Is the level of patient co-payment for medicines associated with refill adherence in Sweden?

Background: In the Swedish reimbursement scheme, the co-payment is based on the price of the product and decreases in a stepwise manner as the total accumulated co-payment increases. The aim of this study was to analyse how refill adherence in Sweden varies according to patient's co-payment level for medicines, with antiepileptic drug (AED) use as an example. Methods: Prevalent AED users aged 18-85 years who purchased an AED between 1 January and 30 June 2007 were identified in the Swedish Prescribed Drug Register and followed for a maximum of 2 years. Patient time was categorized based on patient's accumulated co-payment for all drugs per reimbursement period. The continuous measure of medication acquisition (CMA) was used to estimate refill adherence in relation to the patients' co-payment level. Associations between patients' co-payment for all medicines and refill adherence were assessed with multilevel mixed-effects linear regression, accounting for clustering within patients. Results: The study population included 2210 patients (mean age: 56 years; 54% men). CMA for AED was 91% for patients where the co-payment corresponded to 100% of the price. Compared with these patients, refill adherence for AED was 2-4% higher (P < 0.001) for patients with reduced co-payment (co-payment of 50% of the price). Higher age, higher income and fenytoin use were also associated with a higher refill adherence for AED. Conclusions: Using AED as an example, a higher level of reimbursement was associated with a higher refill adherence compared with full co-payment in Sweden.