Predictors of antipsychotic dose changes in the CATIE schizophrenia trial

Data from the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) was used with the objective of evaluating factors associated with antipsychotic dose changes. CATIE was a randomized, comparative effectiveness trial for patients with schizophrenia in which a clinician prescribed a double-blind, flexible dose of one of five antipsychotic medications. The mean number of capsules prescribed monthly was evaluated to identify the period following up-titration with the least sample attrition in which dose changes were likely in response to clinical factors. Demographic, efficacy and tolerability variables were evaluated in two regression models predicting a one capsule dose decrease or increase. The mean dose increased to 2.7 capsules over the first 3 months. The post-titration plateau was identified as between 3 and 6 months. Factors associated with dose increases included the Clinical Global Impression Scale at 6 months and change in the Positive and Negative Syndrome Scale between 3 and 6 months. Decreased dosing was associated only with lower patient rated at 6 months global impression of health. Neither tolerability measures, nor body weight was significantly associated with dose changes. In conclusion, dose changes were weakly associated with measures of current or changing clinical status and not affected by measures of side effects.