Pharmacokinetic and pharmacodynamic properties of metoprolol in patients with impaired renal function

The pharmacokinetics of metoprolol have been studied in a group of patients with varying degrees of renal impairment and in healthy subjects after administration of 20 mg of metoprolol tartrate intravenously and 50 mg orally in a single dose and during steady-state conditions. There were no significant differences in the extent of bioavailability or rate of elimination of the drug between the 2 groups. The fraction of the oral dose systemically available during steady-state was 59 +/- 9% in the renal patients and 55 +/- 7% in the control group. Total body clearance in the patients with renal failure was 1.0 +/- 0.1 L/min and in the healthy subjects it was 0.8 +/- 0.1 L/min. The corresponding values for the elimination half-life were 4.6 +/- 1.2h and 4.1 +/- 1.0h, respectively. The beta-adrenoceptor blocking effect of metoprolol (determined as percent reduction of exercise heart rate) did not differ significantly between the 2 groups during steady-state conditions. The effect on exercise heart rate was linearly related to the log of the plasma concentration of metoprolol. The relationship was identical for the single dose and during steady-state conditions, indicating that accumulation of metabolites in patients with renal failure does not influence the beta-blocking properties of metoprolol.