Sertraline vs Fluoxetine
UK-focused comparison — general information, not personalised medical advice.
Overview
Sertraline and fluoxetine are both selective serotonin reuptake inhibitor (SSRI) antidepressants commonly prescribed in the UK for depression and several anxiety disorders when a doctor or mental health clinician judges them appropriate. They increase serotonin activity in the brain, but they are not identical medicines.
Response and side effects vary from person to person. This comparison explains typical similarities and differences in plain language; it does not tell you which one you should take or how to stop or swap treatment — those decisions need professional oversight.
What is each medicine used for?
Sertraline
Sertraline is used for major depression and for conditions such as obsessive–compulsive disorder (OCD), panic disorder, post-traumatic stress disorder (PTSD), and social anxiety disorder when a prescriber selects it as part of a care plan.
Treatment may combine with talking therapies and follow-up appointments to monitor mood and side effects.
Fluoxetine
Fluoxetine is also used for depression and for several anxiety-related conditions including OCD and bulimia nervosa in some treatment pathways, as decided by a specialist or GP according to licensed indications and your situation.
Like sertraline, it is usually part of broader support, not a stand-alone answer for everyone.
Key differences between Sertraline and Fluoxetine
- Licensed indications overlap but are not identical — your prescriber matches the medicine to your diagnosis and guidelines.
- Fluoxetine’s long half-life means it clears more slowly; this can be an advantage or a disadvantage when adjusting treatment.
- Interaction and side-effect profiles are similar as a class (SSRIs) but not the same in every detail — for example, bleeding risk with NSAIDs, effects on sleep, or sexual side effects may differ individually.
- Dosing schedules and available formulations (liquid, capsules) may influence choice if swallowing or precise doses are an issue.
Side effects: how do they compare?
- Common SSRI effects include nausea, headache, sleep change, anxiety or agitation in the first days, sweating, and sexual dysfunction. Many people find these improve after the first few weeks.
- Both carry a small increased risk of bleeding with NSAIDs or anticoagulants; your prescriber may advise on combinations.
- Young adults and teenagers may need closer monitoring when starting antidepressants for mood changes or suicidal thoughts — UK practice includes safety netting and follow-up.
- Stopping suddenly can cause withdrawal-like symptoms; dose changes should be guided by your prescriber.
Safety and who may need extra GP or pharmacist advice
- Do not combine with MAOIs or within unsafe switching windows — antidepressant changes must be medically supervised.
- Avoid St John’s wort with SSRIs.
- Seek urgent help for thoughts of self-harm, severe agitation, or symptoms suggestive of serotonin syndrome (high fever, confusion, muscle stiffness, shivering).
- Discuss pregnancy or breastfeeding plans before changing antidepressants.
How your prescriber may choose between them
- Your GP or psychiatrist considers previous antidepressant response, anxiety versus depression prominence, other mental health diagnoses, and physical health.
- They review drug interactions (for example tramadol, triptans, linezolid, other antidepressants).
- If one SSRI causes unacceptable side effects, another SSRI or a different class may be tried — this is a stepped, supervised process.
When to speak to your GP or pharmacist
- If mood worsens or you have new suicidal thoughts after starting or changing dose.
- If side effects are severe or do not improve.
- Before taking over-the-counter painkillers, migraine treatments, or herbal products alongside your SSRI.
- If you wish to reduce or stop treatment — tapering is usually safer than abrupt stopping.
Read the full medicine guides
Each DrugABC medicine page covers uses, how to take it, interactions, pregnancy, and more — for reference alongside what your clinician tells you.
Other comparisons
Reviewed by UK registered pharmacists
Reviewed by UK registered pharmacists for accuracy and clarity. Content is informational only.
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Need personalised advice?
Your local pharmacist or GP surgery can help with questions about your medicines, side effects, and alternatives that may be suitable for you.
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