In this study, patients receiving a stable twice-daily dose of generic clozapine formulation for the past one month will be switched to FazaClo. A trough steady-state clozapine and desmethylclozapine concentrations will be taken thrice while patient is on generic Clozapine. After the third clozapine level patients will be switched from their generic clozapine formulation to FazaClo, at the same dosage and treatment regimen as the generic clozapine formulation they had been receiving. Trough steady-state clozapine and desmethylclozapine concentration levels will be taken twice, 7 days and 14 days after starting Fazaclo.