THE MECHANISM OF ACTION OF ARIPIPRAZOLE, AS WITH OTHER DRUGS HAVING EFFICACY IN SCHIZOPHRENIA, IS UNKNOWN. HOWEVER, IT HAS BEEN PROPOSED THAT THE EFFICACY OF ARIPIPRAZOLE IS MEDIATED THROUGH A COMBINATION OF PARTIAL AGONIST ACTIVITY AT D 2 AND 5-HT 1A RECEPTORS AND ANTAGONIST ACTIVITY AT 5-HT 2A RECEPTORS. ACTIONS AT RECEPTORS OTHER THAN D 2 , 5-HT 1A , AND 5-HT 2A MAY EXPLAIN SOME OF THE OTHER CLINICAL EFFECTS OF ARIPIPRAZOLE, E.G., THE ORTHOSTATIC HYPOTENSION OBSERVED WITH ARIPIPRAZOLE MAY BE EXPLAINED BY ITS ANTAGONIST ACTIVITY AT ADRENERGIC ALPHA 1 RECEPTORS. ARIPIPRAZOLE IS WELL ABSORBED, WITH PEAK PLASMA CONCENTRATIONS OCCURRING WITHIN 3 TO 5 HOURS. AT THERAPEUTIC CONCENTRATIONS, ARIPIPRAZOLE AND ITS MAJOR METABOLITE ARE GREATER THAN 99% BOUND TO SERUM PROTEINS, PRIMARILY TO ALBUMIN.