ORIGINAL ARTICLE Persistence and discontinuation patterns of antihypertensive therapy among newly treated patients: a population-based study C Bourgault 1,2 , M Se ´ne ´cal 1 , M Brisson 1 , MA Marentette 1 and J-P Gre ´goire 3 1 Merck Frosst Canada Ltd, Kirkland, QC, Canada; 2 Department of Medicine, McGill University, Montre´al,QC, Canada; 3 Population Health Research Unit and Faculty ofPharmacy, Laval University, Que´bec, QC, Canada The objective was to assess persistence with anti- hypertensive therapy (AHT) and discontinuation patterns in patients newly dispensed different antihypertensive drug classes in a natural Canadian population-based setting. Hypertensive patients initiating AHT monother- apy were included in this 3-year retrospective cohort study (N ¼ 21 326) using the Saskatchewan health-care databases. Persistence was defined as consistently refilling a new prescription for AHT within 90 days of a previous dispensing. New courses of AHT were also documented in nonpersistent patients. Kaplan–Meier and Cox regression analyses were used to compare persistence and new courses of therapy across initial drugs. Compared to the newer angiotensin II antago- nists (AIIAs), the likelihood of discontinuing therapy over the 39-month study period was significantly higher for angiotensin-converting enzymes inhibitors (HR ¼ 1.29; 95% CI ¼ 1.16–1.43), calcium channel blockers (HR ¼ 1.42; 95% CI ¼ 1.27–1.60), beta blockers (HR ¼ 1.62; 95% CI ¼ 1.45–1.80) and diuretics (HR ¼ 1.92; 95% CI ¼ 1.73– 2.14). In the year following treatment discontinuation, between 54 and 75% of patients initiated a second course of treatment. Patients initiated on an AIIA had a significantly higher likelihood of starting a new course of therapy after a first treatment discontinuation, compared to all other agents. In conclusion, hyperten- sive patients initiated on an AIIA not only had greater persistence to AHT but were also more likely to initiate a new course of AHT after discontinuation than those initiating treatment with other agents. Further studies are required that relate intermittent treatment beha- viours to health outcomes and costs in hypertension. Journal of Human Hypertension (2005) 19, 607–613. doi:10.1038/sj.jhh.1001873; published online 26 May 2005 Keywords: antihypertensive drugs; angiotensin receptor blockers; persistence Introduction Hypertension, defined as systolic blood pressure higher than 140 mmHg and/or diastolic pressure higher than 90 mmHg, is a key factor in the onset of cardiovascular disease (CVD), the leading cause of death in North America. 1,2 Hypertension is a major health problem affecting more than 20% of the Canadian population. 3 The 1999 total cost of treating hypertension in the US was estimated to be $33.3 billion: 4 direct costs of medical care included $8.1 billion for drugs, $7.1 billion for hospital and nursing home care, $1.5 billion for home health care and other medical requirements, and $8.8 billion for lost productivity resulting from hyperten- sion-related morbidity and mortality. 4 The 2004 Canadian recommendations for the management of hypertension, 5 the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, 2 and the International Society of Hypertension Guidelines for the Management of Hypertension 6 are examples of attempts to address the need for continued improve- ment in the management of hypertension. However, there is ample evidence for poor control of hyper- tension in many populations. For instance, it has been estimated that in Canada, only 16% of hypertensive patients are controlled, 23% are treated but not controlled, 19% are not treated and 42% are unaware of their condition. 7 In the US, it has been estimated that only 34% of hypertensive patients are controlled, 41% are not treated and 30% are unaware of their condition. 2 A lack of adherence to antihypertensive (AHT) therapy is considered to contribute to the inappropriate control of hyper- tension for the majority of hypertensive patients. 2 The association of lack of blood pressure control to cardiovascular risk and premature death has been widely documented. The usefulness of treating high Received 10 December 2004; revised 1 March 2005; accepted 2 March 2005; published online 26 May 2005 Correspondence: Dr C Bourgault, Merck Frosst Canada Ltd, Health Economics and Outcomes Research, 16 711 TransCanada Highway, Kirkland, QC, Canada H9H 3L1. E-mail: chantal_bourgault@merck.com Journal of Human Hypertension (2005) 19, 607–613 & 2005 Nature Publishing Group All rights reserved 0950-9240/05 $30.00 www.nature.com/jhh