Bioavailability and related heart function index of digoxin capsules and tablets in cardiac patients

A loading dose of digoxin (750 microgram) in two commercial formulations was administered to 14 patients with heart disease according to a crossover design. One formulation consisted of soft gelatin capsules containing a solution of digoxin; the other formulation was compressed tablets. All parameters investigated, i.e., serum peak height, time of the peak, area under the serum level--time curve (AUC), and area above the Q--S2I (electromechanical systole) decrease (obtained from polycardiographic evaluation), showed better bioavailability of digoxin capsules than tablets, averaging 36.3%. The better bioavailability of digoxin capsules than tablets seems to be more evident in heart disease patients than that encountered previously in healthy subjects. The AUC and the area above the Q-S2I decrease were linearly correlated only with digoxin capsules.