The "delayed onset" of antipsychotic action--an idea whose time has come and gone.

For years, it has been known that the "onset" of the antipsychotic response is "delayed," and this notion is expressed in many major textbooks, informs clinical decisions and has even led to the search for biological markers responsible for this delayed onset. But is the onset of antipsychotic action really delayed? In this review, we bring together data from several recent studies of antipsychotic drugs that show that the onset of the antipsychotic effect is within the first day; the effect is distinguishable from behavioural sedation; is specific to antipsychotic drugs; is seen with oral and parenteral preparations; and is seen with typical and atypical antipsychotics. More anti- "psychotic" improvement is seen within the first 2 weeks than in any other 2-week period thereafter, and more improvement is seen in the first month than in the rest of the year of follow-up. This body of data convincingly refutes the notion of "delay" in the onset of antipsychotic action and suggests an "early" onset instead. The implications of this finding for clinical decision-making, mechanisms of antipsychotic action and drug discovery are discussed.