Symptoms of overdose include gastrointestinal irritation and watery diarrhoea. Magnesium poisoning may produce hypermagnesaemia, symptoms of which include nausea, vomiting, flushing, thirst, hypotension, drowsiness, confusion, loss of tendon reflexes, muscle weakness, respiratory depression, cardiac arrhythmias, coma and cardiac arrest.
Treatment
Treatment consists of the intravenous administration of calcium gluconate injection 10% in a dose of 10-20ml to counteract respiratory depression or heart block. If renal function is normal, adequate fluids should be given to assist removal of magnesium from the body. Dialysis may be necessary in patients with renal impairment or severe hypermagnesaemia.
Hypersensitivity to any of the ingredients.
None.
Diarrhoea may occur which is dose related.
In patients with impaired renal function there may be sufficient accumulation of magnesium to produce toxic effects.
Magnesium hydroxide has been used for many years and no further data are presented in this section.
Milk of Magnesia is indicated as an antacid for the symptomatic relief of stomach discomfort, indigestion, hyperacidity, heartburn and flatulence; and as a laxative for constipation.
Magnesium hydroxide is practically insoluble in water and solution is not effected until the hydroxide reacts with hydrochloric acid in the stomach to form magnesium chloride. Its neutralising action is almost equal to that of sodium bicarbonate. When the dose is in excess of that required to neutralise the acid the intragastric pH may reach pH 8 or 9. Acid rebound following magnesium hydroxide is clinically insignificant.
Magnesium hydroxide has an indirect cathartic effect resulting from water retention in the intestinal lumen.
Magnesium hydroxide exerts its antacid therapeutic effect rapidly within the gastro-intestinal tract following oral administration and this action is therefore independent of pharmacokinetic properties. Following oral administration, about one third to half the magnesium is absorbed very slowly from the small intestine. Magnesium salts are excreted mainly in the urine with small amounts in the faeces and saliva.
Adequate fluid intake should be maintained during use. If diarrhoea occurs especially in children or the elderly, discontinue use immediately. In case of renal impairment a doctor should be consulted as hypermagnesaemia may occur. If symptoms persist or worsen, a doctor or pharmacist should be consulted.
Do not use as a laxative for more than three consecutive days, or as an antacid for more than fourteen consecutive days.
If a laxative dose is needed every day or if there is a persistent abdominal pain further medical advice should be sought.
Users taking medicines either physician prescribed or self-prescribed should consult a doctor or pharmacist before use.
Keep out of the reach and sight of children.
Magnesium hydroxide is unlikely to cause any effects on the ability to drive and use machines.
Use a 5 ml spoon or the dosing cup provided.
Doses may be taken with milk or water if desired.
Do not exceed the stated dose.
As an antacid:
| Adults: | 5-10 ml (one or two 5 ml spoonfuls or fill the dosing cup to the first or second line). Repeat as necessary to a maximum of 60 ml in 24 hours. |
| Children aged 3-12 years: | 5 ml (one spoonful or first line in dosing cup). Repeat as necessary to a maximum of 30 ml in 24 hours. |
As a laxative:
| Adults: | 30-45 ml at bedtime. Repeat nightly, reducing dose each night until constipation is relieved. |
| Children aged over 3 years: | 5-10 ml at bedtime. |
| Children aged under 3 years: | to be given only on the advice of a doctor. |
| Elderly: | As adult dose. |
Shake bottle well before use. Use within 6 months of opening.
