Fluoxetine
A long-established SSRI antidepressant. It lingers in the body for weeks, so withdrawal is rare but changes happen slowly. The usual choice in young people.
Quick answer: The most common side effects of fluoxetine are poor sleep, headache, nausea or diarrhoea, and tiredness. Less appetite, anxiety and sexual problems are also common. It’s an SSRI antidepressant for depression, OCD and PMDD that lasts for weeks in the body, so withdrawal is less likely. Get help urgently for thoughts of self-harm or signs of serotonin syndrome.
At a glance
- For
- Depression, OCD, PMDD; depression in young people aged 8 and over, with talking therapy
- Works
- About half of people with depression improve a lot, compared with about a third on a dummy treatment. In PMDD, about 6 in 10 improve
- Cost
- Under the $25 PBS co-payment, about $22 a month; $7.70 concession
- Kicks in
- 2–4 weeks, full effect by 6–8 weeks; PMDD can respond within days
- Taken for
- Usually 6–12 months after feeling well; PMDD may be longer or cyclical
- Watch for
- Nausea, headache, trouble sleeping, nervousness, less appetite, sexual side effects
The long half-life is a feature: a missed dose barely registers.
Brand names
- Prozac, Lovan, Zactin, plus generic brands sold as fluoxetine
How it works
A selective serotonin reuptake inhibitor (SSRI) that increases serotonin between nerve cells. It and its breakdown product last for weeks, so effects build and fade slowly.
Used for
- Major depression (TGA-approved)
- Obsessive-compulsive disorder (TGA-approved)
- Premenstrual dysphoric disorder, severe premenstrual mood symptoms (TGA-approved)
- Depression in children and teens aged 8 and over, with talking therapy and specialist guidance
Side effects
Full side-effect list (from the product information)
How often, from the official product information. Bold = serious.
Very common more than 1 in 10
- Poor sleep
- Headache
- Diarrhoea or nausea
- Tiredness
Common 1 in 10 to 1 in 100
- Less appetite, weight loss
- Anxiety, restlessness, odd dreams
- Poor focus, dizziness, tremor
- Blurred vision, palpitations, long QT
- Flushing, sweating, rash, itch
- Vomiting, indigestion, dry mouth
- Joint pain, passing urine more
- Sexual problems, vaginal bleeding
- Jittery, chills
Uncommon 1 in 100 to 1 in 1,000
- Suicidal thoughts, high mood
- Teeth grinding, twitching, poor balance
- Large pupils, ringing ears, low BP
- Nosebleeds, gut bleeding, bruising
- Hair loss, breathlessness
Rare 1 in 1,000 to 1 in 10,000
- Low blood counts, low sodium
- Anaphylaxis, angioedema
- Mania, hallucinations, aggression
- Seizures, serotonin syndrome
- Dangerous heart rhythms, hepatitis
- Severe skin reactions
- Urine retention, prolonged erection
Frequency not known reported, rate unclear
- Heavy bleeding after birth
Get help urgently if
- Fever, sweating, shaking, muscle jerks, confusion or a racing heart (possible serotonin syndrome)
- Thoughts of suicide or self-harm: Lifeline 13 11 14, or 000
- Black or bloody stools, or vomiting blood
- Face or throat swelling, trouble breathing, or a seizure
Good to know
- Young people: growth is checked. Under 25s: suicidal thoughts can increase early on. Thoughts of self-harm: see your doctor now or call Lifeline 13 11 14.
- Serotonin syndrome is more likely with tramadol, triptans, St John’s wort or other antidepressants. Never use with an MAOI, and wait 5 weeks after stopping before starting one.
- Bleeding is more likely with anti-inflammatories, aspirin or blood thinners. Interacts with tamoxifen.
- Low sodium (confusion, unsteadiness) is more likely in older people. Pregnancy or breastfeeding: discuss with your doctor.
Support lines
If you or someone else is in danger right now, call your emergency number. To talk to someone, any time:
- Australia: Lifeline 13 11 14 (24/7, or text 0477 13 11 14), Suicide Call Back Service 1300 659 467, Beyond Blue 1300 22 4636, 13YARN 13 92 76 for Aboriginal and Torres Strait Islander people. Emergency: 000.
- Young people in Australia: Kids Helpline 1800 55 1800 (24/7, ages 5 to 25) or headspace (ages 12 to 25).
- New Zealand: call or text 1737. Emergency: 111.
- UK and Ireland: Samaritans 116 123. Emergency: 999 (or 112).
- US and Canada: call or text 988. Emergency: 911.
- Anywhere else: findahelpline.com lists free helplines in more than 100 countries.
Common questions
Is fluoxetine used for PMDD?
Yes. Fluoxetine is TGA-approved for premenstrual dysphoric disorder, as well as depression and obsessive-compulsive disorder. In PMDD it can work within days.
Does fluoxetine cause withdrawal symptoms?
Withdrawal is less likely than with other antidepressants, because fluoxetine lasts for weeks in the body and its effects fade slowly.
Does fluoxetine cause weight gain?
Less appetite and weight loss are listed as common side effects.
Information only. Not a recommendation or endorsement of any product. Whether a medicine suits you depends on your health and other medicines, so talk to your doctor or pharmacist. In an emergency, call 000 (Australia) or your local emergency number. From a mobile, 112 works in most countries.
More information
- Fluoxetine SmPC (UK, Brown & Burk)
- Healthdirect: Medicines information
- Lifeline: 13 11 14
- Cipriani et al. 2018: Comparing 21 antidepressants (The Lancet)
- PBS: Fluoxetine 20 mg
maladywise.com/medicines/fluoxetine/