2025 Volume 58 Issue 4 Pages 215-218
An 82‒year‒old man was prescribed oral tenapanor, a selective Na/H exchanger 3 inhibitor, to manage hyperphosphatemia. Twenty‒eight days after its oral administration was initiated, he presented with diffuse erythema and itching on the trunk, both upper arms, and both thighs, leading to hospitalization. A drug rash associated with tenapanor use was suspected, resulting in its discontinuation. The skin rash had improved by the seventh day of hospitalization. A drug‒induced lymphocyte stimulation test for tenapanor was conducted on the ninth day of hospitalization, which yielded a negative result. Given the rapid resolution of the rash following its discontinuation and absence of symptom recurrence while all other oral medications were continued, tenapanor was considered the most likely causative agent. While this agent has been primarily associated with various adverse gastrointestinal reactions, it is essential to recognize that it may also lead to drug rashes, as noted in this case.
