Effects of felodipine on plasma digoxin levels and haemodynamics in patients with heart failure.

The interaction between felodipine and digoxin was studied after a single oral dose and at steady state in 14 patients with congestive heart failure. Felodipine (10 mg) was randomly given as an extended release (FER) tablet in a double-blind, placebo-controlled, cross-over fashion. In addition, felodipine (10 mg) was given openly as a plain tablet, following the double-blind period. Each period lasted for 7 d. Felodipine ER did not alter the pharmacokinetics of digoxin when given as a single dose or at steady state compared with placebo. At steady state the felodipine plain tablet resulted in an 11% increase (P less than 0.05) in peak plasma concentrations of digoxin. Systolic time intervals as noninvasively measured haemodynamic parameters were not significantly altered following the felodipine ER period, while the felodipine plain tablet significantly decreased the pre-ejection/left ventricular ejection time ratio compared to placebo.