Effects of ranitidine on the disposition of metoprolol

The effects of ranitidine on the pharmacokinetics of metoprolol were examined in two studies. In the first study, pharmacokinetics of single doses of metoprolol were examined in six subjects before, during and after ranitidine administration for 1 week. Peak concentrations of metoprolol were increased on ranitidine but its half-life and clearance were unaltered. In the second study, 12 subjects received metoprolol twice daily for 1 week; once with ranitidine and once with placebo. Ranitidine had no effects on the chronic-dose pharmacokinetics or pharmacodynamics of metoprolol. The chronic dose study suggests no inhibition of the metabolism of metoprolol by ranitidine. The single dose study suggests, however, that some interaction of an as yet unknown nature, cannot be excluded.