A patient on long-term omeprazole 40 mg daily develops hypomagnesemia, hypocalcemia, and tetany. The mechanism of PPI-induced hypomagnesemia is:

• A Omeprazole inhibits gastric acid, raising gastric pH and precipitating magnesium as Mg(OH)2, preventing its intestinal absorption
• B PPIs impair intestinal magnesium absorption by inhibiting the transient receptor potential melastatin (TRPM6/7) channels in the colon, which are the active magnesium transporters; these channels require an acidic environment to function ✓
• C PPIs increase renal magnesium excretion by inhibiting the H+/K+-ATPase at the cortical collecting duct
• D Long-term PPI use reduces ileal vitamin D-dependent calbindin D9k expression, indirectly reducing magnesium co-transport

Explanation

PPI-induced hypomagnesemia is an idiosyncratic but recognized adverse effect occurring after prolonged use (typically >1 year). The mechanism involves impairment of TRPM6/7-mediated active magnesium transport in the small intestinal and colonic epithelium. These transient receptor potential channels require an acidic luminal environment to maintain functional conformation for Mg2+ import into enterocytes; PPIs, by alkalinizing the GI lumen, impair TRPM6/7 channel function. Passive paracellular Mg2+ absorption (which does not require acid) is insufficient to compensate. Hypomagnesemia causes secondary hypocalcemia and hypokalemia (impaired PTH secretion and release from bone). IV magnesium replacement is required; oral magnesium supplementation is often insufficient because the absorption defect persists with ongoing PPI use.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.