BACKGROUND: The objective of this study was to test the assumption that liberalizing community pharmacy ownership in Iceland would lead to increased irrational use of over-the-counter pain relievers containing codeine.

METHODS: Based on this assumption we built and tested a model using an interrupted time series design that contrasts the monthly sales data for over-the-counter pain relievers containing codeine before and after the legislation took effect.

RESULTS: The total use of over-the-counter pain relievers containing codeine as well as those containing paracetamol and codeine has risen steadily throughout the period under study. The interrupted time series did not show a substantial effect from the legislative change on the use of all over-the-counter codeine pain relievers, paracetemol with codeine, and aspirin with codeine combinations.

CONCLUSION: The assumption that increased access leads to irrational use of over-the-counter medicines is not substantiated in the case of over-the-counter pain relievers containing codeine.