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Resources › Psychotropics A-Z › Fluoxetine | Prozac | Prozac
Selective Serotonin Reuptake Inhibitor (SSRI)

Fluoxetine | Prozac

Clinical Overview

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) indicated for depression, obsessive-compulsive disorder, bulimia nervosa, and panic disorder. It was the first SSRI approved and remains one of the most widely prescribed antidepressants due to its efficacy and relatively favorable side effect profile.

Primary Clinical Applications

Fluoxetine is effective for major depressive disorder, OCD, bulimia nervosa, and panic disorder. Its long half-life provides some protection against discontinuation syndrome and allows for weekly dosing formulations. It is often considered first-line treatment for depression and anxiety disorders.

Mechanism and Pharmacological Advantages

Fluoxetine selectively inhibits serotonin reuptake with minimal effects on other neurotransmitters. Its long half-life (4-6 days) and active metabolite norfluoxetine (4-16 days) provide sustained therapeutic effects and reduce withdrawal symptoms when discontinued.

Clinical Considerations

The extended half-life means steady-state levels are achieved slowly (4-5 weeks) but also provides built-in tapering when discontinued. Fluoxetine may be activating in some patients and is often given in the morning. The weekly formulation improves adherence for maintenance therapy.

Prescribing Information

Dosing & Administration

Major Depressive Disorder – Adults:

  • Initial: 20 mg once daily in the morning
  • Range: 20-80 mg daily
  • Maximum: 80 mg daily
  • Weekly formulation: 90 mg once weekly (after stabilization on daily dosing)

OCD – Adults:

  • Initial: 20 mg daily in the morning
  • Range: 20-60 mg daily
  • Maximum: 80 mg daily

Bulimia Nervosa:

  • Recommended dose: 60 mg once daily in the morning

Panic Disorder:

  • Initial: 10 mg daily for 1 week, then 20 mg daily
  • Range: 10-60 mg daily

Pediatric Depression (8-18 years):

  • Initial: 10-20 mg daily
  • Range: 10-60 mg daily

Indications

  • Major depressive disorder (adults and pediatric patients ≥8 years)
  • Obsessive-compulsive disorder (adults and pediatric patients ≥7 years)
  • Bulimia nervosa (adults)
  • Panic disorder with or without agoraphobia (adults)

Contraindications

  • Hypersensitivity to fluoxetine
  • Use with MAOIs (within 14 days of discontinuation)
  • Use with pimozide or thioridazine
  • Use with linezolid or IV methylene blue

Warnings & Precautions

  • Boxed Warning: Increased risk of suicidal thoughts and behavior in patients under 25 years
  • Serotonin syndrome: Risk with concurrent serotonergic drugs
  • Activation of mania: Monitor in patients with bipolar disorder
  • Abnormal bleeding: Increased risk with anticoagulants
  • Hyponatremia: Particularly in elderly patients
  • Sexual dysfunction: Common side effect

Drug Interactions

  • MAOIs: Contraindicated – minimum 5 weeks washout when switching from fluoxetine
  • CYP2D6 substrates: Fluoxetine inhibits CYP2D6
  • Warfarin: Increased bleeding risk
  • NSAIDs: Increased bleeding risk
  • Highly protein-bound drugs: Potential displacement interactions

Adverse Reactions

Common (≥5%):

  • Nausea, diarrhea, dry mouth, somnolence, dizziness
  • Insomnia, nervousness, anxiety, tremor
  • Sexual dysfunction, decreased appetite

Serious:

  • Serotonin syndrome, abnormal bleeding, hyponatremia

Special Populations

  • Hepatic Impairment: Reduce dose or increase dosing interval
  • Renal Impairment: No dose adjustment typically needed
  • Elderly: Start with lower doses, monitor for hyponatremia
  • Pregnancy: Category C – use only if benefits outweigh risks
  • Pediatric: Monitor growth and development
Medical Disclaimer: This information is for educational purposes only and is not intended as medical advice. Always consult with qualified healthcare professionals before making any treatment decisions. Individual patient circumstances may vary significantly.