Multi-dose drug dispensing as a tool to improve medication adherence: A study in patients using vitamin K antagonists

Multi-dose drug dispensing (MDD) is a dosing aid that provides patients with disposable bags containing all drugs intended for 1 dosing moment. MDD is believed to increase medication adherence, but studies are based on self-reported data, and results may depend on socially desirable answers. Therefore, our purpose was to determine the effect of MDD on medication adherence in non-adherent patients taking vitamin K antagonists (VKAs), and to compare with instructing patients on medication use.

We conducted a before-after study in non-adherent patients where MDD was the exposure and change in adherence after MDD initiation was the outcome (within patient comparison). Time in therapeutic range (TTR) was selected as a measure for adherence, as this reflects stability of VKA treatment. To analyze whether MDD improved adherence as compared with standard care (ie, letters or calls from nurses of the anticoagulation clinic), non-adherent patients without MDD were also followed to estimate their TTR change over time (between patient comparison).

Eighty-three non-adherent VKA patients started using MDD. The median TTR was 63% before MDD and 73% 6 months after MDD. The within patient TTR increased on average by 13% (95%CI 6% to 21%) within 1 month after starting MDD and remained stable during the next 5 months. The TTR of MDD-patients increased 10% (95%CI 2% to 19%) higher as compared with non-MDD patients within 1 month but was similar after 4 months (TTR difference 3%, 95%CI -2% to 9%).

Adherence improved after initiation of MDD. Compared with instructing patients, MDD was associated with better adherence within 1 month but was associated with similar improvement after 4 months.