How long do fluoxetine side effects last? Heard long half life.

Usually 1-2 weeks. The amount of time it takes for side effets to go away is how long it takes certain receptors to change and thus get used to the effect. This is somewhat independent of how long the drug takes to go away, so long as the concentration remains constant. The half life means that the drug stays in the system a long time and is important when mixing other drugs with it.