Comparing the cumulative incidences of add-on therapy among the major antihypertensive classes in 2531 Asian patients: a cohort study

BACKGROUND: Published literature addressing the efficacy of different antihypertensive drug classes among Asian patients is scarce. METHODS: This cohort study included all patients prescribed their first-ever antihypertensive monotherapy without concomitant use of chronic medications in two primary care clinics in Hong Kong during 1990-2002. The incidence of add-on therapy within 48 weeks because of suboptimal blood pressure control was evaluated and compared among different age and gender groups. RESULTS AND DISCUSSION: Among the 2531 patients, the incidence of add-on therapy among users of angiotensin converting enzyme inhibitors (ACEI) was highest in young females (31.1%, 95% CI 22.2%, 40.0%, P < 0.001) and elderly females (18.0%, 95% CI 11.3%, 24.7%, P = 0.049) as compared with thiazide diuretics, beta-blockers and calcium channel blockers. The incidence of add-on therapy among young males (20.3%, 95% CI 11.1%, 29.5%; P > 0.50) and elderly males (12.5%, 95% CI 3.8%, 21.2%) was also highest with the ACEI than other drug classes although statistical significance was not reached. CONCLUSION: The incidence of add-on therapy among first-time antihypertensives appear to be significantly different between drug classes. This deserves further investigation.