Makindo Medical Notes

⚠️ 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.