Mail-order pharmacy users were more likely than local pharmacy users to have a financial incentive to fill their prescriptions (49.6 percent vs. 23.0 percent) and to live a greater distance from a local pharmacy (8.0 miles vs. 6.7 miles). An example of a financial incentive is receiving a three-month supply of medication for the cost of a two-month supply.

After adjusting for other variables, whites were more likely to use mail-order pharmacies (24.1 percent) than were Asian/Pacific Islanders (8.4 percent), Hispanics (5.2 percent), African Americans (4.0 percent) and individuals of mixed race (8.0 percent).

While other research has examined the association between medication costs and mail-order and local pharmacies, this is the first study to look at the relationship between pharmacy type and medication adherence. Furthermore, it controls for differences in out-of-pocket costs and medication supply (by number of days) between mail-order and local pharmacy users, something other datasets have not included.

"In other words, our study is able to isolate the use of mail-order pharmacies specifically, without the results being affected by differences in cost or in the number of pills provided with each dispensing," Duru said.

The study does have some limitations. For example, the findings need to be confirmed by a randomized controlled trial.

Still, the research suggests that increased mail-order use to obtain medications could improve patients' adherence.

Source: Kaiser Permanente Division of Research