Recently it was shown that a commonly available antibiotic (ceftriaxone) has the unique neuroprotective function of decreasing the amount of extracellular glutamate in nervous system tissue by increasing the number of glutamate transporter proteins. Our clinical experience with patients who have refractory psychosis and past Lyme disease indicates that in some patients psychosis may improve with IV ceftriaxone therapy. Whether this improvement was due to its antimicrobial or glutamate effect or a placebo effect is uncertain. In a placebo-controlled design, this study investigates the ability of ceftriaxone to decrease psychotic symptoms in patients with refractory psychotic disorders. In addition, the study will examine glutamatergic functional activity before and after treatment using brain imaging with magnetic resonance spectroscopy.