THE EFFICACY of psychoactive drugs in treating psychotic patients is often dependent on maintenance treatment for extended periods. Many psychotropic compounds exhibit short durations of action, making repeated daily administration necessary. Patients discontinue their medication, with frequent relapses and rehospitalizations for many reasons, including the sense of wellbeing, fear, neglect, lack of insight, poor judgment, delusions, disturbed communication, miscalculation of visits, or expense.1 In contrast to the physically ill who maintain treatment because they suffer from their symptoms, psychiatric patients, particularly schizophrenics, may have no such reminder. In the follow-up of one of our recent studies,2 one-fourth of the discharged patients were rehospitalized with active psychotic symptoms within four to eight weeks of a self-induced drug free period. To avoid discontinuation of medication, recurrence of psychosis, and rehospitalization, a longer acting psychotropic compound was needed, similar to depot insulin used in diabetes, and the development of such a compound among the phenothiazines was encouraged.