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Delayed Onset of Drug Effects

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Encyclopedia of Psychopharmacology
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Delayed onset of action


According to the theory of delayed onset of action, the effects of antipsychotic or antidepressant drugs occur only after a delay of several weeks.

Current Concepts and State of Knowledge

The Concept

This chapter deals with the “delayed onset of action” hypothesis of antipsychotic and antidepressant drugs. This old theory states that antipsychotic or antidepressant drugs do not start to improve the symptoms immediately after administration, but that it rather takes several weeks until their effect sets in. It is shown that the “delayed onset of action” hypothesis is a myth and that the onset of action is early if not immediate. This article focuses on the evidence of antipsychotic drugs, but similar findings on antidepressants are briefly summarized at the end.

Historical Background

This theory probably emerged in the early 1970s, but there is no single author who could be quoted as its inventor and the statements in early textbooks were...

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Correspondence to Stefan Leucht .

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Leucht, S. (2010). Delayed Onset of Drug Effects. In: Stolerman, I.P. (eds) Encyclopedia of Psychopharmacology. Springer, Berlin, Heidelberg.

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