The persistent use of doses in excess of recommended levels is associated with increased risks of adverse reactions without evidence of additional benefits. Such treatment modality was evaluated in hospitalized psychiatric patients. During a 6-year recruitment period, a consecutive series of psychiatric inpatients receiving antipsychotic therapy were included. At admission, sociodemographic and clinical data, including antipsychotic drug use, were collected, and the 18-item version of the Brief Psychiatric Rating Scale was administered. At discharge, data on antipsychotic drug therapy were collected. Prescribed daily doses were converted into multiples of the defined daily doses. Using a cut-off score of a prescribed daily dose/defined daily dose as a ratio of more than 1.5 both at admission and at discharge assessments, a total of 62 (15.4%) patients persistently received high antipsychotic dose. With less stringent criteria (prescribed daily dose/defined daily dose as a ratio of more than 2), however, only 4.4% of the entire sample was persistently exposed to high antipsychotic doses. Bootstrapped linear regression analysis revealed that positive symptoms were positively associated with high antipsychotic dose, whereas negative symptoms were negatively associated with high antipsychotic dose. Antipsychotic polypharmacy at admission was the strongest predictor of persistently receiving antipsychotic doses in excess of recommended levels. This study showed that the use of high antipsychotic dosing is not an occasional event. Clinicians should consider that concurrent prescribing of two or more antipsychotic agents increases the probability of administering excessive dosing in the long-term.