Magnesium oxide tablets form rigid masses in xanthan gum-based thickeners: A physicochemical hazard revealed by a clinical case

Dysphagia, or difficulty swallowing, is a matter of serious concern among older adults. While thickening agents are essential for dysphagia management, they are not pharmacologically inert; their physicochemical interactions with oral medications remain poorly understood and can pose an iatrogenic hazard of mechanical esophageal obstruction. Following a case of acute esophageal obstruction of unknown origin, this study aimed to identify the foreign body, to assess the reproducibility of any disintegration failures across formulations and thickeners, and to examine the systemic barriers that would allow such a hazard to remain unaddressed. This foreign body, a magnesium oxide (MgO) tablet, caused obstruction in a malignant esophageal stricture. It was analyzed using ex vivo computed tomography and chemical analysis. A static immersion model was used to mimic esophageal stasis. The disintegration behaviors of four MgO formulations (n = 6 each) were compared using thickeners (1.0-3.0%) and a pharmaceutical swallowing aid jelly (SA-J). Furthermore, a cross-sectional market survey was conducted in nine regions in Japan to assess the economic barriers to the clinical adoption of SA-J as an alternative swallowing aid. The foreign body was identified as a non-disintegrated, swollen MgO mass. In vitro experiments confirmed a consistent phenomenon observed across all tested formulations: thickeners completely inhibited disintegration in every combination tested, increasing tablet weight by approximately 2.2-fold at concentrations of 2.0-3.0% and forming rigid masses. Conversely, the tablets disintegrated in SA-J in approximately 25 s. The market survey revealed that SA-J costs were approximately 14.5-fold higher per administration than thickeners (p < 0.001). Although based on a single case, these findings highlight that xanthan gum-based thickened water represents a physicochemical hazard that may remain unrecognized in current clinical practice. Choice of swallowing vehicle should be made with full awareness that xanthan gum-based thickeners can prevent the disintegration of MgO tablets.