Delayed Upper Gastrointestinal Motility in Mice Treated with Oral Iron Tablets

Oral iron preparations for iron deficiency anemia have major side effects, such as nausea and vomiting, which are gastrointestinal symptoms widely known to occur with gastrointestinal motility disorders. However, it is unclear whether these symptoms are associated with gastrointestinal motility. This study aimed to explore the correlation between oral iron preparations that cause nausea and vomiting with gastrointestinal motility. Sodium ferrous citrate (SFC), a common ingredient in iron preparations, was used in this study. Gastrointestinal motility in mice was measured using the ¹³C-octanoic acid breath test to determine gastric emptying and colonic transport capacities using the bead expulsion test. SFC significantly delayed gastric emptying. However, it did not affect the colonic transport capacity. Treatment with the antiemetic palonosetron, a 5-hydroxytryptamine 3 (5-HT₃) receptor inhibitor, abolished the gastric evacuation retardation effect of SFC. However, the additive in the SFC formulation, palonosetron alone, did not affect the gastric emptying capacity. These results suggest that iron preparations cause vagal nausea and vomiting in the upper gastrointestinal tract due to chemical stimulation of the gastrointestinal blood with a concomitant reduction in gastric emptying capacity. Knowledge of the association of delayed gastric emptying with the onset of iron-induced nausea is useful for understanding iron-induced adverse effects.