Patients will be screened over the telephone. Information will be gathered from the mental health treatment team and the patient. Most patients who come to this study have had an inadequate or insufficient improvement with clozapine. Upon arrival at the NYS Psychiatric Institute, they review and sign consent to make sure the details of the research study are understood. Comprehensive assessments are conducted, including neurocognitive testing, prior to treatment onset. The treatment is randomized so patients will either receive IV ceftriaxone or IV placebo. Treatment is given Monday through Friday to enable the patient to have weekends off without a plastic tube (angiocath) in the vein of the arm. If after 6 weeks the patient's symptoms are not at least mildly improved, then the treatment will be stopped. If however there are signs of improvement, the treatment will be continued another 2 weeks. If at the end of the "double-blind" part of the study a patient learns he/she received placebo and wishes to be given ceftriaxone, we will provide 4 weeks of ceftriaxone for those patients. The inpatient unit is located in the NYS Psychiatric Institute which is adjacent to the Columbia Medical Center in northern Manhattan. Our new building for the NYS Psychiatric Institute is about 10 years old so the inpatient unit is quite attractive with beautiful views of the Hudson River and the Palisades. There is no financial cost for the inpatient stay nor is there a financial cost for participating in this study.