Constipation, nausea, vomiting are the common side effects. Large doses can cause intestinal obstruction. Excessive doses or even normal doses in patients with low phosphate diets, may lead to phosphate depletion accompanied by increased resorption and urinary excretion of calcium with risk of renal rickets in the young or osteomalacia in older patients.
Magnesium trisilicate may cause diarrhoea, mucosal irritation and absorption of magnesium may occur if there is gastro-intestinal atony or obstruction.
After excessive use and especially in excessive use, hypermagnesemia may result. The symptoms are flushing of the skin, thirst, hypotension due to vasodilatation, drowsiness, loss of tendon reflexes due to neuromuscular blockade, weakness, respiratory depression, cardiac arrhythmias, coma and cardiac arrest.