Comparative pharmacokinetics and pharmacodynamics of cardiac glycosides.

1 The pharmacokinetics and pharmacodynamics of ouabain, digoxinn and beta-methyl digoxin (medigoxin) have been investigated in a crossover study in four normal healthy volunteers. 2 Pharmacokinetics were studied using [3H]-labelled glycosides and the shortening of the left ventricular ejection time (LVET) was used as a measure of the effect of the drugs. A graded exercise protocol was used to correct for the effects of heart rate on LVET. 3 In three of the four subjects, both digoxin and beta-methyl digoxin produced a shortening in the LVET, but no such change could be detected with ouabain in any of the four subjects. 4 There was a good linear correlation between the shortening of the LVET and the amounts of digoxin or beta-methyl digoxin present in the body tissues. 5 One subject who showed no drug-related LVET shortening had greatly enhanced clearances of all three drugs studied.