Which of the following is classified as a mood stabilizer?

Lithium is classified as a mood stabilizer primarily used in the treatment of bipolar disorder. It functions by moderating mood swings and reducing the intensity and frequency of manic and depressive episodes. The exact mechanism of action of lithium is not completely understood, but it is believed to influence several neurotransmitter systems, including serotonin and norepinephrine, and modulates intracellular signaling pathways.

Mood stabilizers like lithium are specifically designed to stabilize mood without the extreme side effects often associated with antidepressants or antipsychotic medications. Patients on lithium require regular monitoring of kidney function and serum lithium levels to avoid toxicity, which can occur if levels become too high.

Other options, such as Risperdal and Zyprexa, are antipsychotic medications primarily used to treat schizophrenia and other psychotic disorders, as well as mood stabilization in some cases; however, they are not classified specifically as mood stabilizers. Thorazine is also an antipsychotic used mainly in the treatment of schizophrenia and acute psychotic states, and it is not recognized as a mood stabilizer. Thus, lithium stands out as the correct answer regarding mood stabilization.