Fluoxetine: Difference between revisions
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| halflife = 1–4 days (7–15 days for norfluoxetine) | | halflife = 1–4 days (7–15 days for norfluoxetine) | ||
| bioavailability = 70–90% (oral) | | bioavailability = 70–90% (oral) | ||
| pregnancy = Category C | | pregnancy = Category C<ref>https://www.ncbi.nlm.nih.gov/books/NBK501186/</ref> | ||
<ref>https://www.ncbi.nlm.nih.gov/books/NBK501186/</ref> | |||
| legal = Rx-only | | legal = Rx-only | ||
| mechanism = [https://pmc.ncbi.nlm.nih.gov/articles/PMC9666396/ TrkB/BDNF] <vote slug="ssri-claim">Fluoxetine is a selective serotonin reuptake inhibitor.</vote> | | mechanism = [https://pmc.ncbi.nlm.nih.gov/articles/PMC9666396/ TrkB/BDNF] <vote slug="ssri-claim">Fluoxetine is a selective serotonin reuptake inhibitor.</vote> | ||
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</anecdote> | </anecdote> | ||
| seealso = [[Sertraline]], [[Duloxetine]] | | seealso = [[Sertraline]], [[Duloxetine]] | ||
| references = | | references = <references/> | ||
}} | }} | ||
Revision as of 02:17, 13 May 2026
SSRI, Anxiolytic, Antidepressant
Fluoxetine
Prozac
Fluoxetine was the first of a long line of SSRIs. It is notable for its extremely long half-life and relative lack of withdrawal syndrome. It can also be useful in helping taper and discontinue other SxRI medicines.
None required
Sertraline, Duloxetine
Experience
No personal reports yet
1 provider report · avg efficacy 40.0/100 · avg side-effect burden 40.0/100 · 150 patients managed total
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Problems
Anxiety disorders broadly (including panic, social anxiety, OCD), depressive disorders, potentially PTSD
+ Add a problemTitration strategies
Standard adult or child+1
Start no higher than 10 mg for the first dose. May increase by 10 mg every 2–12 weeks, or remain at 10 mg if the response is adequate, up to a typical starting maximum of 40 mg. Absolute max: 80 mg.
OCD+1
Start at 10 mg daily; increase by 10–20 mg every 2–6 weeks, up to 80 mg. OCD typically requires elevated doses (60–80 mg).
Effects
Anxiolysis no reports yet ~33% +67.0 (n=1)
Classically starting at 3–4 weeks and improving for another 8–12.
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Delayed orgasm/ejaculation 0% — (n=3) ~80% +33.0 (n=1)
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Mood enhancement no reports yet ~5% +67.0 (n=1)
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Nausea no reports yet ~5% -33.0 (n=1)
Common, often improves over 1–2 weeks.
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Decreased libido no reports yet ~33% -100.0 (n=1)
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Temporary erectile dysfunction no reports yet ~20% -67.0 (n=1)
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Persistent Sexual Dysfunction no reports yet ~0% -100.0 (n=1)
Persistent sexual dysfunction, historically associated with SSRIs
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Pharmacokinetics
Absorption
70-90% Oral bioavailabilityDistribution
Fluoxetine has plasma protein binding of approximately 94.5%, bound to albumin and alpha-1 glycoprotein. Fluoxetine readily crosses the blood-brain barrier, with a brain-to-plasma ratio of 2.6:1 in humans. The volume of distribution (Vd) of fluoxetine and its metabolite ranges between 20 to 42 L/kg. Some studies report that fluoxetine has the maximum volume of distribution (Vd) of any SSRI (between 14 and 100 L/kg).Metabolism
Fluoxetine's active metabolite is norfluoxetine, produced when the cytochrome P450 enzyme (CYP2D6) acts on it. Prescribers must remember that fluoxetine has several drug-drug interactions due to its metabolism through the CYP2D6 isoenzyme. Additionally, norfluoxetine can have an inhibitory effect on CYP3A4. Fluoxetine has a half-life of 2 to 4 days, and its active metabolite norfluoxetine has a half-life of 7 to 9 days. Approximately 7% of individuals definitively exhibit poor metabolism of fluoxetine due to reduced activity of CYP2D6.Monitoring
Relevant anecdote
⚕️ Provider 0
Fluoxetine is great for getting off other SxRIs! Especially venlafaxine and duloxetine.
Relevant Literature
No literature entries yet.
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See also
References
Summary
Classes
SSRI, Anxiolytic, Antidepressant
Common uses
- Premature ejaculation2.1n=2
- Anxiety disorders broadly1.5n=2
- Panic disorder1.5n=2
- Depressive disorders1.1n=1
- Embarrassment0.5n=3
Pharmacy
Starting dose
10 mg
Preparations
10 mg, 20 mg, 40 mg caps