Adherence to multiple drug therapies: refill adherence to concomitant use of diabetes and asthma/COPD medication

Most patients are non-adherent with their medication sometimes, i.e. that they do not always use their medicines as prescribed. This might result in both under- and overuse and can lead to therapy failure, resulting in both unnecessary suffering and high costs. Therefore, medication adherence should be as high as possible. The aims of this thesis were to investigate the refill adherence to long-term drug treatment, especially for patients with asthma and chronic obstructive pulmonary disease (COPD), and to study treatment gaps for patients with undersupply and drug costs for patients with oversupply. Further aims were to compare different methods for assessing refill adherence and analyse whether the same patient has the same refill adherence pattern to two different chronic drug treatments, i.e. diabetes and asthma/COPD. The thesis shows that satisfactory refill adherence (80-120% of the prescribed dose) was 57% for repeat prescriptions with long-term drug treatment; undersupply was 21% and oversupply 22%. Patients with undersupply were without drugs more than half of the prescribed treatment time and the median oversupply for 90-100 days dispensation interval was 28 days. Patients who were exempt from charges had significantly higher oversupply than non-exempt patients and that leads to unnecessary cost for society. The level of satisfactory refill adherence for repeat prescriptions dispensed for asthma/COPD was on average 30%. The same low level was displayed for the elderly, where undersupply was more common than oversupply. Assessments of refill adherence during a one-year period gave the same results irrespective of whether the repeat prescriptions were from an individual pharmacy record database or were manually collected at a pharmacy.Patients with concomitant use of diabetes and asthma/COPD drugs do not have the same dispensation pattern for both drug types. The introduction of patient profiles as a new approach to complement the calculated refill adherence needs to be further studied in larger and more divergent populations. In the future, the new national pharmacy record database in Sweden has opened up for larger studies and will be valuable when studying patterns of drug utilization.