⚠️ Serotonin syndrome risk if combined with MAOIs or St John’s wort. ❌ Do not give both within 2 weeks of each other. 💡 Always taper SSRIs gradually to avoid withdrawal effects.

📖 About

Always check the BNF link here for the most up-to-date prescribing guidance.

Class: Selective Serotonin Reuptake Inhibitor (SSRI).
Profile: First widely available SSRI; less cardiotoxic in overdose compared with tricyclic antidepressants (TCAs).
Pharmacokinetics: Long half-life (2–4 days; active metabolite norfluoxetine up to 16 days) → allows once-daily dosing but increases risk of drug interactions.

⚡ Action

Blocks presynaptic serotonin reuptake, increasing serotonin availability in the CNS.
Improves mood, reduces anxiety, and stabilises affect through modulation of serotonergic pathways.
Clinical effect may take 2–4 weeks; full response can take 6–8 weeks.

🎯 Indications & Dose

Depression: 20–60 mg PO once daily.
Panic Disorder: 20–60 mg PO once daily (start low, titrate slowly).
Bulimia Nervosa: Sometimes used (off-label in some regions), 60 mg daily.
Obsessive–Compulsive Disorder (OCD): Effective at higher doses.

💡 Elderly and hepatic impairment: start at the lowest possible dose due to slower clearance.

🔄 Interactions

Serotonin Syndrome: Avoid with MAOIs, St John’s Wort, triptans, and linezolid.
CYP2D6 Inhibition: Can increase levels of TCAs, benzodiazepines, haloperidol, risperidone, lithium, and clozapine.
❗ May increase citalopram levels → ↑ risk of QT prolongation.
Always check interactions in BNF before prescribing in polypharmacy.

⚠️ Cautions

Discontinuation syndrome if stopped abruptly (esp. dizziness, sensory symptoms, mood swings).
Do not start within 2 weeks of stopping an MAOI (or 5 weeks after fluoxetine before starting an MAOI due to its long half-life).
Use with caution in: epilepsy, bipolar disorder (may precipitate mania), glaucoma, cardiac disease, or those receiving ECT.

🚫 Contraindications

Active manic episode.
Congenital or acquired long QT syndrome (fluoxetine can prolong QT interval).

💥 Side Effects

Common: Nausea, diarrhoea, headaches, anxiety, insomnia, agitation.
Neurological: Seizures (rare), tremor, extrapyramidal symptoms.
Metabolic: Hyponatraemia (SIADH), especially in the elderly.
Sexual dysfunction: Impotence, reduced libido, anorgasmia.
Serious: Serotonin syndrome, suicidal ideation (especially in <25 years).

📌 Clinical Pearls

Because of its long half-life, fluoxetine is less likely to cause withdrawal symptoms compared to other SSRIs.
Often a good first-line SSRI for younger patients with depression/anxiety.
Less suitable in the elderly or in polypharmacy due to interaction risk.
Always review patients within 1–2 weeks of starting (or sooner if <25 years) to assess for suicidal thoughts.

📚 References

BNF – Fluoxetine
NICE Depression and Anxiety Guidelines.

The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms.

Fluoxetine