Is Prozac an SSRI?
Yes, Prozac (fluoxetine) is definitively a selective serotonin reuptake inhibitor (SSRI) that acts by specifically inhibiting the presynaptic reuptake of serotonin, thereby increasing serotonin levels in the synaptic cleft 1.
Evidence Supporting Prozac as an SSRI
According to the Mayo Clinic Proceedings, Prozac (fluoxetine) is clearly identified as a selective serotonin reuptake inhibitor that has transformed the treatment landscape for various conditions including:
- Major depressive disorder
- Obsessive-compulsive disorder (OCD)
- Panic disorder
- Posttraumatic stress disorder
- Chronic pain syndromes 1
Fluoxetine is metabolized primarily through the cytochrome P450 (CYP) 2D6 pathway and has the distinction of being the first SSRI to usher in a new era of prescription pharmacology for mental health conditions 1.
FDA-Approved Indications for Prozac
Prozac is FDA approved for:
- Major depressive disorder
- OCD
- Bulimia nervosa
- Premenstrual dysphoric disorder
- Panic disorder
- Bipolar disorder (in combination with olanzapine) 1
Notably, it is the only antidepressant FDA approved for treating major depression in children and adolescents aged 8 years or older 1.
Mechanism of Action
Fluoxetine works by:
- Selectively inhibiting serotonin uptake in the presynaptic neurons
- Having minimal effect on the reuptake of norepinephrine or other neurotransmitters
- Showing negligible binding affinity for neurotransmitter receptor sites 2
This selective action on the serotonin transporter is what classifies it as an SSRI, distinguishing it from other antidepressant classes like tricyclic antidepressants (TCAs) or serotonin-norepinephrine reuptake inhibitors (SNRIs).
Pharmacokinetics
Key pharmacokinetic properties of fluoxetine include:
- Good oral absorption
- Protein binding of approximately 94.5% 3
- Elimination half-life of 1-3 days after a single dose, increasing to 4-6 days with chronic administration
- Metabolism to an active metabolite, norfluoxetine, which also inhibits serotonin reuptake and has a longer half-life (4-16 days) 3, 2
Other SSRIs
Fluoxetine belongs to the SSRI class which also includes:
- Citalopram (Celexa)
- Escitalopram (Lexapro)
- Paroxetine (Paxil)
- Sertraline (Zoloft)
- Fluvoxamine (Luvox) 1, 4
Clinical Considerations
When prescribing Prozac, be aware of:
- Potential for drug interactions due to its inhibition of CYP2D6 5
- Black box warning for treatment-emergent suicidality, particularly in adolescents and young adults 1
- Common side effects including nausea, anxiety, insomnia, anorexia, diarrhea, nervousness, and headache 2
- Long half-life which may be advantageous when patients miss doses but requires longer washout periods when switching to MAOIs or TCAs 6
In summary, Prozac (fluoxetine) is unequivocally classified as a selective serotonin reuptake inhibitor (SSRI) based on its pharmacological mechanism of action and is recognized as one of the first and most widely used medications in this class.