Medication adherence in a comparative effectiveness trial for bipolar disorder

Psychopharmacology remains the foundation of treatment for bipolar disorder, but medication adherence in this population is low (range 20-64%). We examined medication adherence in a multisite, comparative effectiveness study of lithium.

The Lithium Moderate Dose Use Study (LiTMUS) was a 6-month, six-site, randomized effectiveness trial of adjunctive moderate dose lithium therapy compared with optimized treatment in adult out-patients with bipolar I or II disorder (N=283). Medication adherence was measured at each study visit with the Tablet Routine Questionnaire.

We found that 4.50% of participants reported missing at least 30% of their medications in the past week at baseline and non-adherence remained low throughout the trial (<7%). Poor medication adherence was associated with more manic symptoms and side-effects as well as lower lithium serum levels at mid- and post-treatment, but not with poor quality of life, overall severity of illness, or depressive symptoms.

Participants in LiTMUS were highly adherent with taking their medications. The lack of association with possible predictors of adherence, such as depression and quality of life, could be explained by the limited variance or other factors as well as by not using an objective measure of adherence.