Beta-blockers and diuretics. The HAPPHY and MAPHY studies

The question whether initial antihypertensive treatment with a beta-blocker prevents hypertensive complications better than initial treatment with a non-betablocker, mainly diuretic based treatment, has been studied in recent large-scale studies like the Medical Research Council (MRC) trial, the International Prospective Primary Prevention Study in Hypertension (IPPPSH), the Heart Attack Primary Prevention in Hypertension (HAPPHY) study and the Metoprolol Atherosclerosis Prevention in Hypertensives (MAPHY) study. The first three studies were unable to find a more beneficial effect of beta-blockers than of thiazide diuretics. The MAPHY study, however, found a lower total mortality, in the metoprolol treated group than in the diuretic treated. As the HAPPHY and MAPHY studies share a substantial part of patient-years and number of deaths, these diverging results have evoked confusion and debate. This paper presents the main results of both studies and discusses the possible reasons for the different outcome.