Combinations of laxatives for bowel preparation: are they necessary?

To determine whether combinations of saline and surface-acting laxatives have any superior action over saline laxatives alone in cleansing the colon, patients having double-contrast barium enema examinations were randomly allocated to magnesium citrate alone and magnesium citrate with either oral or rectal bisacodyl. The addition of bisacodyl conferred no benefit over magnesium citrate alone. A companion study of magnesium citrate and sodium picosulphate (Picolax) showed no benefit over magnesium citrate alone. It is concluded that it is unnecessary to add a contact or surface-acting laxative to 25 g of magnesium citrate for bowel preparation.