Mechanism of actionaluminum hydroxide: neutralizes stomach hydrocloride to form alcl3 salt plus water- increases gastric phmagnesium hydroxide: promotes bowel evacuation by causing osmotic retention of fluid, which causes the colon to distend with increased peristaltic activity- forms magnesium chloride when reacts with hydrochloric acidsimethicone: disperses and prevents gas pockets in the gi system by decreasing surface tension of gas bublescontraindicationshypersensitivity to any component of the formulationcautionscaution in renal failure