Effect of Phosphate or Magnesium Cathartics on Serum Calcium

Abstract
The administration of a commercial phosphate cathartic in conventional doses to normal subjects prior to barium enema resulted in a striking increase in serum phosphorus levels followed by a decline in serum calcium levels in all subjects. Changes were highly significant (P <.01) when compared with control subjects who were prepared for the same procedure with magnesium citrate. Levels of serum potassium also decreased significantly (P <.01) but not serum sodium, chloride, bicarbonate, or magnesium. (Arch Intern Med 138:1114-1116, 1978)