Impact of a cost sharing drug insurance plan on drug utilization among individuals receiving social assistance.

Background: A cost-sharing drug insurance plan has been implemented among people receiving social assistance who had previously free access to medications.

Objective: To assess the impact of this drug plan on the use of three classes of medications: inhaled corticosteroids, neuroleptics and anticonvulsants.

Methods: From the computerized drug databases of the Régie de l'assurance maladie du Québec (RAMQ), we selected three random samples of Quebec residents receiving social assistance between August 1992 and June 1997 and aged 64 years or less: 55890 users of inhaled corticosteroids, 29461 users of neuroleptics and 44916 users of anticonvulsants. We also obtained data for individuals privately insured by the Commission de la construction du Québec (control group). Comparison of the monthly consumption of medications before and after the new drug plan was done using time series models.

Results: For individuals receiving social assistance and using inhaled corticosteroids, we observed a statistically significant decrease of 37% of the monthly consumption for the 11 months following the new drug plan. For neuroleptics and anticonvulsants, we observed a non significant decrease of 9 and 10%, respectively. No decrease in drug consumption was observed in the control group.

Conclusion: Inhaled corticosteroids was the only class of medications that was found to decrease significantly after the implementation of the drug insurance plan.