Effect of particle size on the bioavailability of digoxin

The bioavailability of digoxin in three tablets prepared from materials with different particle sizes was measured in healthy volunteers in a cross-over study using an alcoholic solution of digoxin as a reference standard. Its bioavailability in tablets with particle sizes of 7 mu or 13 mu was 78-97% of that of digoxin in solution. The tablet with largest particle size (102 mu) showed markedly lower bioavailability than the reference solution, namely 39%. It is obvious that particle size is an important determinant of the dissolution rate and bioavailability of digoxin.