BACKGROUND: Adherence is key to the effectiveness of glucose-lowering drugs (GLD). Phollow is a real-world evidence (RWE) tool based on a cohort of community pharmacy users from about 83% of the community pharmacies (CPs) in Portugal. It allows the study and characterization of patients undergoing treatment with prescription drugs.

OBJECTIVES: To measure therapeutic adherence to antidiabetics, at the INN-level, in the real-world setting in Portugal.

METHODS: This is a retrospective, multicenter, cohort of patients taking blood glucose lowering drugs (GLD, excluding insulins), identified in Portuguese CPs. An anonymized random sample of 10% of all GLD-treated patients was selected from the Phollow cohort. Dispense data was retrieved between jan2018 to dec2021 through the CP software. The defined daily dose (DDD) was used to calculate number of days with drug supply. Age was calculated at the time of cohort entry. Adherence was defined as the proportion of days covered (PDC) at 1, 2, and 3 years for each INN.

RESULTS: 150,914 patients were included in this study. The median age was 66 years (IQR, 57.0-75.0), and 51.5% were female. Over the 4-year period, 71.2% used metformin, 13.7% used gliclazide, and 12.4% used metformin + sitagliptin at least once. The mean adherence (PDC) varied between 29.2% (acarbose) and 73.8% (glimepiride) in the first year of exposure, decreasing to 25.5% and 67.0% at 2-years, and to 23.7% and 64.0% at 3-years. The proportion of patients adherent to metformin (PDC ≥ 80%) was 12.5% at 1-year, 10.7% at 2-year, and 10.3% at 3-year.

CONCLUSIONS: Adherence varied substantially between INNs and generally decreased over time. There is a low proportion of patients adherent to first-line diabetes treatment (metformin). This may suggest some level of nonadherence, but also medication switches before completing a full year of treatment. Further research accounting for treatment switches is needed.