Proton-pump inhibitor-induced severe hypomagnesemia presenting with seizure and functional hypoparathyroidism: A diagnostic challenge in long-term acid suppression therapy.
Yasir Hassan, Gampa Sarjanya, Jegan Duraiswamy et al.
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Case in brief
A 68-year-old man taking omeprazole 40 mg/day for 8 years presented with a generalized tonic-clonic seizure and neuromuscular irritability. Testing showed severe hypomagnesemia (0.32 mmol/L), hypocalcemia, hypokalaemia, and low parathyroid hormone, with low urinary magnesium; vitamin D and renal function were normal. ECG showed QTc prolongation (510 ms) and ventricular ectopy. Magnesium did not normalize with intravenous replacement while omeprazole continued. After it was stopped and replaced with famotidine, the electrolyte disturbance resolved.
What made this case unusual
The severe magnesium depletion was accompanied by low parathyroid hormone and hypocalcemia, with QTc prolongation and ventricular ectopy; replacement remained ineffective until omeprazole was withdrawn.
Diagnostic / clinical pearl
In a patient on long-term PPI therapy with seizures or electrolyte abnormalities, check magnesium and consider the drug as a contributor, particularly when replacement fails to correct the deficiency.