Les Medicaments et la Sante Publique

摘要

Background: The impact of the type of drug plan on adherence to and cost of antihypertensive medications within the context of a universal drug insurance program is not known.Objective: To compare patient’s adherence to and cost of antihypertensive medications between adult patients with public and private drug insurance in the province of Quebec, Canada.Methods: A matched retrospective cohort was reconstructed from the linkage of the Régie de l’assurance maladie du Québec (RAMQ) and reMed databases between March 2008 and May 2010. The cohort included 186 privately and 1,747 publicly-insured patients aged 18-64 years who were treated with one or two antihypertensive medications. Adherence was measured with the proportion of days covered (PDC) over one year. Cost of antihypertensive medications included the cost of the medication, the mark-up and the dispensing fees. Linear regression models were used to estimate the adjusted mean difference of the PDC and the monthly cost per patient for antihypertensive therapy between the two groups. In addition, the cost for 30-day prescriptions for the entire class, sub-classes and eachantihypertensive medication was compared between patients with private and public insurance with T-tests.Results: More than 70% of patients were 50-64 years, 90% were prevalent users of antihypertensive medications, and 90% of the publicly and 72% of the privately insured patients had only one antihypertensive medication at cohort entry. The mean PDC was 90.3% for privately and 94.0% for publicly-insured patients with one antihypertensive medication at cohort entry. Corresponding figures were 92.9% and 80.7% for patients with two antihypertensive medications. For new users, the mean PDC was 58.8% for privately and 65.0% for publicly-insured patients with one antihypertensive medication atcohort entry. The average monthly cost per patient for antihypertensive medications was $41.52 in the private and $32.21 in the public group. Using 30-day prescriptions only, the average cost for the entire class, each sub-class and for individual antihypertensive medications was higher for privately-insured than publicly-insured patients except for labetalol (beta blocker) and triamterene (diuretic).Conclusion: The cost of antihypertensive medications was 29% higher for patients with private drug insurance, although adherence was high among prevalent users and similar between the two groups. Regulation of dispensing fees on the public side and the high percentage of prevalent users in both groups may explain the results.