Does Fluoxetine work straight away? (5+ factors)

In this article, we will discuss whether fluoxetine works straight away. Additionally, we will talk about how fluoxetine works, contributing factors, how to know if it is working, and what to do if fluoxetine is not working.  

Does fluoxetine work straight away?

Fluoxetine does not work straight away. Fluoxetine, also known as Prozac, may start to show improvements in depression symptoms within the first two weeks of antidepressant treatment. However, fluoxetine may show its complete therapeutic benefit after 8 weeks (1). 

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) antidepressant that is FDA-approved to treat depression (patients of age 8 years and above), eating disorders, premenstrual dysphoric disorder, obsessive-compulsive disorder (OCD), and even treatment-resistant depression in combination with Olanzapine (2).

Fluoxetine works for depression by blocking the reuptake of serotonin, a neurotransmitter in the synaptic regions of the brain. Due to this mechanism, serotonin levels are increased and they remain in the brain cells for longer periods. 

Due to the prolonged persistence of serotonin in the synaptic regions, it enhances the neurotransmission between brain cells and ultimately reduces the symptoms of depression by improving mood, appetite, emotions, sleep, and the body’s stress response (2).  

What factors influence fluoxetine’s onset of action?

The factors that may influence fluoxetine’s onset of action may include: 

Individual sensitivity: If you are sensitive to fluoxetine, you may respond to even lower doses of the medicine compared to others, and even observe improvement in depression symptoms earlier than expected. Your age, weight, or underlying health conditions may also influence fluoxetine’s onset of action. 

Individual metabolism: Every individual metabolizes the drug differently, therefore the onset of action of fluoxetine may vary among individuals. Some patients may have a slower metabolism, such as in adults compared to adult patients. 

Dosage and duration of treatment: The duration of treatment with fluoxetine and the dosage at which it is prescribed, may influence the time taken by the medicine to show its therapeutic effects. Higher doses may show comparatively quick results; however, it may also be linked with the risk of side effects. 

Concomitant use of drugs or other substances: If certain medications are used along with fluoxetine, they may delay the onset of action of the medication. Additionally, alcohol may also affect the effectiveness of fluoxetine. 

Genetic factors: The genetic variations among individuals may significantly affect the time taken by fluoxetine to start working. The genetic makeup of individuals influences how the drug is metabolized in the body, hence affecting its onset of action.  

Consistency: Fluoxetine should be taken exactly as prescribed by your healthcare provider and you should not miss a single dose. Being consistent and taking fluoxetine at the same time each day, may have a positive impact on the effectiveness of fluoxetine (3). 

How to know that fluoxetine is working?

To know that fluoxetine is working, you may have to wait for a while. If you start noticing improvements in your sleep, mood, or appetite within two weeks, it indicates that fluoxetine has started working, and your body is adjusting and responding to the antidepressant treatment. 

However, some people may not observe any improvements in the early phase of treatment with fluoxetine. Therefore, in such cases, you should wait for at least 6 weeks. If you do not notice any reduction in depression symptoms by the end of 6 weeks, there is a possibility that you may not feel better even after 8 weeks of fluoxetine treatment (1). 

What leads to fluoxetine inefficiency?

Some factors may lead to fluoxetine’s inefficiency including:

• Lower doses of fluoxetine may not be effective in achieving the desired therapeutic effect. 
• When fluoxetine is taken only for a short duration, it might not be effective, as fluoxetine may take a few weeks to show complete therapeutic effects. 
• Due to physiological variations among individuals, they may not respond to fluoxetine. 
• Being inconsistent with fluoxetine treatment may not allow it to show its therapeutic benefits. 
• Concomitant use of other medicines that may interact with fluoxetine, may also lead to inefficiency. 
• Underlying health conditions and environmental factors such as stress may also cause fluoxetine inefficiency.  

What to do if fluoxetine is not working?

If you feel that fluoxetine is not working and you do not notice any improvement in your depression symptoms after 8 weeks, please consult your healthcare provider. They may evaluate your current symptoms, family or medical history, and dosage regimen of fluoxetine.

Your doctor may adjust the dosage of fluoxetine and monitor your response after these changes. You may experience some side effects of fluoxetine after dose adjustment, such as nausea, diarrhoea, acid reflux, dry mouth, sleep disturbances, weight changes, or fatigue (4). 

However, these side effects of fluoxetine may reduce or disappear as your body adapts to the medication. If you do not respond even after dose adjustments, your doctor may recommend alternative antidepressants of the SSRI class of drugs, such as sertraline, paroxetine, citalopram, or escitalopram (5,6). 

As per my analysis, fluoxetine does not work straight away. Fluoxetine may start working within two weeks and show full efficacy after 8 weeks of consistent treatment. Several factors may influence the onset of action of fluoxetine.

However, if you notice no improvements even after 8 weeks of fluoxetine treatment, then it might not be suitable for you. Antidepressants take time to work and you should wait patiently and let the medicine work. Do not stop taking fluoxetine and always consult your doctor if you want to bring any change to your antidepressant treatment.

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