Second-generation (atypical) antipsychotics: The concept of “atypicality” is from the finding that the second generation antipsychotics (SGAs) had a greater serotonin/dopamine ratio than did earlier drugs, and might be associated with improved efficacy (particularly for the negative symptoms of psychosis) and reduced extrapyramidal side effects. Some of the efficacy of atypical antipsychotics may be due to 5-HT2 antagonism or the blockade of other dopamine receptors. Agents that purely block 5-HT2 or dopamine receptors other than D2 have often failed as effective antipsychotics.