Prozac (Fluoxetine) Uses
Prozac (fluoxetine) is FDA approved for the treatment of major depressive disorder, obsessive-compulsive disorder (OCD), bulimia nervosa, premenstrual dysphoric disorder, panic disorder, and bipolar disorder (in combination with olanzapine). It is also the only antidepressant FDA approved for treating major depression in children and adolescents aged 8 years or older. 1, 2
FDA-Approved Indications
Major Depressive Disorder (MDD): Prozac is indicated for adults and children/adolescents (≥8 years) with symptoms including depressed mood, loss of interest, changes in weight/appetite, sleep disturbances, psychomotor changes, fatigue, feelings of worthlessness, concentration difficulties, and suicidal thoughts 2
Obsessive-Compulsive Disorder (OCD): For both adults and pediatric patients with recurrent, intrusive thoughts (obsessions) and repetitive behaviors (compulsions) that cause distress or interfere with functioning 1, 2
Bulimia Nervosa: For adults with moderate to severe bulimia, characterized by binge-eating and vomiting behaviors (at least 3 bulimic episodes per week for 6 months) 2
Panic Disorder: With or without agoraphobia, characterized by recurrent unexpected panic attacks and associated concerns about additional attacks 2
Premenstrual Dysphoric Disorder: For the treatment of premenstrual mood symptoms 1, 2
Bipolar Disorder: In combination with olanzapine for bipolar depression 1, 2
Pharmacological Mechanism
Prozac belongs to the selective serotonin reuptake inhibitor (SSRI) class of antidepressants. It works by:
- Specifically and potently inhibiting the presynaptic reuptake of serotonin 3, 4
- Having minimal effect on the reuptake of norepinephrine or other neurotransmitters 3
- Having negligible binding affinity for neurotransmitter receptor sites 3
- Being metabolized to an active metabolite (norfluoxetine) that also inhibits serotonin reuptake 3, 5
Dosing Considerations
- For major depression, the optimal dosage range appears to be 20-40 mg once daily 3
- Higher dosing strategies (60-80 mg) have shown superior efficacy for OCD 1
- For bulimia nervosa, 60 mg/day has been shown effective in maintaining response 2
- Long elimination half-life (1-3 days for single dose; 4 days for long-term administration) allows for once-daily dosing 3
Special Populations
- Pediatric Use: Fluoxetine is the only antidepressant FDA approved for major depression in children/adolescents aged 8 years or older 1, 2
- Geriatric Use: Equally effective in elderly patients compared to younger adults 1, 5
- Comorbid Anxiety Disorders: Effective in treating both depressive and anxiety symptoms in patients with comorbid anxiety disorders 6
Safety Considerations
- Black Box Warning: For treatment-emergent suicidality, particularly in adolescents and young adults 1
- Common Side Effects: Nausea, anxiety, insomnia, anorexia, diarrhea, nervousness, and headache 3, 7
- Advantages over Tricyclic Antidepressants: Fewer anticholinergic, hypotensive, and sedative effects; no particular cardiovascular effects; overdoses generally do not cause serious toxic effects 7, 5
- Drug Interactions: Clinically important interactions may occur with monoamine oxidase inhibitors, tricyclic antidepressants, and other medications 7
- Pharmacogenetic Considerations: Metabolized through cytochrome P450 (CYP) 2D6, which is subject to genetic variation and inhibition 1
Clinical Pearls
- If there is little improvement after 4-6 weeks of treatment, an alternative treatment should be considered 7
- Patients with comorbid obsessive-compulsive disorder may be less likely to respond to fluoxetine for depression compared to patients without comorbid OCD 6
- Fluoxetine may be less effective than tricyclic antidepressants for treating inpatients with severe melancholic depression 7
- Most appropriate for patients with moderate depression who can be treated as outpatients 7