BACKGROUND: This study evaluated the influence of concomitant calcium channel blocker (CCB) and antipsychotic (AP) therapy on efficacy measures in patients with schizophrenia.
METHODS: Data from the Clinical Antipsychotic Trials of Intervention Effectiveness in Schizophrenia study were used to evaluate the effect of concomitant CCB therapy on the Clinical Global Impression-Severity (CGI-S) score, Positive and Negative Syndrome Scale (PANSS) score, and time to all-cause discontinuation of AP treatment. Concomitant treatment participants (CCB plus AP) were matched with controls (AP alone) by propensity scores using a 3:1 greedy match algorithm, then analyzed using a mixed linear effects model adjusted for fixed covariates.
RESULTS: The least squares mean change in CGI-S scores revealed a significant time-by-treatment interaction term, with greater improvements for the concomitant treatment group (P = .03). Total PANSS score showed no significant difference between groups at various time periods (1, 3, 6, 9, 12, 15, and 18 months) and time to all-cause discontinuation was also similar (hazard ratio 0.94, P = .73).
CONCLUSIONS: Improvements in CGI-S scores over time suggest that concomitant CCB plus AP treatment may reduce severity of illness more than AP treatment alone. However, PANSS score and time to all-cause discontinuation of AP treatment did not demonstrate improved outcomes.