Effect of Metoprolol Succinate in Patients with Stable Angina and Elevated Heart Rate Receiving Low-Dose β-Blocker Therapy

Aims: β-blockers are underused in Chinese patients with coronary heart disease. The prescribed dose is often low. The aim of this study was to investigate the effect of metoprolol succinate doses of 95 mg and 190 mg on heart rate (HR) control, as well as drug tolerance, in Chinese patients with stable angina, low-dose β-blocker use and unsatisfactory HR control. Methods: This was a multicenter, randomized, open-label, parallel-group trial in 15 clinical sites. Patients with stable angina, taking low-dose β-blockers (equivalent to metoprolol succinate 23.75-47.5 mg/day), and having a resting HR of ≥ 65 bpm were enrolled and randomized to either the metoprolol 95-mg group or the 190-mg group. The change in 24-h average HR from baseline recorded by Holter monitoring and the percentages of patients with resting HR controlled to ≤ 60 bpm were compared between the two groups. Results: Two hundred thirty-one patients entered the intent-to-treat population for the main analysis. The change in 24-h average HR from baseline was -0.62 ± 0.66 bpm in the 95 mg group and -2.99 ± 0.62 bpm in the 190 mg group (p = 0.0077) after 8 weeks of treatment. The percentages of patients with resting HR controlled to ≤ 60 bpm were 24.1% (95% CI: 16.35%, 31.93%) and 40.0% (95% CI: 31.05%, 48.95%), respectively (p = 0.0019). Only 4 and 2 of the patients, respectively, discontinued the study drugs because of hypotension or bradycardia. Conclusions: The metoprolol succinate dose of 190 mg is superior to the 95 mg dose in terms of HR control, in Chinese patients with stable angina, low-dose β-blocker use and unsatisfactory HR control. Both doses were well tolerated.