A Case of Severe Hypomagnesemia with Long-term Use of a Proton Pump Inhibitor Amy Trottier University of Calgary Internal Medicine, PGY1 November 14, 2013 2013 Rocky Mountain/ACP Internal Medicine Conference
Learning Objectives To understand the association between severe hypomagnesemia and use of proton pump inhibitors including the proposed mechanism of action and consequences
Outline An Interesting Case Proton Pump Inhibitors Hypomagnesemia Link to PPI use Consequences Hypothesized Mechanism Key Points
An Interesting Case 70 yo M presented with an episode of decreased LOC at home lasting ~10min Gasp for air Gaze fixed ahead Unresponsive to verbal commands No incontinence, tongue biting, focal neurologic signs, or tonic-clonic activity Fully alert and responsive on arrival to ED
Past Medical History 2005: MI with angioplasty Hypertension Gastroesophageal reflux disease Remote cholecystectomy Smoker Non-drinker Medications Atorvastatin 20mg daily Ramipril 5mg daily Metoprolol 25mg daily Nitroglycerin spray PRN Omeprazole 20mg daily Started in 2005 after MI for gastric protection with dual anti-platelet therapy
Physical Examination Afebrile with stable vital signs Cardiovascular, respiratory, abdominal, and neurological exams all unremarkable upon arrival at the ED Initial labs.
Laboratory Results Measured Value Normal Range Units Sodium 141 133-145 mmol/l Potassium 3 3.3-5.1 mmol/l Creatinine 79 50-120 μmol/l Blood glucose 6.6 3.3-11.0 mmol/l Magnesium 0.26! 0.65-1.05 mmol/l Calcium 1.66 2.10-2.55 mmol/l Albumin 36 33-48 g/l Parathyroid hormone 29 13-54 ng/l Vitamin D 66.8 80-200 nmol/l Fractional Excretion of Mg = 0.11% GI Loss
Clinical Course Omeprazole stopped Substituted with Ranitidine Electrolytes supplemented Investigations: hstn-t, ECG & 24 hr Holter EEG CT head CT PE All negative/ normal
Serum Value (mmol/l) 6 Potassium Supplementation (40 mmol) Calcium Supplementation (500mg) Oral Magnesium Supplementation (10.4 mmol) IV Magnesium Supplementation (2g) 5 4 Potassium 3 2 Calcium 1 Magnesium 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Time (days)
Why is This Important? PPIs are one of the most commonly prescribed classes of medications 65.7 million US prescriptions for omeprazole in 2012 7th most commonly prescribed Nexium (esomeprazole) was the 6th most prescribed drug in Canada in 2010 Over 3.9 million prescriptions Hypomagnesemia can have severe consequences IMS Institute for Healthcare Informatics. 2013. http://static.correofarmaceutico.com/docs/2013/05/20/usareport.pdf (Last accessed Sept 28, 2013). IMS Brogan. 2011. http://www.imshealth.com/deployedfiles/ims/global/north%20america/canada/home%20page%20content/pharma%20t rends/top50dispensed_en_11.pdf (Last accessed Sept 28, 2013).
Consequences of Hypomagnesemia Wide QRS Nonspecific T- wave changes Prolonged QT PVCs Ventricular tachycardia Torsade de pointes Ventricular fibrillation Enhanced digitalis toxicity Weakness Tremor Tetany Carpopedal Spasm Chvostek s and Trousseau s sign Seizures Coma Nausea Anorexia Secondary electrolyte disturbances Hypocalcemia Inappropriately normal or low PTH PTH resistance Hypokalemia Images: http://seksyensatu.blogspot.ca/; http://howshealth.com/hypocalcemia/ http://php.med.unsw.edu.au/embryology/index.php?title=bgdb_gastrointestinal_-_postnatal http://healthmaven.blogspot.ca/2011_07_31_archive.html
PPI Mechanism Acetylcholine Gastrin Inhibit gastric acid release from gastric parietal cells Histamine camp H 2 -R M 3 -R Ca 2+ CCK 2 -R Irreversibly block hydrogen potassium adenosine triphosphatase enzyme system Proton Pump Inhibitors - + + H + H+K+-ATPase K +
Absorption of Magnesium Intestinal Lumen Enterocytes Portal Vein Mg 2+ TRPM6/7* Active transport via saturable TRPM6 & 7 channels Passive paracellular transport (low affinity) *Transient receptor potential cation channel, subfamily M, member 6 & 7
Effect of PPIs on Mg 2+ Absorption PPIs reduce intestinal luminal ph (opposite to effect in the gastric lumen) Decrease ph by 0.5 Inhibition of H + K + -ATPase in the pancreatic duct plasma membrane reduced proton secretion into the interstitium reduced HCO 3 - secretion into the pancreatic duct reduction in ph Bai et al. Molecular Pharmaceutics (2012), 9, 3495 3505.
Effect of PPIs on Mg 2+ Absorption Enterocytes Portal Vein Enterocytes Portal Vein Mg 2+ - TRPM6/7 Mg 2+ - TRPM6/7 - - Without PPI With PPI TRPM6/7 channels contain ionized glutamic and aspartic acid side chains Critical for magnesium absorption Side chain ionization is sensitive to ph
Summary: PPI s and Mg 2+ Absorption Proton pump inhibitors impair intestinal absorption of magnesium via reduced active transport through TRPM6/7 PPIs decrease intestinal luminal ph Reduced fraction of ionized TRPM6/7 channels at lower ph Ionized TRPM6/7 channels critical for transport of Mg 2+ across apical surface of enterocytes
Key Points/Recommendations Consider proton pump inhibitors in your differential for hypomagnesemia It is a rare, though perhaps under recognized, serious adverse effect associated with all proton pump inhibitors Long-term use can cause severe magnesium depletion and secondary electrolyte disturbances For patients starting on a PPI for a long-term course Measure baseline serum magnesium Monitor serum magnesium on an annual basis (or sooner if symptoms develop)
Acknowledgements Dr Paul Gibson Department of Internal Medicine
References M.W. Hess, et al. Systematic review: hypomagnesaemia induced by proton pump inhibition. Alimentary Pharmacology and Therapeutics, 36:405 413, 2012. M. Epstein, S. McGrath, and F. Law. Proton-pump inhibitors and hypomagnesemic hypoparathyroidism. New England Journal of Medicine, 355:1834 1836, 2006. J.P.F. Bai, et al. Modeling and simulation of the effect of proton pump inhibitors on magnesium homeostasis. 1. oral absorption of magnesium. Molecular Pharmaceutics, 9:3495 3505, 2012. IMS Institute for Healthcare Informatics. Declining medicine use and costs: For better or worse? a review of the use of medicines in the united states in 2012, May 2013. IMS Health. Top 50 dispensed medications in Canada, 2010, 2011. UpToDate: A.S.L. Yu and G.K.K. Ahluwalia. Causes of hypomagnesemia. (Topic last updated: May 29, 2013). UpToDate: A.S.L. Yu. Clinical manifestations of magnesium depletion. (Topic last updated: Oct 7, 2013).