Metabolic effects of controlled-release metoprolol in hypertensive men with impaired or diabetic glucose tolerance: a comparison with atenolol.

In a double-blind, randomized, cross-over study with a single-blind placebo run-in period a new controlled-release (CR) formulation of metoprolol 200 mg once daily was compared with atenolol tablets 100 mg once daily in 22 patients (age 60.9 +/- 0.93 (SE) years) with primary hypertension and impaired or diabetic glucose tolerance. Each period lasted for three weeks. The two agents produced similar blood pressure 3 h as well as 24 h after drug intake. Three hours after drug intake, heart rate was lower on atenolol than metoprolol CR treatment, indicating a higher degree of beta-receptor blockade for atenolol at this point in time, when the plasma concentration of atenolol was most likely to be close to its peak. Concentrations of blood glucose, serum insulin, and serum C-peptide in the fasting state or after an oral glucose load did not differ between the active agents. HbA1c was marginally, but significantly, lower on atenolol than metoprolol CR treatment. No differences were found in serum levels of total, low density lipoprotein (LDL), and high density lipoprotein (HDL) cholesterol or apoA-I, and apoB lipoproteins or triglycerides. In comparison to the placebo run-in period, both agents showed an unexpected improvement in glucose tolerance, a decrease in HDL cholesterol and for metoprolol CR a small, but significant decrease in LDL cholesterol. Thus, treatment with metoprolol CR tablets producing even plasma levels without high peak concentrations and conventional atenolol treatment had similar effects on metabolic control in hypertensive men and abnormal glucose tolerance.