Our study shows that over half of the repeat prescriptions for inhaled corticosteroids dispensed to patients over 60 years showed an undersupply. Therefore, it is likely that elderly patients on long-term therapy have a non-optimal drug use of their preventive asthma/COPD medication.

Refill adherence determined from manually collected repeat prescriptions and from a pharmacy record database did not differ for a 1-year period. Four-year data might give a better overview of patients' refill adherence than 1-year data.

The majority of the patients, and particularly those in the youngest age group used asthma/COPD drugs only sporadically. This may indicate undermedication which is likely to have a negative impact on patient outcome.

Patients showed higher refill adherence for their diabetes drugs than their asthma/COPD drugs. Our hypothesis that patients with satisfactory refill adherence to antihyperglycaemic drugs would also have satisfactory refill adherence to asthma/COPD drugs, was not supported.

Both undersupply and oversupply of prescribed medicines are common in Sweden. Patients with a refill adherence below 80% seem to have less than half of the prescribed treatment available. Oversupply or drug stockpiling occurs more frequently among exempt than among non-exempt patients, and this oversupply leads to high unnecessary costs.