Fluoxetine
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. It is used in depression and in anxiety disorders.
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.
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.
Reference information, not medical advice. Discuss any change with your doctor.