Major Finding: Treatment nonadherence is behind dose escalation in one-third of patients who receive antidepressant therapy.
Data Source: A large-scale analysis of patient nonadherence to chronic antidepressant therapy and subsequent prescribed dose escalation of the same medication using a national patient claims administrative database.
Disclosures: Medco Health Solutions Inc. provided funding for the study. Dr. Muzina became an employee of Medco Neuroscience Resource Center after the study began and received no compensation for his participation.
BOSTON – Nearly one-third of patients on antidepressant pharmacotherapy in a large-scale analysis did not take their original antidepressant dose as prescribed within the 6 months prior to dose escalation, a study has shown.
The findings suggest that the lack of adequate treatment response that drives dosage increases in many patients may be linked to suboptimal medication adherence rather than to dose insufficiency, Dr. David J. Muzina reported at the institute.
To evaluate patient nonadherence to chronic antidepressant therapy and a resulting upward dosage titration of the same medication, Dr. Muzina of Medco Health Solutions Inc. and his colleagues identified 53,530 patients from Medco's administrative patient claims database who were on antidepressant medications at the same dosage level for at least 6 months, followed by a subsequent submission of claims for a higher dose.
Patients with only one claim for antidepressant medicine in a 6-month period were excluded from the analysis, as were those taking multiple antidepressants.
To measure adherence status – determined by the proportion of days the patient possessed a supply of the medication, or the medication possession ratio (MPR) – a minimum of two claims for the same antidepressant drug was required. According to the National Committee for Quality Assurance's antidepressant performance measures, adherence was defined as an MPR of at least 80%.
The study cohort was predominantly female (72%), with a mean age of 51 years. More than two-thirds of the sample (68%) filled their antidepressant prescriptions at retail pharmacies, and 62% received generic medications, Dr. Muzina said. Most of the prescriptions were ordered by nonpsychiatrists, with only 15% ordered by psychiatrists; nearly half of the 49,524 patients for whom Chronic Disease Scores (CDS) were available had scores indicating a high degree of comorbidity.
Nearly 30% of the full cohort were nonadherent, Dr. Muzina reported. Among the nonadherent patients, “one in four was in possession of their prescribed medication during less than 3 months of the 6-month period,” he said.
An analysis of medication adherence by study subgroup – including age, sex, comorbidity, pharmacy channel (mail vs. retail), formulation (brand vs. generic), and prescriber (psychiatrist vs. nonpsychiatrist) – showed significant differences for all but the type of clinician prescriber. Regarding pharmacy channel and formulation, 19.2% of patients who filled prescriptions by mail were nonadherent, significantly lower than the 34.6% of those who used a retail pharmacy. Those receiving generic-only drugs had a small but significantly higher nonadherence rate (30.2%) than the 28.9% rate among patients receiving brand-name drugs.
Older age, male sex, and a higher CDS – perhaps due to increased interaction with clinicians needed by sicker patients – were also associated with significantly improved adherence, he said.