In a psychotic patients they reduce irrational behaviour, agitation and aggressiveness and controls psychotic symptoms. Disturbed thought and behaviour are gradually normalised, anxiety is relieved. Hyperactivity, hallucinations and delusions are suppressed.

All phenothiazines, thioxanthenes and butyrophenones have the same antipsychotic efficacy, but potency differs in terms of equieffective doses. The aliphatic and piperidine side chain phenothizines (chlorpromazine, triflupromazine, thioridazine) have low potency, produce more sedation and cause greater potentiation of hypnotics, opioids etc. The sedative effect is produced immediately while antipsychotic effect takes weeks to develop. Moreover, tolerance develops to the sedative but not to the antipsychotic effect. Thus, the two appear to be independent action. Performance and intelligence are relatively unaffected but vigilance is impaired.

Extrapyramidal motor disturbances initialy linked to the antipsychotic effect but are more prominent in the high potency compounds and least in thioridazine. The effects comprise acute dystonias and tardive dyskinesia. A predominance of lower frequency waves occurs in EEG and arousal response is dampened. However, no consistent effect on sleep architecture has been noted. The disturbed sleep pattern in a psychotic is normalised.