Intro
Brand Name: Prozac
Class: SSRI
MOA: Selective Serotonin Reuptake Inhibitor
Secondary pharmacologic property: 5HT2C antagonism = increased NE and DA
Indications:
FDA indications: MDD (8y/o and older), OCD (7y/o and older), PMDD, Bulimia Nervosa, Panic Disorder, Bipolar Depression & Treatment-resistant Depression (when combined with Olanzapine [Symbyax])
Off-label uses: Premature ejaculation
Dosing
Forms: Caspule: 10, 20, 40 Tablet: 10, 15, 20, 60
Liquid: 20mg/5mL-120mL bottles
Weekly capsule: 90mg
Olanzapine-Fluoxetine (Symbyax): 3/25, 6/25, 12/25, 12/50
Starting: 20mg qDay
Maintenance: 20-80mg
Max: 80mg
Pharmacokinetics
Half-life:
-Fluoxetine (parent drug): Acute use 1-3 days, Chronic use 4-6 days
-Norfluoxetine (active metabolite): 1-2 weeks
Substrate of: CYP2D6
Inhibits: CYP2D6, CYP3A4
Side Effects
Many side effects go away with time
Serious: Serotonin Syndrome, SIADH, increased risk of SI in children
Notable: Sexual dysfunction (delayed ejaculation, ED, anorgasmia), GI (n/v/d, dec appetite), Sedation, Bruising
Augmentation agents for side effects:
-Consider another SSRI or antidepressant prior
-Insomnia: trazodone
-Sexual dysfunction: bupropion, sildenafil
-Emotional flattening/cognitive slowly: bupropion
Gems
-For patients receiving 40mg or less p/ day, taper generally not needed due to long half-life
-Long half life also means that occasional missed doses are of less consequence relative to other SSRIs
-Wait 5 weeks before after stopping fluoxetine before initiating an MAOI (compared to 2 weeks after stopping other SSRIs before starting MAOI)
-If switching from fluoxetine to another SSRI, can consider a washout period but generally do not need to wait for fluoxetine to be entirely cleared
-Has activating properties which make it ideal for patients with atypical depression (hyperphagia, hypersomnia)
=>Activating effects are thought to be due to 5HT2C antagonism, which increases DA and NE = activating profile
-Consider avoiding in anxious patients or those with insomnia due to activation properties
-There is a weekly capsule of Fluoxetine available
-Approved for acute and maintenance tx of bulimia nervosa, however avoid in Anorexia (risk of decreased appetite and weight loss)
-Fluoxetine-Olanzapine can be used to tx Bipolar Depression & Treatment-resistant unipolar depression
Special Populations
Renal Impairment: No dose adjustment
Hepatic Impairment: Fluoxetine is by liver. Give lower doses or less frequently due to long 1/2 life.
Elderly (60y/o+): At greater risk for hyponatremia. Start with 10-20mg. Can increase slowly with caution if needed.
Adolescents: Indicated for MDD (8+) & OCD (7+).
Breast feeding: Some drug may be found in mother’s breast milk
References
Prescriber’s Guide: Stahl’s Essential Psychopharmacology