Fluoxetine

Uses

Fluoxetine is licensed for a broad range of psychiatric and non-psychiatric conditions:

• Major depressive disorder (MDD): First-line pharmacological treatment for mild to severe depression, often combined with talking therapies. Effective in reducing core symptoms such as low mood, hopelessness, fatigue, and poor concentration.
• Anxiety disorders: Approved for panic disorder, social anxiety, and obsessive-compulsive disorder (OCD). In OCD, fluoxetine helps reduce intrusive thoughts and compulsive behaviours when taken consistently over months.
• Bulimia nervosa: Uniquely licensed among SSRIs for this eating disorder. Shown to decrease binge–purge cycles and associated emotional distress.
• Premenstrual dysphoric disorder (PMDD): Sometimes prescribed in intermittent or continuous dosing schedules.
• Youth depression and OCD: In many countries, fluoxetine is the only SSRI approved for use in children/adolescents, though careful monitoring is mandatory.
• Off-label: Post-traumatic stress disorder (PTSD), fibromyalgia, hot flushes in menopause, and neuropathic pain—evidence is variable.

Dosing

Typical adult starting dose is 20 mg daily, taken in the morning. Dose may be increased in 10–20 mg increments up to 60 mg/day (sometimes 80 mg in OCD). Because of its long half-life, fluoxetine can be dosed every other day in sensitive patients or at the end of therapy tapering. For adolescents, lower starting doses (10 mg) are often used. Dose adjustments take several weeks to show full effect, so clinicians avoid rapid changes. Adherence and regular review are critical.

Side Effects

Most side effects are mild to moderate and improve over time, but some persist. Monitoring is essential, especially early in treatment.

Common

• Gastrointestinal upset: nausea, diarrhoea, indigestion, loss of appetite.
• Sleep disturbance: insomnia, vivid dreams, or early morning waking.
• Headache, dizziness, tremor, sweating.
• Sexual dysfunction: reduced libido, difficulty achieving orgasm, erectile dysfunction in men.
• Anxiety or agitation when starting, sometimes requiring slower titration.

Less common

• Weight changes: some patients lose weight initially; long-term changes vary.
• Dry mouth, blurred vision, skin rashes.
• Bruising or nosebleeds (platelet effects).

Serious

• Suicidality: especially in young people at the beginning of treatment—requires close monitoring.
• Serotonin syndrome: rare but potentially fatal, with agitation, confusion, fever, rapid heart rate, sweating, muscle stiffness, tremor, diarrhoea, and seizures.
• Hyponatraemia: low sodium, particularly in elderly or those on diuretics; may cause confusion, seizures, or unsteadiness.
• Seizures: can lower threshold in predisposed patients.

Patients should be educated to report new or worsening mood symptoms, self-harm thoughts, or sudden changes in behaviour. Emergency medical help is required for serotonin syndrome symptoms.

Warnings & Precautions

• Suicide risk: Young adults, adolescents, and children are at increased risk of suicidal thoughts, especially in the first weeks. Prescribers must monitor closely and involve family/carers in observation.
• Bipolar disorder: Fluoxetine can trigger mania/hypomania in undiagnosed bipolar patients; screening for history of manic episodes is essential before starting therapy.
• Seizure disorders: Use with caution; dose adjustments or alternative agents may be necessary.
• Liver disease: Metabolised by CYP2D6; dose reduction may be required in hepatic impairment.
• Pregnancy and breastfeeding: Use only if benefits outweigh risks. Linked to neonatal adaptation syndrome and, rarely, persistent pulmonary hypertension of the newborn (PPHN). Small amounts transfer into breastmilk.
• Drug withdrawal: Because of long half-life, discontinuation effects are usually mild but can still occur with abrupt cessation.

Patients should be encouraged to engage in concurrent non-drug therapies (CBT, exercise, sleep hygiene) for optimal recovery. Regular follow-up appointments are vital to monitor progress and adjust therapy.