About magnesium sulphatesaline laxative, osmotically actingmechanism of action of magnesium sulphateoral: magnesium sulfate increases peristaltic activity by causing osmotic retention of fluids, thus resulting in bowel evacuation. parenteral: magnesium sulfate decreases levels of acetylcholine in motor nerve terminals. it also acts on the myocardium by decreasing the rate of sa node impulse formation and prolonging the conduction timeindications for magnesium sulphate1.seizures in pregnancy 2.hypomagnesaemia 3.heart attack 4.asthma 5.constipation