Background: In Australia, many patients who are initiated on asthma controller inhalers receive combination inhaled corticosteroid/long-acting beta2-agonist (ICS/LABA) despite having asthma of sufficiently low severity that ICS-alone would be equally effective and less costly for the government.
Methods: We conducted a discrete choice experiment (DCE) in a nationally representative sample of adults (n = 792) and parents of children (n = 609) with asthma. Mixed multinomial models were estimated and calibrated to reflect the estimated market shares of ICS-alone, ICS/LABA and no controller. We then simulated the impact of varying patient co-payment on demand and the financial impact on government pharmaceutical expenditure.
Results: Preference for inhaler decreased with increasing costs to the patient or government, increasing chance of a repeat visit to the doctor, and if fewer symptoms were present. Adults preferred high-strength controllers, but parents preferred low-strength inhalers for children (general beneficiaries only). The DCE predicted a higher proportion choosing controller treatment (89%) compared to current levels (57%) at the current co-payment level, with proportionately higher uptake of ICS-alone and a lower average cost per patient [32.73 Australian dollars (AU$) c.f. AU$38.54]. Reducing the co-payment on ICS-alone by 50% would increase its market share to 50%, whilst completely removing the co-payment would only have a small marginal impact on market share, but increased average cost of treatment to the government to AU$41.04 per person.
Conclusions: Patient-directed financial incentives are unlikely to encourage much switching of medicines, and current levels of under-treatment are not explained by patient preferences. Interventions directed at prescribers are more likely to promote better use of asthma medicines.