Abstract 14017: Initial Antihypertensive Prescription and Switching: A 5-Year Cohort Study from 250,851 Patients

Abstract

Purpose: Adverse effects of antihypertensive therapy incur substantial cost. We evaluated whether any major classes of antihypertensive drugs were significantly associated with switching as a proxy measure of medication side effects.

Methods: From a clinical database, all adult patients newly prescribed an antihypertensive mono-therapy in Hong Kong between the years 2001-2003 and 2005 were included. Those who paid only one visit, died or stayed in the cohort for < 180 days after the prescription, or prescribed more than one antihypertensive agent were excluded. The factors associated with switching at 180 days were evaluated by multivariate regression analyses. Age, gender, payment status, service type, district of residence, drug class, systolic and diastolic blood pressure levels were predictor variables.

Results: From 250,851 subjects, 159,813 patients were eligible. A total of 6,163 (3.9%) switched their medications within 180 days. Patients prescribed thiazide diuretics had the highest switching rate (5.6%), followed by ACEIs (4.5%), CCBs (4.4%) and β-blockers (3.2%). When compared with ACEIs, patients on thiazide diuretics were significantly more likely to be switchers (adjusted odds ratio [AOR]: 1.49, 95% C.I. 1.31-1.69, p<0.001), whilst patients prescribed CCBs and β-blockers were similarly likely to have switching. Following these patients up for 5 years showed that thaizide had the most marked increase in switching rate.

Conclusion: The higher rates of switching among thiazide diuretics in this study might represent a concern on their adverse event rates or efficacy profiles in this Chinese population. Patients prescribed thiazide diuretics for longer term should be observed for their intolerability.