Suspected retention of magnesium oxide tablets during co-administration with recovery K5, a concentrated oral enteral nutrition formula, supported by in vitro disintegration testing

Background Concentrated oral enteral nutrition (EN) formulas are used when adequate energy intake is required despite limited feeding volume, but their compatibility with tablets has not been fully evaluated. We observed computed tomography (CT) findings suggestive of gastrointestinal retention of magnesium oxide (MgO) tablets in an older inpatient receiving concentrated EN and performed an exploratory in vitro disintegration study. Methods Clinical medication, nutrition, and CT data were reviewed retrospectively. The CT attenuation and diameter of intraluminal tablet-like structures were compared with those of an intact MgO tablet scanned in water. For in vitro testing, MgO tablets were evaluated using Japanese Pharmacopoeia-based disintegration testing in purified water, simulated gastric fluid, and simulated intestinal fluid, with or without 30-min pre-exposure to Recovery K5, a concentrated oral EN formula. Direct disintegration in Recovery K5 was also examined as a worst-case condition. Results were summarized descriptively. Results CT showed three discrete high-attenuation intraluminal structures measuring 9.0–9.4 mm and 501–880 HU, findings compatible with suspected undisintegrated MgO tablets. Without pre-exposure, MgO tablets disintegrated within 8–10 s. After pre-exposure to Recovery K5, mean disintegration times increased to 338.5–422.2 s. In Recovery K5 itself, tablets remained incompletely disintegrated beyond 10,020 s. Conclusions This brief report does not establish definitive causality, but it identifies a clinically relevant signal supported by in vitro evidence. These findings support pharmacist-led review of the actual administration sequence, water volume, and dosage-form selection when MgO tablets are administered concomitantly with Recovery K5, a concentrated oral EN formula.