tokens: To determine if routine risperidone treatment is associated with a unique degree of D2 receptor occupancy and pattern of clinical effects , we used [ 123I ] IBZM SPECT to determine D2 occupancy in subjects treated with routine clinical doses of risperidone ( n = 12 ) or haloperidol ( n = 7 ). Both risperidone and haloperidol produced D2 occupancy levels between approximately 60 and 90 % at standard clinical doses .