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Abstract
Furthermore, [Philip Poole-Wilson] and colleagues state that the mean dose of metoprolol CR/XL used in MERIT-HF of 159 mg once daily corresponds to 106 mg of short-acting metoprolol tartrate. Data published by Andersson and colleagues2 indicate this assumption is wrong; in their study, 200 mg and 100 mg of metoprolol CR/XL were compared with short-acting metoprolol 50 mg three times daily in patients with heart failure. Mean heart rate over 24 h was 63[middot]56 bpm on 200 mg metoprolol CR/XL, 67[middot]94 on 100 mg metoprolol CR/XL, and 67[middot]16 bpm on 50 mg short-acting metoprolol three times daily. Andersson and colleagues did not study short-acting metoprolol 50 mg twice daily, but we believe the corresponding heart rate over 24 h would have been about 2 bpm higher than in was for 50 mg three times daily. These data2 indicate that 100 mg metoprolol CR/XL corresponds to 150 mg of short-acting metoprolol. Hence, the target dose used in COMET of 50 mg short-acting metoprolol twice daily is less than the target dose of 200 mg metoprolol CR/XL used in MERIT-HF.