[Proton-pump inhibitor use and hyponatremia]

Proton-pump inhibitors (PPIs) are widely used. However, reports of their adverse effects are increasing. Older patients are prone to developing hyponatremia due to various factors. The special environment of a geriatric healthcare facility tends to subject these patients to long-term medication use. Therefore, we hypothesized that nursing home residents receiving PPIs will present hyponatremia.

The residents of Shonan Silver Garden, a long-term care health facility for older adults, were divided into two groups: a control group (n=61) which did not receive proton-pump inhibitors and a PPI group (n=29), which received proton-pump inhibitors for at least 6 months. The PPI group was further divided into the lansoprazole group (LPZ group) and the other PPI group. Other PPI users were excluded due to small numbers. The blood test results were compared between the control and LPZ groups. In the LPZ group, blood samples were taken 1 month after the discontinuation of lansoprazole, and serum Na level was compared to the level before discontinuation.

Blood Na levels in the PPI were lower than those in the control group, and hyponatremia (<136 mEq/L) was more frequent in the LPZ group than in the control group. There were no significant differences in other blood test parameters between the control and LPZ groups. At one month after the discontinuation of lansoprazole, serum Na levels were significantly increased; however, they remained lower than those in the control group.

A higher rate of hyponatremia was induced in older residents of long-term care facilities who took lansoprazole for >6 months in comparison to those who did not take lansoprazole.