Effect of magnesium hydroxide on iron absorption following simulated mild iron overdose in human subjects

Objective: To determine the effect of oral magnesium hydroxide [Mg(OH)₂] on iron absorption after simulated iron overdose in human subjects. Methods: A randomized, controlled crossover study was conducted in healthy adult male human volunteers taking no medications. Subjects received an average of 5.0 mg/kg elemental iron orally followed 1 hour later by either oral administration of 4.5 g of Mg(OH)₂ per g ingested elemental iron or no treatment. Serial serum specimens were obtained over the 12 hours following iron ingestion and stored at -60°C until standard serum iron assay was performed. After a 2-week washout period, the subjects were enrolled in the alternative trial arm. Individual baseline diurnal variation in serum iron levels was determined over a 12-hour period on the day prior to each trial. Area under time-concentration curves (AUCs) were calculated, and the AUC due to experimental iron ingestion (ΔAUC) was determined by subtracting the baseline diurnal AUC from the experimental AUC for each subject. Results: Thirteen healthy adult male subjects were enrolled. Mean ± SEM for ΔAUC due to experimental iron ingestion followed by treatment with Mg(OH)₂, 78 ± 23 μmol(hr)/L, was significantly less than that followed by no treatment, 144 ± 33 μmol(hr)/L (p = 0.03 by signed rank test). Conclusions: Magnesium hydroxide, administered i hour post-iron ingestion at an oral dose of 4.5 g per g elemental iron ingested, significantly reduced iron absorption during a 12-hour period following simulated mild iron overdose in healthy adult human volunteers.