OBJECTIVES: Over half of patients with chronic obstructive pulmonary disease (COPD) struggle to use a metered dose inhaler correctly. Strikingly, therapies seem to vary from country to country. For instance, the three strengths of a specific dry powder inhaler prescribed in Germany are consistently 20%/25% lower for their two active ingredients than the corresponding three strengths dispensed in the UK. This study attempts to quantify the impact of this difference on patient behaviour.

METHODS: To quantify adherence we used two comprehensive anonymised patient level datasets comprising 13,337 and 20,252 unique patient IDs for the UK and Germany, respectively. Each patient was followed for 365 days and a Medication Possession Ratio (MPR) trend calculated using the FMPR methodology. We then compare the two patient groups applying different filters.

RESULTS: This study indicates that patients in the UK exhibit a significantly higher adherence than patients in Germany. However, general adherence patterns are the same with men exhibiting a higher adherence than women and a positive correlation between adherence and age groups. In contrast the pattern between product strength and adherence is not shared between the two datasets. While the strongest product in the German market (320/9 mcg) shows the best adherence the weakest product (80/4.5 mcg) shows the worst adherence in the dataset for Germany. In contrast, the strongest product in the UK market (400/12 mcg) shows the worst adherence in the UK dataset while the medium strength (200/6 mcg) shows the best adherence.

CONCLUSIONS: Given that the correlation between product’s strength and adherence is the only striking difference between the two datasets working hypotheses can be drawn from this. For example, one hypothesis may be formulated where 200/6 mcg is the ‘sweet spot’ for this combination inhaler, with all strengths above or below this having an adverse effect on patient adherence.