Adherence to Medication Under Mandatory and Voluntary Mail Benefit Designs

Study Questions:

Are there differences in medication adherence rates under voluntary and mandatory pharmacy mail benefit designs?


A matched retrospective cohort study of adherence rates in the first year of therapy was conducted by comparing voluntary and mandatory mail cohorts. Inclusion criteria were individuals who initiated statin, angiotensin-converting enzyme (ACE) inhibitor, angiotensin-receptor blocker (ARB), platelet aggregation inhibitor, metformin, glitazone, or sulfonylurea therapy at a retail pharmacy between January 1 and March 31, 2009. Initiators in mandatory mail plans were matched on therapeutic class, age, sex, prospective risk, and cost of initial prescription with those in voluntary mail plans. Logistic regression models of optimal adherence were constructed to adjust for measured confounders.


Persistence rates were similar through the first 60 days of therapy. The mandatory mail cohort had a notable drop in persistence by day 90 (63.3% vs. 56.3%, p < 0.001), with a more pronounced drop among those without previous mail-service pharmacy use (50.5%). Median medication possession ratio (49.2% vs. 57.4%) and optimal adherence (33.6% vs. 36.1) were also lower. In the multivariable models, mandatory mail participants were less likely to achieve optimal adherence overall (odds ratio [OR], 0.70; 95% confidence interval [CI], 0.67-0.74) and in the metformin (OR, 0.55), sulfonylurea (OR, 0.72), ACE inhibitor (OR, 0.74), ARB (OR, 0.69), and statin (OR, 0.69) classes. Participants with no prior use of mail-service pharmacy had significantly lower odds of achieving optimal adherence in all therapeutic classes.


Mandatory mail appears to cause some members to discontinue therapy prematurely, particularly those without previous mail service pharmacy experience.


The findings are not surprising and should have been considered by the insurer and employer whose intentions were to reduce costs and improve compliance with the specific drugs studied. The authors noted that when members choose to discontinue rather than switch pharmacy channels, the unintended consequence is a reduction in medication adherence and the potential for increased medical expenses.

Keywords: Sulfonylurea Compounds, Medication Adherence, Pharmaceutical Services, Pharmacies, Postal Service

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