Medication nonadherence and treatment outcome in patients with schizophrenia or schizoaffective disorder with suboptimal prior response.
OBJECTIVE
To examine the impact of medication nonadherence on treatment outcome in schizophrenia and potential risk factors for nonadherence.


METHODS
A post hoc analysis of a randomized, double-blind, 8-week, fixed-dose study comparing olanzapine 10, 20, and 40 mg/day for patients with schizophrenia or schizoaffective disorder (DSM-IV criteria) with suboptimal response to current treatment (N = 599) was conducted between September 12, 2003, and November 3, 2005, at 55 study centers in the United States. Nonadherence was defined as not taking medication as prescribed based on daily pill counts. Because there was no significant difference in nonadherence between dose groups, effects of nonadherence on efficacy and safety outcomes were examined using all 3 groups combined. Baseline demographics and symptom severity were investigated as potential risk factors for nonadherence.


RESULTS
During the 8-week study, 34.5% of patients were nonadherent at least once. Nonadherent patients had significantly less improvement compared to adherent patients as measured by change in Positive and Negative Syndrome Scale total score (-22.57 vs. -26.84, p = .002). Longer duration of nonadherence was associated with reduced likelihood of treatment response (odds ratio = 0.94, 95% CI = 0.90 to 0.99, p = .008). The early treatment discontinuation rate was higher in nonadherent compared to adherent patients (40.8% vs. 24.5%, p < .001). Adherent and nonadherent patients had comparable outcomes in most safety measures, except for weight change, for which adherent patients had greater weight gain than nonadherent patients (2.63 kg vs. 1.96 kg, p = .02). Greater depression severity at baseline (p = .01) and greater hostility level during the study were significant risk factors for nonadherence (p = .02).


CONCLUSIONS
Medication nonadherence had a significantly negative impact on treatment response, highlighting the importance of adherence to achieve satisfactory treatment outcome. Findings may also help clinicians identify patients at risk for nonadherence and utilize interventions to improve adherence.


BACKGROUND
clinicaltrials.gov Identifier: NCT00100776.
Lindenmayer
Jean-Pierre
JP
New York University School of Medicine, New York, N.Y. 10035, USA. lindenmayer@nki.rfmh.org
Liu-Seifert
Hong
H
Kulkarni
Pandurang M
PM
Kinon
Bruce J
BJ
Stauffer
Virginia
V
Edwards
Sara E
SE
Chen
Lei
L
Adams
David H
DH
Ascher-Svanum
Haya
H
Buckley
Peter F
PF
Citrome
Leslie
L
Volavka
Jan
J
D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use; D001569:Benzodiazepines / Q000627:therapeutic use; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D055118:Medication Adherence; D000077152:Olanzapine; D010352:Patient Dropouts / Q000706:statistics & numerical data; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000188:drug therapy*; D012008:Recurrence; D012559:Schizophrenia / Q000188:drug therapy*; D012720:Severity of Illness Index; D016896:Treatment Outcome
D014150:Antipsychotic Agents; D001569:Benzodiazepines; D000077152:Olanzapine