Compositions are provided that are useful for the preparation of a medicament. The compositions comprise granules having a layer of sodium picosulphate coated on potassium bicarbonate. Additional granules having a layer of magnesium oxide coated on a core of citric acid are also provided. The two types of granules may be combined to obtain mixtures (preferably homogeneous or substantially homogeneous mixtures) of the two types of granules, which are useful, e.g., as pharmaceutical compositions.