Fluoxetine: Difference between revisions
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| structure = Fluoxwhite.svg | | structure = Fluoxwhite.svg | ||
| classes = SSRI, Anxiolytic, Antidepressant | | classes = SSRI, Anxiolytic, Antidepressant | ||
| uses = Anxiety, premature ejaculation, low mood | | uses = <vote slug="anxiety-use">Anxiety</vote>, <vote slug="premature-ejaculation-use">Premature ejaculation</vote>, <vote slug="low-mood-use">Low mood</vote> | ||
| starting_dose = 10 mg | | starting_dose = 10 mg | ||
| preparations = 10 mg, 20 mg, 40 mg caps | | preparations = 10 mg, 20 mg, 40 mg caps | ||
| Line 13: | Line 13: | ||
| 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<ref name ="lactmed">https://www.ncbi.nlm.nih.gov/books/NBK501186/</ref> | | pregnancy = Category C<ref name="lactmed">https://www.ncbi.nlm.nih.gov/books/NBK501186/</ref> | ||
| legal = Rx-only in US | | legal = Rx-only in US | ||
| mechanism = TrkB/BDNF<ref name="trkb">https://pmc.ncbi.nlm.nih.gov/articles/PMC9666396/</ref> <vote slug="ssri-claim">Fluoxetine is a selective serotonin reuptake inhibitor.</vote> | | mechanism = TrkB/BDNF<ref name="trkb">https://pmc.ncbi.nlm.nih.gov/articles/PMC9666396/</ref> <vote slug="ssri-claim">Fluoxetine is a selective serotonin reuptake inhibitor.</vote> | ||
| intro = 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. | | intro = 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. | ||
| | | indications = <indication slug="depression" title="Depressive disorders" author="MDElliottMD"/> | ||
<indication slug="anxiety-disorders" title="Anxiety disorders broadly" author="MDElliottMD"> | |||
Including generalized anxiety, panic, and social anxiety. | |||
</indication> | |||
<indication slug="panic" title="Panic disorder" author="MDElliottMD"/> | |||
<indication slug="social-anxiety" title="Social anxiety disorder" author="MDElliottMD"/> | |||
<indication slug="ocd" title="Obsessive-compulsive disorder" author="MDElliottMD"/> | |||
<indication slug="ptsd" title="PTSD" author="MDElliottMD"> | |||
Potentially. | |||
</indication> | |||
| dosing = <titration slug="standard" author="MDElliottMD" title="Standard adult or child"> | | dosing = <titration slug="standard" author="MDElliottMD" title="Standard adult or child"> | ||
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. | 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. | ||
| Line 30: | Line 34: | ||
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). | 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). | ||
</titration> | </titration> | ||
| effects = <effect ref="anxiolysis" author="MDElliottMD">Classically starting at 3–4 weeks and improving for another 8–12.</effect> | | effects = | ||
<effect ref="delayed-ejaculation" author="MDElliottMD"/> | * <effect ref="anxiolysis" author="MDElliottMD">Classically starting at 3–4 weeks and improving for another 8–12.</effect> | ||
<effect ref="mood-enhancement" author="MDElliottMD"/> | * <effect ref="delayed-ejaculation" author="MDElliottMD"/> | ||
<effect ref="nausea" author="MDElliottMD">Common, often improves over 1–2 weeks.</effect> | * <effect ref="mood-enhancement" author="MDElliottMD"/> | ||
<effect ref="decreased-libido" author="MDElliottMD"/> | * <effect ref="nausea" author="MDElliottMD">Common, often improves over 1–2 weeks.</effect> | ||
<effect ref="temporary-erectile-dysfunction" author="MDElliottMD"/> | * <effect ref="decreased-libido" author="MDElliottMD"/> | ||
<effect ref="persistent-sexual-dysfunction" author="MDElliottMD"> | * <effect ref="temporary-erectile-dysfunction" author="MDElliottMD"/> | ||
* <effect ref="persistent-sexual-dysfunction" author="MDElliottMD">Historically [https://pmc.ncbi.nlm.nih.gov/articles/PMC11450419/ associated with SSRIs].</effect> | |||
</effect | | pk_absorption = 70–90%<ref name="statpearls">https://www.ncbi.nlm.nih.gov/books/NBK459223/</ref> oral bioavailability. | ||
| pk_distribution = 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).<ref name="statpearls"/> | |||
| pk_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. | |||
| pk_elimination = | |||
| pharmacodynamics = | |||
| contraindications = MAO-Is, history of severe mania (without a mood stabilizer) | | contraindications = MAO-Is, history of severe mania (without a mood stabilizer) | ||
| interactions = | | interactions = | ||
Revision as of 04:48, 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
<indication slug="depression" title="Depressive disorders" author="MDElliottMD"/> <indication slug="anxiety-disorders" title="Anxiety disorders broadly" author="MDElliottMD"> Including generalized anxiety, panic, and social anxiety. </indication> <indication slug="panic" title="Panic disorder" author="MDElliottMD"/> <indication slug="social-anxiety" title="Social anxiety disorder" author="MDElliottMD"/> <indication slug="ocd" title="Obsessive-compulsive disorder" author="MDElliottMD"/> <indication slug="ptsd" title="PTSD" author="MDElliottMD"> Potentially. </indication>
+ 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.Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Delayed orgasm/ejaculation 0% — (n=3) ~80% +33.0 (n=1)Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Mood enhancement no reports yet ~5% +67.0 (n=1)Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Nausea no reports yet ~5% -33.0 (n=1)Common, often improves over 1–2 weeks.Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Decreased libido no reports yet ~33% -100.0 (n=1)Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Temporary erectile dysfunction no reports yet ~20% -67.0 (n=1)Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
- Persistent Sexual Dysfunction no reports yet ~0% -100.0 (n=1)Historically associated with SSRIs.Did you experience this?How often have you seen this?How was it? (-100 worst, +100 best)How was it? (-100 worst, +100 best)
Pharmacokinetics
Absorption
70–90%[3] oral bioavailability.Distribution
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).[3]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
US FDA Max
40 mg/d