Which atypical antipsychotic is approved for long-term use in preventing mood episodes in bipolar disorder?

Olanzapine is the atypical antipsychotic that is specifically approved for long-term use in preventing mood episodes in bipolar disorder. It acts on various neurotransmitter receptors in the brain, including dopamine and serotonin receptors, which helps to stabilize mood and reduce the frequency of mood episodes in individuals with bipolar disorder.

The efficacy of olanzapine in treating both manic and depressive episodes of bipolar disorder has been established through numerous clinical trials, making it a reliable choice for mood stabilization over an extended period. This aspect is especially important for patients seeking to avoid cyclical mood changes that characterize the disorder.

Other options do not fit the criteria established in the question. Risperidone, while it has some use in bipolar disorder, is not primarily indicated for long-term mood stabilization. Atomoxetine is not an antipsychotic; it is used primarily for attention-deficit hyperactivity disorder (ADHD). Fluoxetine is an antidepressant, and while it can be used in the treatment of depressive episodes in bipolar disorder, it is not used for the long-term prevention of mood episodes in the same way that olanzapine is. Thus, olanzapine stands out as the correct choice for this specific treatment approach in bipolar disorder.