Evaluation of factors associated with medication adherence in patients with bipolar disorder using a medication event monitoring system: a 6-month follow-up prospective study

Background Non-adherence in patients with bipolar disorder (BD) results in symptoms, such as aggravation, BD recurrence, emergency room visits, re-hospitalization, and poor psychosocial outcomes. Though non-adherence rates have been reported to range between 30-50% in patients with BD, the problem of adherence is often either overlooked by the physician or denied by the patient. An essential first step to enhancing medication adherence is to objectively estimate adherence. The Medication Event Monitoring System (MEMS), which is a pill bottle cap with a microprocessor, is an accurate device for assessing medication adherence. Using the MEMS, we aimed to measure medication adherence in patients with BD and evaluate the factors associated with and 6-month changes in medication adherence. Methods Participants with BD were recruited from the psychiatric outpatient clinic of the Korea University Guro Hospital. The medication adherence of each participant was assessed using the MEMS, a self-report, pill count, and clinician rating. MEMS-measured adherence was reassessed after 6 months. Patient demographics were recorded and clinical assessments were conducted. Data were analyzed using Kappa statistics and Pearson's correlation analysis. Results Of the 59 participants, 50 records were included in the analysis. Patient adherence and adherence rate assessed by the MEMS were lower than those assessed by the other measures. MEMS-measured adherence was correlated more closely with pill counts than with self-reports or clinician ratings. MEMS-measured adherence was negatively associated with prescription duration and the Brief Psychiatric Rating Scale-Affect Subscale Score. Six-month changes in MEMS-measured adherence were positively associated with attitude toward drugs and negatively associated with weight gain assessed by the Udvalg for Kliniske Undersogelser Side Effect Rating Scale. Conclusions Clinicians may have to consider the limited accuracy of self-reporting and clinician rating methods and exercise caution when assessing the medication adherence of patients with BD using these methods. Our findings may assist clinicians in the assessment and improvement of medication adherence in patients with BD and, consequently, may be useful for the treatment and prevention of BD recurrence.