Original Research

Assessing Refill Data Among Different Classes of Antidepressants

Fed Pract. 2019 October;36(6):S32-S37

References

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9. US Department of Veterans Affairs, Office of Mental Health Operations. Clinical support portal. User Guide – antidepressant non-adherence report (MDD43h MDD47h). https://spsites.cdw.va.gov/sites/OMHO_PsychPharm/_layouts/15/WopiFrame.aspx?sourcedoc=/sites/OMHO_PsychPharm/AnalyticsReports/UserGuideMDD43H47H.pdf. Accessed July 29, 2018. [Nonpublic site]

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Substance Use Disorder Influence

A significantly greater proportion of patients had an SUD in the low MPR group, suggesting that an SUD diagnosis may be a risk factor for low adherence. This finding is consistent with previous studies that also found that an SUD was associated with poor medication adherence.¹ Patients with depression and an SUD have been shown to have suboptimal outcomes compared to those without an SUD, including a lower response to antidepressant therapy and increased illness severity.^11,12

In a study of 131 outpatients with dual diagnosis (26% with depression) predictors for low self-reported adherence were a medication-related variable (increased adverse effects), a cognitive variable (low self-efficacy for drug avoidance), and a social factor (low social support for recovery). This variety of predictors seems to indicate that simple memory aids may not improve adherence. “Dual focus” mutual aid groups that provide social support for patients with dual diagnosis have been shown to improve adherence.¹³

The MEDVAMC Substance Dependence Treatment Program (SDTP) is an outpatient program that uses group education to aid veterans, often those with comorbid psychiatric disorders, to build relapse prevention skills and provide social support. Further exploration into the relationship between involvement in SDTP groups and antidepressant adherence in patients with dual diagnosis may be warranted.

Secondary Outcomes

Trends identified in the secondary outcome were similar to outcomes of previous studies: younger age, lower therapy involvement, and more comorbid psychiatric diagnoses were associated with lower adherence.^1,7,8 The presence of increased previous use of antidepressants in the low adherence group may suggest that these patients have an increased illness severity, although objective scales, such as the Patient Health Questionnaire 9 (PHQ9), were not consistently conducted and therefore not included in this analysis. It is unknown whether the previous antidepressant prescriptions were of adequate duration. These patients may have also had intolerances that led to multiple different antidepressant prescriptions and self-discontinuation.

The average MRCI of study patients was 13.5 (range 2 - 53), which was significantly lower than a previous study of geriatric patients with depression reporting an average MRCI of 25.4 (range 6 - 64).¹⁴ The positive trend between MRCI and adherence seen in this study was puzzling and counterintuitive. A more complex regimen is generally thought to be associated with poor adherence. Patients with a greater number of comorbid conditions may inherently be on more medications and thus have a more complex medication regimen. Manzano-Garcia and colleagues identified a negative relationship between adherence and the number of comorbidities (OR, 1.04-1.57; P = .021) and the MRCI (OR, 1.14-1.26; P < .001) in patients with HIV.¹⁵ Further studies are needed to clarify the relationship between medication adherence and medication regimen complexity in patients with mental health disorders. A better understanding of this relationship could possibly facilitate improved individualized prescribing practices and follow-up.

Limitations

Findings from our study should be interpreted within several limitations. Generalizability and statistical power were limited due to the small sample size, a practice site limited to 1 facility, and population type. The retrospective design of the study introduces inherent bias that would be minimized had a prospective study been conducted. The primary outcome was based upon MPR, which only accounts for refills within a specified time period and does not assess for actual or accurate use of the medication. Data collection was limited to VA and US Department of Defense records.