Hayden Stewart is a Pharmacy Resident and Saadia Basit is a Clinical Pharmacy Specialist in Mental Health, both at Michael E. DeBakey Veterans Affairs Medical Center in Houston, Texas. Correspondence: Hayden Stewart (hayden.stewart@va.gov)
Author disclosures The authors report no actual or potential conflicts of interest with regard to this article.
Disclaimer The opinions expressed herein are those of the authors and do not necessarily reflect those of Federal Practitioner, Frontline Medical Communications Inc., the US Government, or any of its agencies. This article may discuss unlabeled or investigational use of certain drugs. Please review the complete prescribing information for specific drugs or drug combinations—including indications, contraindications, warnings, and adverse effects—before administering pharmacologic therapy to patients.
Information collected for the primary outcome, including antidepressant class and MPR, was obtained from the Antidepressant Nonadherence Report. For the secondary outcome, the following data was collected for each patient: age, gender, race, housing status, Medication Regimen Complexity Index (MRCI), number and type of psychiatric diagnoses, number of previous antidepressants, psychotherapy involvement, and number of mental health visits during the 3-month study period. The MRCI is an objective, validated tool that determines relative medication regimen complexity by taking into consideration the number of medications, route and frequency of administration, splitting/multiple dosage units, and presence of any special instructions.11
The primary outcome was tested using a one-way analysis of variance (ANOVA). Nominal secondary outcomes were analyzed using the Fisher’s Exact. Continuous secondary outcomes were examined using an unpaired t-test.
Results
Of 320 charts, 212 patients were excluded and 108 were included (Figure). The most common reason for exclusion was a previously prescribed antidepressant. Of the included patients 49 had an MPR ≥ 80% and 24 had an MPR ≤ 60%. The characteristics of the study population are found in Table 1 and the antidepressant frequencies and MPRs are included in Table 2.
About 87% of study patients had a diagnosis of depression. Other concomitant psychiatric diagnoses include posttraumatic stress disorder (PTSD), anxiety, insomnia, and 2 cases of intermittent explosive disorder. There were no significant differences in mean MPR between the antidepressant classes (P = .31). Within each drug class, we identified the proportion of patients with high adherence (MPR ≥ 80%). Bupropion had the greatest percentage of highly adherent patients (50%) compared with SSRIs (42.5%), SNRIs (38.5%), and mirtazapine (31.3%).
Table 3 compares the characteristics between high MPR and low MPR patients. The low MPR group showed a significantly greater proportion of patients with an SUD than the high adherence group (41.7% vs 10.2%, respectively; P = .04). The most common type of SUD was alcohol use disorder followed by cannabis use disorder. There were no other statistically significant differences identified between high and low MPR groups. There was a trend towards significance when comparing MRCI between the 2 groups (high MPR, 15.2; low MPR, 10.8; P = .06).
Discussion
In our study, there was no significant difference in 3-month adherence rates between veterans on SSRIs, SNRIs, bupropion, and mirtazapine. This result differs from a study by Keyloun and colleagues that found that SNRIs had a significantly higher adherence rate when compared with other antidepressants.7
SSRIs were the most commonly prescribed antidepressant in our study, and also had the greatest mean 3-month MPR. The high use of SSRIs may be due to the greater number of SSRI choices to select from compared with other classes. SSRIs may also have been selected more frequently because nearly half (45.4%) of the patients had comorbid PTSD, for which 3 of the 4 first-line treatment options are SSRIs (sertraline, paroxetine, fluoxetine).
As previously stated, Keyloun and colleagues previously found that SNRIs had the highest 3-month adherence rate in a study of > 5000 patients.7 In our study, SNRIs had the second highest mean 3-month MPR at about 75%, but the difference was not considered significant when compared with other antidepressant classes.
Bupropion was prescribed least frequently, but had the largest proportion of adherent patients. Gaspar and colleagues demonstrated similar outcomes, reporting that patients prescribed bupropion had a high OR for adherence.1 Bupropion may have had relatively low prescribing rates in our study because 64% of patients were diagnosed with a comorbid anxiety disorder and/or PTSD. For these patients, bupropion avoidance may have been intentional so as to not exacerbate anxiety.
Mirtazapine had both the lowest mean MPR and the lowest proportion of adherent patients. While no significant difference between antidepressant 3-month adherence rates were found, this study’s findings were similar to previous studies that found lower adherence to mirtazapine.1,5 Adverse effects such as sedation, increased appetite, and weight gain may have contributed to low adherence with mirtazapine.4 Patients may also have been using the agent on an as needed basis to treat insomnia despite the order being written for daily use.
