Aim – To investigate the relation between medication-related factors and adherence in people with schizophrenia in outpatient treatment. Methods – The sample comprised 409 outpatients (ICD-10 diagnosis of schizophrenia) with clinician-rated instability in four European cities (Amsterdam, The Netherlands; Verona, Italy; Leipzig, Germany; London, Great Britain). Adherence was assessed using the Medication Adherence Questionnaire (patient perspective), and the Clinician Rating Scale (clinician perspective). Examined medication-related factors were type (atypical vs. typical), application (oral vs. depot), daily dose frequency of antipsychotic medication (Medication History Scale), number of side effects (Liverpool University Neuroleptic Side Effect Rating Scale), and patient attitudes toward medication (Drug Attitude Inventory). Multiple regression analysis was used to identify predictors of adherence by medication-related factors. Results – Adherence, as rated by patient and clinician, was predicted by patient attitude towards medication, but was unrelated to type of drug, formulation or side effects of antipsychotic medication. A high daily dose frequency was associated with better adherence, but only when rated by the patient. Conclusions – In order to improve adherence there is a need to seriously consider and attempt to improve patient attitude toward medication. However, type of antipsychotic and other medication-related factors may not be as closely related to adherence as it has often been suggested.
Declaration of Interest: The study was funded by a grant from the Quality of Life and Management of Living Resources Program of the European Union (QLG4-CT-2001–01734). JM, AS, CB, MK, CB, LB, and BP declare that they have not received any form of financing including pharmaceutical company support or any honoraria for consultancies or interventions during the last two years. DR has received honoraria from Eli Lilly, Janssen Cilag and Astra Zeneca for consultancy work, and Anita Patel has received research consultancy funding from Servier. TB reports research funding to the department from Astra Zeneca, GlaxoSmithKline and Affectis for clinical trials and investigator-initiated trials; the department has also received funds to a minor extent for symposia and in-house training from Astra Zeneca, Bristol-Myers Squibb, Eisai, Janssen Cilag, Lilly Germany, Lundbeck, Novartis, Pfizer, Servier, and Wyeth. All authors declare that they have no other involvements that might be considered a conflict of interest in connection with this article.