The purpose of this study is to determine the efficacy (how well the drug works), safety, and side effects of paliperidone palmitate injection compared to placebo in the treatment of the symptoms of schizophrenia in adults. The placebo used in this study was a nutritional substance known as 20% Intralipid emulsion given to patients requiring intravenous feedings.

Paliperidone palmitate is an aqueous suspension that releases paliperidone gradually over a period of about 1 month and is under development to provide a sustained and stable level of paliperidone. This is a randomized (patients will be assigned to different treatment groups based solely on chance), double-blind (neither the patient nor the physician will know if placebo or drug is being given and at what dose), placebo-controlled, multicenter study in patients with schizophrenia. The study consists of a screening period (maximum 5 days, including a 3-day washout of psychotropic medications other than antidepressants, if applicable); a 7-day, open-label, oral run-in period; and a 64-day double-blind treatment period. The total duration of the study is approximately 11 weeks. Efficacy will be evaluated during the study using the Positive and Negative Symptom Scale for Schizophrenia (PANSS) and the Clinical Global Impression - Severity (CGI-S) scale. Safety will be evaluated by monitoring adverse events and changes in clinical laboratory results, including prolactin levels; physical examination results; tardive dyskinesia will be rated using the Abnormal Involuntary Movement Scale (AIMS), akathisia will be rated according to the Barnes Akathisia Rating Scale (BARS), extrapyramidal symptoms will be evaluated using the Simpson-Angus Rating Scale (SAS); electrocardiogram (ECG); vital sign measurements; and concomitant therapy. ER OROS paliperidone (6 or 12 mg) or IR paliperidone (2 or 4 mg) oral dosage administered daily for 7 days (Day -7 to -1), followed by i.m. injections of paliperidone palmitate (either 50 mg eq. or 100 mg eq.), or placebo on Days 1, 8, and 36 of the study.

Inclusion Criteria:

• Patients diagnosed with schizophrenia
• for at least 1 year before screening
• meet PANSS score criteria
• must agree to hospitalization for a minimum of 14 days
• body mass index (BMI) <35.0 kilogram (kg)/meter (m)2.

Exclusion Criteria:

• Patients who are involuntarily committed as in-patients
• have a DSM-IV Axis I diagnosis other than schizophrenia
• have a DSM-IV diagnosis of substance dependence within 3 months before screening (nicotine, caffeine dependence, and history of recreational use of marijuana are not exclusionary)
• have a decrease of >/=25% in the PANSS score between screening and predose
• previous lack of response to 2 adequate trials of antipsychotic treatment
• have a significant risk of suicidal, homicidal, or violent ideation or behavior
• have severe gastrointestinal narrowing (pathologic or iatrogenic)
• current presence of any significant or unstable medication condition
• treatment with any protocol disallowed therapies
• clinically significant result from screening laboratory or ECG.