מתוך medicontext.co.il
WESTPORT, CT (Reuters Health) – In patients with chronic heart failure who have responded well to beta-adrenergic blockade with either metoprolol or carvedilol, switching from one drug to the other offers little additional benefit, study results show.
"It has recently been suggested that carvedilol has more pronounced effects on left ventricular ejection fraction (LVEF) compared with metoprolol," Dr. Christoph Maack, of Universitהts-kliniken des Saarlandes in Hamburg, and colleagues note in the October issue of the Journal of the American College of Cardiology. However, in patients well maintained on metoprolol the safety and clinical value of switching to carvedilol had been uncertain.
To investigate, the German cardiologists prospectively studied 44 patients with heart failure who had responded well to more than 1 year of treatment with metoprolol or carvedilol. The patients were switched to an equal dose of the other beta-blocker.
Six months after crossover, "further improvement of ventricular function occurred irrespective of the beta-blocker used," the team reports. The two agents improved LVEF to a similar extent. Moreover, there were no significant changes in either New York Heart Association functional class or any hemodynamic parameters at rest.
Dobutamine stress echocardiography indicated that both agents produced a comparable increase in cardiac output in response to beta-adrenergic stimulation, albeit by different mechanisms. "In metoprolol-treated patients…cardiac output was maintained by a substantial rise in heart rate," the investigators report. In carvedilol-treated patients, "an increase of stroke volume appeared to be the relevant mechanism."
Dr. Maack's team also notes that acute hypotension or bradycardia developed at first dose in five patients (21%) switched from carvedilol to metoprolol. This did not happen in any patient crossing over from metoprolol to carvedilol. They suggest that when switching from carvedilol to metoprolol, the initial metoprolol dose "should not exceed 50 mg per 25 mg of carvedilol, with consecutive up-titration to the maximum tolerated dose."
When a patient crosses over from metoprolol to carvedilol, they recommend initial use of 25 mg of carvedilol per 100 mg of metoprolol, with similar up-titration to the maximum tolerated dose.
The researchers say that definitive data on the comparative effects of carvedilol and metoprolol on mortality will have to await completion of the Carvedilol Or Metoprolol European Trial (COMET).
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