Convulsive Seizure Due to Hypomagnesemia Caused by Short-term Vonoprazan Intake

A 71-year-old woman was admitted for the treatment of diffuse large B-cell lymphoma of the ileum. She had been taking lansoprazole but was switched to vonoprazan due to epigastric discomfort. Three weeks after starting vonoprazan intake, she had a convulsive seizure, and a blood test showed hypomagnesiemia. The cause of hypomagnesemia was considered to be malabsorption of magnesium from the intestinal tract associated with vonoprazan. After discontinuation of vonoprazan, the magnesium level quickly recovered, and the seizures did not relapse. It is important to consider the risk of hypomagnesemia in patients taking vonoprazan, even for a short period of time.