Description: Fluoxetine is a Selective Serotonin Reuptake Inhibitor (SSRI). SSRIs work by blocking the reabsorption of serotonin back into the nerve cells where it was released. This increases the amount of serotonin floating around in the synapses between neurons and makes it easier for them to connect with each other. As a result, people who take fluoxetine feel less depressed and anxious.