Pharmacokinetic Studies of Orally Administered Magnesium Oxide in Rats

Magnesium Oxide in Constipation

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.

The Combined Effects of Magnesium Oxide and Inulin on Intestinal Microbiota and Cecal Short-Chain Fatty Acids

Constipation is a common condition that occurs in many people worldwide. While magnesium oxide (MgO) is often used as the first-line drug for chronic constipation in Japan, dietary fiber intake is also recommended. Dietary fiber is fermented by microbiota to produce short-chain fatty acids (SCFAs). SCFAs are involved in regulating systemic physiological functions and circadian rhythm. We examined the effect of combining MgO and the water-soluble dietary fiber, inulin, on cecal SCFA concentration and microbiota in mice. We also examined the MgO administration timing effect on cecal SCFAs. The cecal SCFA concentrations were measured by gas chromatography, and the microbiota was determined using next-generation sequencing. Inulin intake decreased cecal pH and increased cecal SCFA concentrations while combining MgO increased the cecal pH lowered by inulin and decreased the cecal SCFA concentrations elevated by inulin. When inulin and MgO were combined, significant changes in the microbiota composition were observed compared with inulin alone. The MgO effect on the cecal acetic acid concentration was less when administered at ZT12 than at ZT0. In conclusion, this study suggests that MgO affects cecal SCFA and microbiota during inulin feeding, and the effect on acetic acid concentration is time-dependent.

Influence of oral magnesium-containing supplement and antacid administration on hypomagnesemia induced by panitumumab

PURPOSE

Hypomagnesemia is a common side effect of panitumumab. The effect of magnesium-containing supplement as a laxative and concomitant antacid (proton pump inhibitor and histamine H₂ antagonist) administration on panitumumab-induced hypomagnesemia was retrospectively investigated.

METHODS

Patients with advanced or recurrent colorectal cancer who received panitumumab were included in this study. Serum magnesium levels were extracted from the electronic medical records of 1753 administrations in 221 patients who received panitumumab. Serum magnesium levels in patients with or without oral magnesium-containing supplement and antacid treatment were compared using analysis of covariance as the number of panitumumab administration up to 16 times for covariates.

RESULTS

The mean serum magnesium levels were significantly decreased with increasing number of panitumumab administrations (2.13 mg/dL at 1st vs. 1.55 mg/dL at 16th, p < 0.001). The use of oral magnesium-containing supplement significantly inhibited the decline in mean serum magnesium level (1.98 mg/dL vs. 1.78 mg/dL, p < 0.001). However, antacid use in patients receiving oral magnesium-containing supplement significantly decreased the effectiveness of the magnesium supplement on serum magnesium level (2.02 mg/dL vs. 1.93 mg/dL, p < 0.05).

CONCLUSION

The use of oral magnesium-containing supplement might function as magnesium supplement based on the finding that use of oral magnesium-containing supplement during panitumumab administration decreased hypomagnesemia. However, combination of antacid decreased the supplemental effect of oral magnesium on hypomagnesemia. These results suggest the possibility that use of antacids during anti-EGFR antibody administration may promote hypomagnesemia.