Medication adherence in patients with diabetes mellitus: does physician drug dispensing enhance quality of care? Evidence from a large health claims database in Switzerland

BACKGROUND The drug-dispensing channel is a scarcely explored determinant of medication adherence, which is considered as a key indicator for the quality of care among patients with diabetes mellitus. In this study, we investigated the difference in adherence between diabetes patients who obtained their medication directly from a prescribing physician (physician dispensing [PD]) or via a pharmacy. METHODS A retrospective cohort study was conducted using a large health care claims database from 2011 to 2014. Patients with diabetes of all ages and receiving at least one oral antidiabetic drug (OAD) prescription were included. We calculated patients' individual adherence to OADs defined as the proportion of days covered (PDC), which was measured over 1 year after patient identification. Good adherence was defined as PDC ≥80%. Multivariate logistic regression analysis was performed to assess the relationship between the PDC and the dispensing channel (PD, pharmacy). RESULTS We identified a total of 10,430 patients prescribed drugs by a dispensing physician and 16,292 patients receiving drugs from a pharmacy. Medication adherence was poor in both patient groups: ~40% of the study population attained good adherence to OADs. We found no significant impact of PD on the adherence level in diabetes patients. Covariates associated significantly with good adherence were older age groups, male sex, occurrence of comorbidity and combined diabetes drug therapy. CONCLUSION In conclusion, adherence to antihyperglycemic medication is suboptimal among patients with diabetes. The results of this study provide evidence that the dispensing channel does not have an impact on adherence in Switzerland. Certainly, medication adherence needs to be improved in both supply settings. Physicians as well as pharmacists are encouraged to develop and implement useful tools to increase patients' adherence behavior.