Clinical trial outcomes are heavily influenced by the non-naturalistic clinical trial process. Observations of outcomes in clinical practice are a valuable adjunct to clinical trial results.

Our null hypothesis was that clinically indicated switching to paliperidone palmitate had no effect on hospital admissions or hospital bed days.

This was a part-prospective mirror image study examining outcomes 2 years before starting paliperidone palmitate and 2 years after. Sensitivity analyses examined the effect of different placings of the mirror in the mirror image design.

We prospectively followed-up 225 patients prescribed paliperidone palmitate in clinical practice. At 2 years, 41.8% of patients were still receiving paliperidone palmitate. In the primary analysis, the mean number of admissions fell from 1.80 in the two years before starting paliperidone palmitate to 0.81 in two years following the drug’s initiation (outpatients) or two years following hospital discharge (inpatients) (P < 0.001). More than half of patients were not admitted to hospital during two years follow-up. Mean total bed days was reduced from 79.6 in the two years before to 46.2 in the two years after paliperidone palmitate initiation or discharge (P < 0.001). Sensitivity analyses gave broadly similar outcomes. Continuers demonstrated better outcomes than discontinuers in sensitivity analyses but not in the primary analysis.

Paliperidone palmitate initiation is associated with a substantial reduction in hospital admissions and days spent in hospital. The reduction in costs associated with reduced use of health care facilities is likely to exceed the purchase and administration costs of the drug.