What are the obstacles to generic substitution? An assessment of the behaviour of prescribers, patients and pharmacies during the first year of generic substitution in Sweden.

Purpose: The aim of the present study was to investigate obstacles to generic substitution and savings achieved during the first year after Sweden introduced generic substitution in October 2002.

Methods: Normal prescriptions encompassed by generic substitution were included. Data on dispensed prescriptions in the Vastra Gotaland region was obtained from the National Corporation of Swedish Pharmacies. The outcome variables were investigated in three categories of drugs represented by two indicator drugs each.

Results: In total, 501,400 dispensed prescriptions of six indicator drugs were analysed. The prescriber opposed substitution in 1-8% of the dispensed prescriptions, varying between the indicator drugs. Patients declined substitution more frequently when the average saving per substitution was low. Substitution occurred most frequently in indicator drugs where the average saving per substitution was high. The total possible saving was 26 million Swedish krona (Swedish krona 1=U.S. $0.13) for the indicator drugs. The actual saving achieved by substitution was on average 60% of the total possible savings and was largely dependent on the extent to which the pharmacies kept the cheapest brand in stock.

Conclusions: Generic substitution has been implemented in practice although it did not reach full dividend during the first year. The potential savings from extended use of generic substitution are substantial.