[SwapINN: analytic study about prescription swaps at pharmacies]

In order to cut spending, compulsory INN prescription was suggested in Portugal during 2012. This instigated discussion among stakeholders in the matter. The authors studied prescription-dispensing dynamics in a real population.

To determine the percentage of swapped prescriptions; to assess factors associated with the swap; to analyse justifications for doing so; to quantify the cost difference for patients and the National Health Service.

Analytic study. Convenience sample consisting of all prescriptions from a Primary Health Care unit, from the 19th to the 23rd December 2011. Third day follow-up, using phone call interviews. Software: Excel and SPSS.

Chi-square and Mann-Whitney, SL = 0.05.

Total of 255 prescriptions. Majority prescribed to women (62%), mean age of 52, four years of school education and for acute situations. A percentage of 31% of prescribed drugs were swapped. The swaps had no statistical relation with age, sex or literacy of the patient, nor with the prescriber or pharmacy. Swapping of prescribed drugs for chronic situations was lower (p < 0.001), as well as for original brand prescriptions (p < 0.001). Anti-infectious and anti-allergic were the most swapped groups (p = 0.009). Seventy-two percent of users were not aware of the swap. Regarding the swapped drugs, users paid on average 79% more than what was originally prescribed, and the National Health Service 5% more.

The authors found changes in 31% of the prescriptions, with higher costs for both users and National Health Service. Selection, information and registration bias were considered. With compulsory INN prescriptions, we suggest regular analysis of prescription-dispensing dynamics, based on the available national data.