Plasma levels and effect on heart rate and blood pressure of metoprolol after acute oral administration in 12 geriatric patients.

Metoprolol, a cardioselective beta-blocking agent, has been given orally to 12 geriatric patients with moderate hypertension. Drug levels of metoprolol as well as the effect of the drug on resting heart rate and BP were studied. Metoprolol was given in a dose of 20 mg, and 8 of the 12 patients also received a 50 mg dose. After the 20 mg dose the peak drug plasma concentration varied between 5 and 80 ng/ml (mean 33), and after the 50 mg dose between 14 and 212 ng/ml (mean 111). This variation is much greater than that seen in earlier studies on healthy volunteers and on a group of non-geriatric hypertensive patients. Plasma half-life of metoprolol averaged about 3.5 hours after both the 20 mg and the 50 mg dose; this does not differe from the plasma half-life in earlier studies in younger age groups. The variability observed in the study might be explained multifactorially, e.g. by different body weight, absorption and/or first-pass effect of the drug.