Differences in Medication Adherence and Healthcare Resource Utilization Patterns

Background: Given the number of antidepressants available and their rising costs, healthcare payers have initiated restrictive reimbursement policies for newer antidepressants, without consideration for differences in their effectiveness or tolerability.

Objective: The objective of this study was to comprehensively compare medication adherence rates and associated healthcare utilization costs for patients using later-generation versus earlier-generation antidepressants in a managed care setting. Antidepressants launched after 2002 were deemed third-generation antidepressants, while antidepressants available prior to 2002 were deemed first-generation (TCAs and MAOIs) and second-generation (serotonin and noradrena-line [norepinephrine]-dopamine reuptake inhibitors).

Study design: Retrospective database analysis using medical and pharmacy data from over 75 managed care plans covering 55 million lives.

Setting/patients: All patients receiving an antidepressant between 1 January 2002 and 30 September 2004 were identified. The index date for patients was the date of their first antidepressant prescription within this time period. Patients had to (i) have a diagnosis of depression or anxiety disorder, or depression and anxiety disorder within 6 months prior to or 30 days after their index prescription; (ii) be at least 18 years of age, without having taken antidepressant therapy for 6 months prior to their index date; and (iii) be continuously eligible for 6 months prior to their index date and during their 6-month follow-up period. Patients were excluded if they had a diagnosis of psychosis-related disease, Alzheimer’s or Parkinson’s disease, or were initiated on psychosis-related medications.

Intervention/main outcome measure: Patients meeting selection criteria were followed for 6 months to assess rates of antidepressant adherence, therapy change rates and medical healthcare costs.

Adherence: Of patients receiving third-generation antidepressants, 33.6% were adherent compared with 29.3% and 12.4% of patients receiving second- and first-generation antidepressants, respectively. Newer agents also had better adherence rates across all diagnostic cohorts. After adjusting for baseline differences, the odds of being adherent to therapy were significantly lower for those taking second- and first-generation agents versus newer antidepressants. Among the newer agents, the proportion of patients adherent to their therapy was: venlafaxine extended release 38%, paroxetine controlled release (CR) 35%, escitalopram 34%, duloxetine 32% and bupropion extended release (XL) 31%.

Healthcare utilization: Of the patients taking older antidepressants, 13% (second generation) and 21% (first generation) were hospitalized at least once for any reason compared with 12% of patients taking newer agents. Overall, the odds of all-cause hospitalization within 6 months of therapy initiation were significantly higher for patients taking older antidepressants. Among the newer agents, hospitalization rates ranged from 15.9% for duloxetine to 12.5% for paroxetine CR and bupropion XL. The unadjusted 6-month total medical costs (not including pharmacy costs) per patient were $US3514 for second-generation, $US5744 forfirst-generation and $US3284 for newer antidepressants. After controlling for baseline differences, patients receiving second- and first-generation antidepressants incurred 12% and 44% higher costs, respectively. The unadjusted 6-month medical costs for the newer agents ranged from $US2715 for paroxetine CR to SUS6042 for duloxetine.

Conclusion: The results of this study provide essential information for healthcare decision makers about the potential advantages of newer generation antidepressants versus older generation antidepressants, as well as the differences between the specific newer agents, with respect to improved rates of adherence and therapy change, reduced hospitalizations and healthcare costs.