Fluoxetine

Fluoxetine is an SSRI antidepressant prescribed in the UK mainly for depression. It is also used for some people with OCD, bulimia nervosa (under specialist care), or other conditions when a clinician judges it appropriate. It is not a single-dose sedative for everyday stress.

Care usually includes follow-up with your GP or mental health team and may combine with talking therapies. If you take medicines for physical health (for example Ramipril, Metformin, or Atorvastatin), your prescriber may review the whole list when starting an SSRI.

Compared with Sertraline and some other SSRIs, fluoxetine stays in the body longer (long half-life), which can affect dose changes, missed doses, and interactions — your prescriber can explain what that means for you.

Only your clinician can decide if fluoxetine is suitable, at what dose, and for how long.

SSRIs increase serotonin activity between nerve cells. Serotonin is involved in mood, sleep, and appetite. The exact way this improves depression or OCD is not fully understood, but many people gain symptom relief when medicine and support are combined.

How long does fluoxetine take to work? Sleep or anxiety may shift a little in 1–2 weeks, but mood often improves gradually over 4–6 weeks or more. Your prescriber may avoid frequent dose changes in the first weeks so your body can adjust.

If you feel more agitated, panicky, or have thoughts of self-harm after starting or increasing fluoxetine, seek urgent help — see below.

Fluoxetine dosage is individual — many adults start at 20 mg once daily; higher doses may be used under specialist supervision. Use capsules, tablets, or liquid exactly as prescribed; measure liquids carefully.

• Usually taken once daily, often in the morning because it can feel mildly stimulating; your prescriber may suggest evening dosing if sleep is unaffected or if it suits you better.

• Swallow capsules/tablets whole with water unless your leaflet says otherwise.

• What if I miss a dose? Take it when you remember unless the next dose is soon — do not take two doses together. The long half-life means occasional missed doses may be less dramatic than with some antidepressants, but consistent use still matters.

Do not stop suddenly — your GP or psychiatrist may advise a gradual reduction. Withdrawal-type symptoms can still occur if fluoxetine is stopped too quickly.

Fluoxetine side effects are often strongest in the first 1–2 weeks. Your GP or pharmacist may suggest persisting briefly, changing dose time, or reviewing treatment if symptoms are severe or do not settle.

• Nausea, diarrhoea, or reduced appetite.

• Headache, dry mouth, or increased sweating.

• Anxiety, restlessness, agitation, or insomnia — report if intense, especially in the first days of treatment.

• Yawning, tiredness, or dizziness.

• Sexual side effects: reduced desire, delayed orgasm, or erectile problems — discuss with your GP if troublesome.

• Weight change (up or down) can occur; mention large or rapid changes.

• Bruising or nosebleeds more easily — SSRIs can affect platelets; seek advice if marked, especially if you use Ibuprofen or Aspirin.

Speak to your clinician if side effects worry you — do not stop abruptly without advice.

If you feel you might act on thoughts of harming yourself, contact your crisis team, call 999, or go to A&E immediately.

• Urgent same-day help: severe agitation, confusion, shivering, high fever, muscle stiffness, diarrhoea, or fast heartbeat — possible serotonin syndrome, especially if combined with Tramadol, triptans, St John’s wort, or other antidepressants.

• Urgent help: sudden manic or hypomanic symptoms (very high energy, reduced sleep, reckless spending or behaviour), fits, severe allergic reaction, or vomiting blood (uncommon — may relate to bleeding risk with NSAIDs).

• Low sodium in the blood (hyponatraemia) can cause confusion, unsteadiness, or fits — more concern in older adults or with diuretics; seek prompt medical advice for new confusion or severe headache.

• Glaucoma: seek urgent eye care for severe eye pain or sudden vision loss if you are at risk.

Young adults and teenagers may need closer monitoring in the first weeks — keep booked reviews with your GP or mental health team.

What if I miss a dose? Take it when you remember unless your next dose is due within a few hours — then skip the missed dose. Do not take a double dose.

Because fluoxetine lingers in the body, occasional missed doses may cause less immediate fluctuation than with some shorter antidepressants, but regular dosing still supports steady mood. A phone alarm or dosette box can help.

Do not take fluoxetine if you are allergic to it or any ingredient, or if you are taking or have recently stopped an MAOI — dangerous interactions can occur. Your prescriber must define a safe washout period between MAOIs and fluoxetine.

• Caution if you have epilepsy (SSRIs may lower seizure threshold), bipolar disorder (risk of mania), significant bleeding risk, angle-closure glaucoma risk, or severe liver problems.

• Children and adolescents: usually specialist mental health prescribing only.

Never combine fluoxetine with St John’s wort, tryptophan supplements, or other serotonergic products without medical advice.

Can I take fluoxetine with other medicines? It interacts with many drugs — other antidepressants, Tramadol, triptans, some antipsychotics, anticoagulants and antiplatelets (bleeding risk), and NSAIDs such as Ibuprofen (stomach bleed risk). Always ask a pharmacist before adding anything, including cold and cough products.

Combining fluoxetine with Ibuprofen or Aspirin increases bleeding risk for some people — your GP or pharmacist may suggest Paracetamol for some types of pain instead.

Alcohol can worsen sedation and low mood and may impair judgement. Your GP or pharmacist may advise limiting alcohol, especially when starting or changing dose.

Driving: fluoxetine can cause dizziness or slowed reaction at first — your prescriber may advise caution until you know how you respond.

Decisions in pregnancy balance risks of untreated depression with medicine safety. Speak to your GP or psychiatrist before changing fluoxetine — do not stop suddenly without a plan.

Small amounts pass into breast milk; many mothers continue SSRIs when needed. Your prescriber can discuss lowest effective dose and baby monitoring.

Expect reviews around 1–2 weeks and again at 4–6 weeks after starting or changing dose to discuss mood, sleep, side effects, and safety. Under-25s may be seen more often in early treatment.

Routine blood tests are not usually required only for fluoxetine, but weight, blood pressure, or glucose may be checked if you have diabetes or take other medicines.

Alternatives depend on your diagnosis, past response, side effects, and other health issues. Your GP or psychiatrist may consider other SSRIs (for example Sertraline or Citalopram), SNRIs, tricyclics such as Amitriptyline for certain pain/mood patterns, or psychological therapy alone or with tablets — these are classes and options, not recommendations for you personally.

Because fluoxetine lasts a long time in the body, switching antidepressants often needs a careful cross-taper planned by your prescriber.

• Lifestyle support (sleep routine, activity, alcohol limits, social contact) complements any change in prescription.

Do not switch or stop without medical guidance.