Participants are admitted to the NIH Clinical Center for about 10 weeks. During the first 1 to 2 weeks, they are evaluated and tapered off any antidepressant or mood stabilizers they have been taking. They remain free of all medication for 2 weeks and are then randomly assigned to take either ceftriaxone or placebo for 6 weeks. The study drugs are given intravenously (through a vein) every day. To minimize discomfort, patients are given a PICC line - a tube that is inserted in a vein in the arm and remains there for the duration of drug treatment. This prevents the need for repeated intravenous injections.