Study of Preladenant for the Treatment of Neuroleptic Induced Akathisia (Study P05145)

Inclusion Criteria: * Participants or guardian must be willing to give written informed consent. * Part 1 Only: Participants with acute (not drug related) psychoses with a Positive and Negative Symptom Scale for Schizophrenia (PANSS) score of at least 60: schizophrenia, schizo-affective, schizo-manic, and acute mania with a history of previous treatment with neuroleptics. * Part 1 Only: Participants initiating haloperidol for the treatment of an acute psychotic episode at a dose of at least 7.5 mg per day. * Part 2 Only: Inpatient participants who have developed akathisia as a result of haloperidol at \>=5 mg per day for the treatment of acute psychosis. The enrollment of participants receiving other neuroleptics is allowed only after consultation and agreement by the sponsor. * Participants of either sex and of any race between the ages of 18 and 65 years, inclusive. * Participant's clinical laboratory tests (complete blood count \[CBC\], blood chemistry, and urinalysis) must be within normal limits or clinically acceptable to the investigator/sponsor. Participant's liver function test results (ie, aspartate aminotransferase \[AST\], alanine aminotransferase \[ALT\]) must not be elevated above the normal limits at Screening and on Day -1/1. * Participants must be free of any clinically significant disease other than psychosis that would interfere with the study evaluations. * Screening electrocardiogram (ECG) must be clinically acceptable to the investigator. * Female of ch…