Objectives: To compare the hemodynamic effects of twice daily metoprolol tartrate (MT) and once daily metoprolol succinate (MS) in congestive heart failure patients.
Background: Adverse hemodynamic effects with MT demonstrated during initiation persist with drug readministration during chronic therapy.
Methods: Patients were randomly assigned to 6.25 mg MT or 25 mg MS orally and the dose was gradually increased to a target of 50 mg twice a day or 100 mg once a day, respectively. Hemodynamic measurements were obtained at baseline and after three months of therapy--both before and after drug readministration.
Results: Long term metoprolol therapy produced significant functional, exercise and hemodynamic benefits with no difference in response between either metoprolol preparation in the 27 patients (MT [14], MS [13]). When full dose metoprolol was readministered during chronic therapy, there were parallel adverse hemodynamic effects in both drug groups. Cardiac index decreased by 0.6 liters/min/m2 (p < 0.0001) with MT and by 0.5 liters/min/m2 (p < 0.0001) with MS. Systematic vascular resistance increased by 253 dyne-sec-cm(-5) (p < 0.001) with MT and by 267 dyne-sec-cm(-5) (p < 0.0005) with MS. Stroke volume index decreased by 7.0 ml/m2 (p < 0.0005) with MT and by 6.5 ml/m2 (p < 0.0001) with MS, while SWI decreased by 6.2 g-m/m2 (p < 0.0005) with MT and by 6.0 g-m/m2 (p < 0.001) with MS.
Conclusion: Metoprolol tartrate and MS produce similar hemodynamic and clinical effects acutely and chronically despite the fourfold greater starting dose of MS used in this study. A more rapid initiation with readily available starting doses of MS may offer distinct advantages compared with MT in treating chronic heart failure patients with beta-adrenergic blocking agents.