Abstract
Hyponatremia is commonly reported after the use of proton pump inhibitors (PPI). While omeprazole is most likely to cause hyponatremia, almost all the PPIs have been reported to cause hyponatremia. The underlying mechanism of PPI-induced hyponatremia is a syndrome of inappropriate antidiuretic hormone (SIADH) secretion which leads to hyponatremia. The hyponatremia can develop with only a few days of exposure to PPI. We present a case of a 56-year-old previously healthy female who was prescribed omeprazole for trivial acid reflux symptoms when she presented to the emergency room for evaluation of generalized weakness. She was discharged home from the emergency room after clinical evaluation as she had essentially normal lab work including a negative COVID PCR test. She subsequently developed progressive weakness of extremities and slurred speech over the next three days. She returned back to the emergency room and was found to have profound hyponatremia with MRI evidence of acute disseminated encephalomyelitis (ADEM). She was treated with hypertonic saline to correct hyponatremia and omeprazole was discontinued. The patient also received pulse dose steroids with improvement in her symptoms.