Endocrine Abstracts

We studied 5 female patients, aged 54–79 years old (mean 70.6 years), on PPI therapy for 2–13 years (mean 8.2 years), who were symptomatic from chronic and sometimes severe hypomagnesaemia (lowest readings 0.36, 0.29, & <0.21 mmol/l in 3 patients) for 7–45 months (mean 29.2 months). Oral magnesium (Mg) supplements were either poorly tolerated or ineffective; and repeated magnesium sulphate infusions (total doses per patient 120–1200 mmol Mg, mean 446 mmol) failed to correct the hypomagnesaemia for more than a few weeks. Patients were switched from PPI therapy (omeprazole 4, esomeprazole 1) to H2 receptor blockers (ranitidine 4, cimetidine 1). The baseline Mg of 0.50 (S.D. 0.10) mmol/l rose significantly to 0.70 (S.D. 0.09) 1 week after PPI withdrawal (paired t-test, t=7.53, P<0.01), and to 0.77 (S.D. 0.03) at week 2 (t=8.04, P<0.01). Serum Mg remained in the normal range at 6 weeks (0.77, S.D. 0.06) and at 12 weeks (0.75, S.D. 0.07, 4 patients). Well-being improved within 1–2 weeks of stopping PPI therapy, but 4 patients suffered troublesome dyspepsia on H2 receptor blocker therapy.

Conclusion: Hypomagnesaemia in patients on PPI therapy corrects rapidly after PPI withdrawal. We presume that PPI-induced acid suppression profoundly inhibits oral Mg absorption in some patients.