Purpose: This study will examine whether the drug ceftriaxone can help patients with bipolar depression during short-term treatment of symptoms such as depressed mood, psychomotor retardation (slowed down thinking and movements), and problems with sleep. Recent studies suggest that abnormalities in the brain levels of the chemical glutamate may be involved in causing depression. Ceftriaxone increases a protein in the brain called GLT1, which is responsible for regulating brain levels of glutamate.