Hemodynamic effects of once a day administration of combined chlorthalidone and metoprolol slow-release in essential hypertension

The effects of a fixed combination of chlorthalidone (25 mg) and metoprolol slow-release (200 mg) (CM) on 24 hour blood pressure (BP) and heart rate (HR) values and their variabilities were evaluated in 6 ambulant hypertensives by the Oxford method, to obtain continuous intra-arterial recording and by computer to have a beat-to-beat analysis of the data. Compared to pre-treatment values, average 24 hour HR and mean BP recorded after 7-10 days of once daily CM orally administration were reduced by 18.4 +/- 3.1 and 14.7 +/- 3.0%, respectively. The effects of CM were also evident during isometric and dynamic exercise, whose pressor and tachycardic responses were left unimpaired (BP) or were only slightly reduced (HR) by CM. The long- and short-term BP and HR variabilities (calculated as variation coefficients among and within half hours, and within minutes) were also left unaffected by CM. These findings indicate that once a day administration of CM effectively reduces BP and HR over the 24 hours, without interfering with cardiovascular homeostasis. The effective and persistent reduction in both these variables (as well as their occurrence during exercise) suggests that the antihypertensive action of this treatment is accompanied by a clear-cut reduction in cardiac work