<p>The mechanism of action of Quetiapine, as with other drugs having efficacy in the treatment of schizophrenia and acute manic episodes associated with bipolar disorder, is unknown. However, it has been proposed that this drug&#39;s efficacy in schizophrenia is mediated through a combination of dopamine type 2 (D2 ) and serotonin type 2 (5HT2) antagonism. Antagonism at receptors other than dopamine and 5HT 2 with similar receptor affinities may explain some of the other effects of Quetiapine. Quetiapine&#39;s antagonism of histamine H1 receptors may explain the somnolence observed with this drug. Quetiapine&#39;s antagonism of adrenergic &alpha;1 receptors may explain the orthostatic hypotension observed with this drug.</p>