Commentary on the Carvedilol or Metoprolol European Trial (COMET)

β-Adrenergic blockade is commonly and successfully used to treat chronic heart failure. Until recently, few data were available on which to base selection of a particular β-blocking agent. The Carvedilol or Metoprolol European Trial (COMET) provides evidence that β-blockers are not interchangeable. The trial compared carvedilol, a nonselective β-blocker with α-adrenergic blocking and numerous ancillary activities, with metoprolol tartrate. In comparison to metoprolol tartrate, significant reductions in all-cause mortality and cardiovascular mortality were observed with carvedilol. These data indicate that cardiovascular benefit may be obtained from switching patients from metoprolol tartrate to carvedilol.