Influence of soft gelatin on digoxin absorption.

1 The influence of encapsulation in soft gelatin on the absorption of digoxin from a solvent mixture of polyethylene glycol 400 90% W/W, ethanol 6% W/W, propylene glycol 3% W/W and water 1% W/W was studied in eight healthy volunteers. 2 Each volunteer received 0.6 mg digoxin as solution alone, as three intact capsules containing digoxin solution, as three capsules containing digoxin solution sectioned in half and as three capsules containing digoxin solution dissolved in water prior to administration. 3 There was no significant difference between the four treatments in terms of area under the plasma concentration--time curves for 7 h, peak plasma concentrations, time to peak or in the cumulative urinary excretion for 6 days. 4 It is suggested that a constituent of the solvent rather than the presence of or encapsulation within soft gelatin may be the determining factor in enhanced absorption of digoxin from soft gelatin capsules as compared to aqueous solution or tablets of rapid dissolution rate.