Rate of non-adherence prior to upward dose titration in previously stable antidepressant users

BackgroundNon-adherence to antidepressant medications is a contributing factor to disease relapse and may result in needless increases in antidepressant dosing.MethodsWe analyzed de-identified patient claims data from Medco Health Solutions, Inc.'s information database and measured adherence as the medication possession ratio (MPR), with adequate adherence as MPR ≥ 80%. Adherence was calculated for patients in whom antidepressants were dose escalated and who were on the same antidepressant medication for at least 180 days before the upward dosage titration. Statistical analysis was performed on subgroups comparing adherence with mail vs. retail channels, differences in age and gender, generic prescription vs. brand only, and prescription by psychiatrist vs. non-psychiatrist.Results29.7% of patients were non-adherent to their antidepressant medication during the 6 months prior to a prescribed increase in dosage. Non-adherence was significantly lower among patients using the Medco Therapeutic Resource Centers® mail order vs. retail channel. Younger age correlated with poorer adherence. Rates of non-adherence were also significantly greater among women, those receiving generic medications, and among patients with overall lower disease comorbidity. Adherence was not significantly impacted by prescription from a psychiatrist or a non-psychiatrist.LimitationsRetrospective design and use of an administrative patient claims database.ConclusionsSuboptimal medication adherence commonly precedes an upward dosage titration of antidepressant medications. Utilization of a mail order channel may improve adherence. Clinicians prescribing antidepressants should explore adherence issues carefully prior to recommending an increase in dosage.