Magnesium Oxide in Constipation

Abstract

Magnesium oxide has been widely used as a laxative for many years in East Asia, yet its prescription has largely been based on empirical knowledge. In recent years, several new laxatives have been developed, which has led to a resurgence in interest and increased scientific evidence surrounding the use of magnesium oxide, which is convenient to administer, of low cost, and safe. Despite these advantages, emerging clinical evidence indicates that the use of magnesium oxide should take account of the most appropriate dose, the serum concentration, drug-drug interactions, and the potential for side effects, especially in the elderly and in patients with renal impairment. The aim of this review is to evaluate the evidence base for the clinical use of magnesium oxide for treating constipation and provide a pragmatic guide to its advantages and disadvantages.

Keywords: constipation; hypermagnesemia; laxative; magnesium oxide.

Figure 1

The pharmacokinetics of magnesium oxide. Magnesium oxide (MgO) is converted to sodium hydrogen carbonate (NaHCO₃) and magnesium carbonate (MgCO₃) by gastric and pancreatic juice, and exerts its effect as a salt laxative.

Figure 2

Mechanism of hypermagnesemia and milk–alkali syndrome. (a) In patients with impaired renal function, poor magnesium excretion increases the risk of hypermagnesemia. (b) Simultaneous intake of excessive calcium and magnesium oxide, which is a non-absorbable alkali, can increase the serum calcium concentration.

Figure 3

The advantages and disadvantages of magnesium oxide therapy. IBS, irritable bowel syndrome.