A systematic review and meta-analysis of observational studies examined the risk of hypomagnesemia, defined in various studies as serum magnesium levels of 1.6, 1.7, or 1.8 mg/dL.1 Two cohort studies, one case-control study, and 6 cross-sectional studies met inclusion criteria; 115,455 patients were enrolled. The studies were significantly heterogeneous (I2=89.1%), because of varying study designs, population sizes, and population characteristics.
PPI use increased the risk of hypomagnesemia (pooled odds ratio [OR]=1.5; 95% confidence interval [CI], 1.1-2.0) after adjustment for possible confounders such as use of diuretics.
Risk rises with long-term use, but severe hypomagnesemia is rare
Two more recent cohort studies produced conflicting results. Of 414 patients in a managed care cohort who received long-term PPIs, only 8 had mild hypomagnesemia (1.2-1.5 mg/dL) on nearly 14% of their combined 289 measurements. At final measurement, all patients had normal serum magnesium levels.2
A cross-sectional analysis of data from a retrospective cohort analysis of 9818 patients in the Netherlands found that any PPI use during the previous year was associated with an increased risk of hypomagnesemia (serum magnesium <1.73 mg/dL) compared with no use (adjusted OR=2; 95% CI, 1.4-2.9).3 The risk was greatest with use longer than 182 days (OR=3.0; 95% CI, 1.7-5.2). As with studies included in the meta-analysis, this study examined laboratory values exclusively. Only 3 of 724 PPI users had a serum magnesium level below 1.2 mg/dL, the point at which symptoms usually occur.
Case-control studies produce conflicting results
Two recent case-control studies also produced conflicting results. The first compared 154 outpatients who used PPIs for at least 6 months (mean, 27.5 months) with 84 nonusers.4 No association was found with hypomagnesemia (2.17 mg/dL vs 2.19 mg/dL), and none of the patients had a serum magnesium level below 1.7 mg/dL. The control group was poorly defined, however, and the study excluded patients taking diuretics.
Conversely, a study that compared 366 patients hospitalized with a primary or secondary diagnosis of hypomagnesemia (determined from an insurance claims database and defined as the presence of ICD-10 codes for hypomagnesemia or magnesium deficiency) with 1464 matched controls found that hospitalized patients with hypomagnesemia were more likely than controls to be current PPI users (adjusted OR=1.4; 95% CI, 1.1-1.9).5 Whether hypomagnesemia was the cause of the hospitalizations or an incidental finding wasn’t clear.
Concurrent use of diuretics and loop diuretics can increase risk
In a subgroup analysis of the second case-control study, PPI users who also used diuretics had an increased risk of hypomagnesemia (adjusted OR=1.7; 95% CI, 1.1-2.7) compared with patients who weren’t taking diuretics (adjusted OR=1.3; 95% CI, 0.8-1.9).5
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