does not affect the absorption of the active ingredient. The individually required dosage is determined by the doctor.
What are the side effects of fluoxetine?
Because the antidepressant has a particularly long duration of action and residence time in the body, special attention must be paid to side effects during therapy. This is because the effect of fluoxetine can last for several days even after the drug has been discontinued.
In one in ten to one in a hundred patients, fluoxetine can cause weight loss, blood pressure elevation, and visual disturbances. In addition, the heart rhythm may change: The so-called QT interval in the ECG may be prolonged, which is especially important to note if the patient is also taking other medications.
Psychological problems can also occur, especially at the beginning of a therapy with fluoxetine. These include, for example, anxiety, inner restlessness, thought disorders such as a slowing down of thought processes or constant brooding, sleep problems and mood swings. But suicidal thoughts or even suicide attempts have also been reported. That’s why doctors monitor patients closely during the first few weeks of treatment.
If rashes, shortness of breath or general symptoms of an allergic reaction occur, the therapy should be discontinued immediately and a doctor consulted, since, as with other allergies, life-threatening symptoms can occur.
Because of the slow rate of excretion of the active substance, it may take a particularly long time for adverse drug reactions (ADRs) to subside.
What should be considered when taking fluoxetine?
Contraindications
- known hypersensitivity to the active substance
- concomitant use of irreversible monoamine oxidase inhibitors (MAO inhibitors – used for depression and Parkinson’s disease)
- @ concomitant use of metoprolol (e.g., in hypertension, coronary artery disease)
Drug interactions
If other centrally acting drugs (i.e., drugs that act in the brain) are to be taken in addition to fluoxetine, this should be discussed with a doctor or pharmacist beforehand.
This is especially true for other antidepressants and preparations that act directly on the serotonin system, such as tryptophan, tramadol, and migraine medications (triptans such as sumatriptan, some of which are also available over the counter). In combination with fluoxetine, the so-called “serotonin syndrome” can occur, which requires immediate medical treatment!
Enzymes are involved in the degradation of fluoxetine in the liver, which also significantly degrade other active substances in the body. Therefore, simultaneous use may lead to interactions.
In addition, alcohol should be avoided during therapy with fluoxetine in order not to place additional strain on the liver (central detoxification organ).
The simultaneous use of anticoagulants can lead to increased anticoagulation and increase the risk of bleeding. Coagulation values should therefore be monitored closely, especially at the beginning of therapy.
Age restriction
The active substance fluoxetine should not be used in children under 8 years of age. In older children and adolescents under 18 years of age, a specialist starts and monitors the therapy particularly closely.
Fluoxetine can increase suicidal behavior, especially in adolescents and young adults – in some cases, suicide has actually occurred due to the drive-increasing effect of fluoxetine. This risk exists with almost all SSRIs.
Pregnancy and lactation
Various studies on pregnancy outcomes during SSRI therapy have predominantly failed to provide clear evidence of an increased rate of miscarriage. However, an increased risk of malformation under fluoxetine therapy cannot be ruled out with certainty.
The same applies to the breastfeeding period. Due to the long half-life of fluoxetine, citalopram or sertraline should also be preferred here.
How to obtain medicines containing the active ingredient fluoxetine
Fluoxetine requires a prescription in Germany, Austria and Switzerland and can only be obtained from pharmacies with a valid prescription.
Since when is fluoxetine known?
Fluoxetine was submitted for approval in the United States in 1977. After further years of investigation and evaluation of fluoxetine, it was finally approved in the US in 1987.
The patent on the active ingredient fluoxetine expired in 2001, which allowed other manufacturers to market fluoxetine in the form of generics (copycat drugs) at lower prices.
