Adrenal Suppression From Mucosal Absorption of Dexamethasone Mouthwash.

We present an unusual cause of reversible secondary adrenal insufficiency in a breast cancer patient receiving immunotherapy: systemic absorption of a dexamethasone mouthwash used to "swish and spit," without being swallowed, which resulted in elevated serum dexamethasone concentrations. Most such patients are presumed to have permanent adrenal insufficiency - well recognized as a complication of immunotherapy - and committed to life-long exogenous glucocorticoid treatment. Recognition of the potential for such oral mucosal steroids to be systemically absorbed, which might be more common than recognized, is critical for the avoidance of inappropriate management in immunotherapy patients.