Impact of Drug Plans on Adherence to and the Cost of Antihypertensive Medications Among Patients Covered by a Universal Drug Insurance Program

Background: This study aimed to assess the impact of the type of drug plan on adherence to antihypertensive medication treatment as well as the cost of these medications within universal drug insurance programs. Methods: To compare adherence to antihypertensive medication treatment and the cost of antihypertensive medications between adults with public and private drug insurance in the province of Quebec, Canada, we reconstructed a matched retrospective cohort by linking data recorded in 3 administrative databases between March 2008 and May 2010. The cohort included 186 privately and 1747 publicly insured patients aged 18-64 years who were treated with 1 or 2 antihypertensive medications. Adherence measured with the proportion of days covered (PDC) over 1 year and the cost of antihypertensive medications were evaluated for new and prevalent users separately. Results: More than 70% of patients were 50-64 years old and 90% of the publicly and 72% of the privately insured patients were using only 1 antihypertensive medication. The mean PDC among new users of 1 antihypertensive medication was 58.8% for privately insured patients and 65.0% for publicly insured patients, but the difference was not statistically significant. However, privately insured patients treated with 2 antihypertensive medications were more likely to be adherent (PDC-P, 15.0%; 95% confidence interval, 7.0-24.0). Privately insured patients (CAD$41.52) had to pay significantly more for their antihypertensive medications than did publicly insured patients (CAD$32.21). Conclusions: The cost of antihypertensive medications was higher for patients with private drug insurance, although adherence was similar in both groups. The results may reflect regulation of dispensing fees for publicly insured patients.