Fluoxetine

What is Fluoxetine?

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) antidepressant medication used to treat various mental health conditions. It belongs to a class of drugs that work by affecting serotonin levels in the brain. Fluoxetine is primarily prescribed for depression, anxiety disorders, and obsessive-compulsive disorder.

Uses

Fluoxetine has several FDA-approved uses for treating mental health conditions:

• Major depressive disorder: The primary indication for fluoxetine, helping to improve mood, energy levels, and overall functioning in people with clinical depression.
• Obsessive-compulsive disorder (OCD): Reduces the frequency and intensity of obsessive thoughts and compulsive behaviors in both adults and children.
• Panic disorder: Helps prevent panic attacks and reduces anticipatory anxiety related to panic episodes.
• Bulimia nervosa: Used as part of comprehensive treatment to reduce binge-eating and purging behaviors in this eating disorder.
• Premenstrual dysphoric disorder (PMDD): Helps manage severe mood symptoms that occur before menstruation in some women.

How it works

Fluoxetine works by blocking the reuptake of serotonin, a neurotransmitter that plays a crucial role in regulating mood, anxiety, and other brain functions. By preventing nerve cells from quickly reabsorbing serotonin, the medication increases the amount of this chemical available in the brain. This enhanced serotonin activity is thought to improve mood and reduce symptoms of depression and anxiety disorders over time.

Side effects

Common side effects include:

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• Nausea and stomach upset
• Headache
• Drowsiness or insomnia
• Dry mouth
• Loss of appetite
• Sexual dysfunction
• Nervousness or anxiety
• Diarrhea

Serious side effects to watch for:

• Serotonin syndrome (confusion, rapid heart rate, high fever)
• Increased suicidal thoughts, especially in young adults
• Severe allergic reactions with rash or breathing difficulties
• Abnormal bleeding or bruising
• Manic episodes in people with bipolar disorder

Warnings and precautions

• Black box warning: Fluoxetine may increase suicidal thoughts and behaviors in children, adolescents, and young adults under 25, especially during the first few months of treatment.
• Pregnancy considerations: Fluoxetine is classified as pregnancy category C, meaning risks cannot be ruled out. It should only be used during pregnancy if potential benefits justify potential risks to the fetus.
• Liver impairment: Patients with liver disease may need dose adjustments since fluoxetine is metabolized by the liver.
• Bipolar disorder screening: Patients should be evaluated for bipolar disorder before starting treatment, as antidepressants can trigger manic episodes.
• Withdrawal considerations: Due to fluoxetine’s long half-life, withdrawal symptoms are generally less severe than with other SSRIs, but discontinuation should still be gradual.

Interactions

Fluoxetine has several important drug interactions due to its effects on liver enzymes:

• Monoamine oxidase inhibitors (MAOIs): Can cause dangerous serotonin syndrome; requires at least 5 weeks between stopping fluoxetine and starting MAOIs.
• Blood thinners (warfarin): Fluoxetine may increase bleeding risk by affecting warfarin metabolism.
• Tricyclic antidepressants: Fluoxetine can increase levels of these medications, potentially causing toxicity.
• Phenytoin: Fluoxetine may increase phenytoin levels, requiring dose adjustments of the seizure medication.
• NSAIDs and aspirin: Combined use may increase risk of bleeding, especially gastrointestinal bleeding.
• Tramadol: Increases risk of serotonin syndrome when used together.
• St. John’s wort: This herbal supplement can increase serotonin activity and should be avoided.
• Tryptophan supplements: May enhance serotonergic effects and increase risk of serotonin syndrome.

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Dosage

Typical adult dosages vary depending on the condition being treated:

• Depression: Usually starts at 20 mg once daily, may be increased to 40-60 mg daily if needed.
• OCD: Often requires higher doses, typically 40-60 mg daily, with some patients needing up to 80 mg daily.
• Panic disorder: Usually begins at 10 mg daily for one week, then increased to 20 mg daily.
• Bulimia nervosa: Typically 60 mg once daily.

Dosage should always be determined by a healthcare provider based on individual patient factors, response to treatment, and potential side effects. Elderly patients or those with liver impairment may require lower doses.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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