Fluoxetine

What it is

Fluoxetine is a selective serotonin reuptake inhibitor. It blocks the reabsorption of serotonin back into nerve endings, which raises the amount of serotonin available at the synapse and, over time, shifts mood and anxiety regulation. Where it is marketed, it is used in depression and in anxiety disorders; in Japan the PMDA has never approved it and it is not sold.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Depression
• Anxiety

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

It can be taken with or without food and is usually placed in the morning, because it tends to be activating and can disturb sleep; appetite may rise or fall in the early weeks. The full effect is not immediate and builds over weeks, so an early absence of change is not a sign of failure. Combining it with another serotonergic antidepressant such as sertraline, or with a triptan like sumatriptan, adds serotonin on top of serotonin; combining it with ibuprofen or other anti-inflammatories raises the risk of stomach and other bleeding. Blood sodium can drop, which is why it is worth checking.

When to see a doctor

Confusion, marked drowsiness, headache or unsteadiness may point to low sodium, and agitation with fever, sweating, tremor or a racing heart after adding another serotonergic drug needs same-day assessment. Black stool, vomited blood or unexplained bruising while also using anti-inflammatories, and any wish to stop the drug, are reasons to see a doctor rather than adjust things alone.

Worth knowing

• Do not stop abruptly
• Takes weeks to work
• Can disturb sleep
• Can change appetite

Markers to watch

• Sodium