Using the Pharmaceutical Collection Database to identify patient adherence to oral hypoglycaemic medicines

INTRODUCTION Poor adherence to oral hypoglycaemic medicines is a key contributor to therapy failure and sub-optimal glycaemic control among people with type 2 diabetes. It is unclear how commonly non-adherence to oral hypoglycaemics occurs in the general population. This information is essential to design and implement local adherence strategies. AIM This study aimed to determine levels of sub-optimal adherence and identify patient groups who may need additional adherence support. METHODS The dispensing data of 340,283 patients from one District Health Board was obtained from the Pharmaceutical Collection Database for the period 2008-15. Of these, 12,405 patients received oral hypoglycaemic therapy during the study period. The proportion of days covered (PDC) was calculated for patients with complete data and a PDC value of ≥80% was used to indicate sufficient adherence. Patient demographics (gender, ethnicity, age, socioeconomic status) and therapy type (mono- or combination) were described. RESULTS Overall, 54.5% of the patients were found to have a PDC of <80% and so were considered non-adherent. Non-adherence was significantly higher in patients receiving combination oral hypoglycaemic therapy than monotherapy; in male patients; in New Zealand Māori patients; and in patients with higher socioeconomic deprivation. DISCUSSION In the study region, non-adherence to oral hypoglycaemic medicines was significant and widespread. Identification of such patients is important so that strategies to enhance adherence can be implemented. Prescribers need to be encouraged to optimise monotherapy before the addition of another oral hypoglycaemic, and adherence support services should be offered not only to older patients.