Our analysis is one of the first studies to examine the characteristics of patients using mail-order pharmacies. It confirmed that patients who received newly prescribed medications through the mail were more likely to have good adherence than patients who obtained them at local KPNC pharmacies. Although there is a paucity of literature in this area, our findings of a 7– to 8–percentage point increase in good adherence associated with mail-order use are consistent with a recent industry non–peer-reviewed study.29
That study compared adherence within a health plan that required members to use a mail-order pharmacy and another plan that required members to use a local pharmacy. The authors found that, compared with the use of a local pharmacy, the use of a mail-order pharmacy was associated with an 8.4–percentage point increase in good adherence to antiglycemic medications, a 7.8–percentage point increase in good adherence to antihypertensive medications, and a 6.8–percentage point increase in good adherence to lipid-lowering medications.
Inferences from observational studies are limited by biases not evident in randomized exposures. Self-selection is of particular concern when studying outcomes such as medication adherence because it may introduce unmeasured differences in patient characteristics. These characteristics could potentially be associated with adherence and result in spurious associations between adherence and pharmacy type. The results of the likelihood ratio test within a BVP model suggest that unmeasured patient self-selection into mail order did not significantly distort our findings. We also controlled for potential confounders not addressed in prior published analyses, including differences in days’ supply and out-of-pocket costs between mail-order and local pharmacies. Although we cannot conclusively determine a causal relationship, the association between mail-order use and medication adherence deserves further investigation with a randomized study design.
Our findings reinforce the importance of system-level determinants of patient behavior. In response to a prevailing attitude of blaming the patient for poor adherence, the World Health Organization30
has developed an adherence model that considers health system and socioeconomic factors, as well as patient-specific and medication-specific factors. Recent qualitative studies31,32
found that physicians rarely address system-level barriers to medication acquisition when prescribing a new medication. Physicians, nurses, or clinic-based support staff may be able to improve adherence when a new medication is prescribed by ensuring that patients who have efficient access to a reliable mail-order pharmacy system consider using it to obtain their refills.
Our findings also suggest the intriguing potential of larger organization-level interventions to improve adherence by promoting increased mail-order use. Recent review articles2,33
examining adherence intervention research take a despairing tone, noting that the field is “stuck,” without good options to move forward. Although there have been more than 50 randomized controlled trials of adherence interventions for chronic medications, none have evaluated efforts to minimize system-related barriers to medication acquisition.34,35
focused on intensive efforts by pharmacists to provide ongoing medication counseling and demonstrated improved adherence and better outcomes. However, such approaches are costly and typically are not compensated by third-party payers. In current clinical settings, counseling at the time of medication refills is uncommon.39,40
Although proven effective, adoption of intensive counseling protocols may require a major expansion of professional responsibilities and represent a significant additional expense for health plans or employers.
Developing effective strategies to increase mail-order pharmacy use could move the field of adherence intervention research in an important new direction. Our findings provide evidence supporting the development and evaluation of interventions to increase mail-order use. Although these interventions would not enhance existing levels of pharmacist counseling, they would potentially be appealing for several other reasons. Assuming similar generic dispensing rates across pharmacy type, mail-order pharmacies seem to be cost saving for a health system after the associated increase in medication use is taken into account.11,13
Many patients save money when ordering their medications by mail, and efforts to increase mail-order use among interested patients may be well accepted by patients and health systems. Interventions to increase mail-order use would, in many cases, take advantage of existing system infrastructure, further promoting sustainability. Many health systems, including the Department of Veterans Affairs,41
have well-established mail-order pharmacy systems that efficiently fill several million prescriptions per year.
Despite their potential benefits, interventions to increase mail-order pharmacy use would need to be carefully designed and implemented to avoid inadvertently harming patients. Such interventions should not come at the expense of face-to-face pharmacist time needed to clarify dosing schedules or check for adverse drug interactions, including dietary supplements or over-the-counter medications. Research studies that carefully assess the potential benefits and harms of increasing mail-order pharmacy use on a large scale are warranted.
Our study has several limitations. First, it was cross-sectional and cannot conclusively determine a causal relationship. Second, because of sample size limitations, we were unable to compare adherence among patients who use mail-order exclusively versus those who use local pharmacies exclusively. Third, we did not measure medication consumption, although our claims-based measure has been validated against pill counts.19
Fourth, the findings may not generalize to fee-for-service settings with less integrated medication delivery systems or to patients who do not have diabetes. Fifth, we measured adherence to a single medication rather than multiple medications taken simultaneously. Sixth, we measured adherence only up to 15 months after the first medication fill, so our findings may not reflect long-term changes in adherence.
In summary, refilling a newly prescribed diabetes-related medication by mail is associated with a greater likelihood of good adherence compared with refilling at a local pharmacy. Minority patients and patients of low socioeconomic status have particularly low rates of mail-order pharmacy use. Although our findings should be confirmed in a randomized clinical trial, encouraging the use of existing efficient mail-order pharmacies may represent a novel, low-cost, and sustainable approach to improve medication adherence.
In this study of an integrated delivery system, the use of mail-order pharmacies was associated with a higher likelihood of good medication adherence.
■ Minority patients and patients of low socioeconomic status were less likely to refill their medications by mail.
■ Although these findings should be confirmed in other analyses and in a randomized controlled trial, they suggest the intriguing potential of organization-level interventions to improve adherence, particularly among vulnerable populations, by promoting increased mail-order use.