Proton-pump inhibitor-induced severe hypomagnesemia presenting with seizure and functional hypoparathyroidism: A diagnostic challenge in long-term acid suppression therapy

Proton-pump inhibitors (PPIs) are popular drugs used to treat acid-related disorders. The PPIs, though effective and relatively safe, have been linked to clinically significant hypomagnesemia with long-term use, which causes potentially life-threatening complications. A 68-year-old male with an 8-year history of omeprazole 40 mg/day use presented with a generalized tonic-clonic seizure and neuromuscular irritability. Laboratory tests showed severe hypomagnesemia (0.32 mmol/L), hypocalcemia (corrected calcium 1.62 mmol/L), hypokalaemia (3.2 mmol/L), and low parathyroid hormone (12 pg/mL). 24-h urine magnesium was low (12 mg/day), suggesting external magnesium loss. Serum Vitamin D levels and renal function tests were within normal limits. Electrocardiography showed Corrected QT (QTc) interval prolongation (510 ms) with ventricular ectopy. Magnesium levels failed to normalize despite intravenous replacement until omeprazole was discontinued and replaced with famotidine. PPI-induced hypomagnesemia should be suspected in patients on long-term therapy presenting with electrolyte disturbances, seizures, or arrhythmias. Recognition is crucial, as correction is often refractory until the offending drug is withdrawn.