title: Relationship between renal function and serum magnesium concentration in elderly outpatients treated with magnesium oxide.
abstract: OBJECTIVE
  We investigated the relationship between renal function and serum magnesium concentration in elderly patients treated with magnesium oxide (MgO) in an outpatient setting of an urban hospital in Japan.
  
  
  METHODS
  In the present study, 44 elderly outpatients (23 patients with constipation treated with daily oral MgO and 21 untreated patients in the control group) who visited Kameyama municipal medical center were enrolled. Variables were age, sex, weight, height, serum magnesium concentration, serum blood urea nitrogen level, serum creatinine level, use of other magnesium-containing supplements and symptoms associated with hypermagnesemia. We calculated the estimated glomerular filtration rate (eGFR) and classified patients based on eGFR category.
  
  
  RESULTS
  Compared with the control group, the MgO group showed a significantly higher concentration of serum magnesium (median 2.2 mg/dL [interquartile range 2.1-2.3] vs 2.4 mg/dL [2.2-2.6], P < 0.001). Hypermagnesemia (>2.6 mg/dL) was noted only in the MgO group. However, symptoms associated with hypermagnesemia occurred in patients from both groups, with no significant difference between groups. In the MgO group, significant difference was seen in the median serum magnesium concentration between eGFR categories (P < 0.05). The category G4 (eGFR 15-29 mL/min/1.73 m(2) ) group had the highest serum magnesium concentration in the MgO group (3.0 mg/L [2.9-3.1]).
  
  
  CONCLUSIONS
  Elderly patients treated with MgO have higher serum magnesium levels compared with the control group. MgO should be prescribed with caution in patients with low renal function as shown by a GFR category G3b or less (eGFR < 30 mL/min/1.73 m(2) ). Geriatr Gerontol Int 2016; 16: 600-605.
authors.affiliation: Department of Internal Medicine, Kameyama Municipal Medical Center, Kameyama, Mie, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Horibata
authors.affiliation: Department of Nephrology, Murase Hospital, Suzuka, Mie, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Tanoue
authors.affiliation: Department of Cardiology and Nephrology, Mie University School of Medicine, Tsu, Mie, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ito
authors.affiliation: Department of Family Medicine, Mie University School of Medicine, Tsu, Mie, Japan.
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Takemura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000553:Ambulatory Care; D000863:Antacids / Q000627:therapeutic use*; D001806:Blood Urea Nitrogen; D016022:Case-Control Studies; D003248:Constipation / Q000097:blood* / Q000188:drug therapy* / Q000503:physiopathology; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007564:Japan; D008274:Magnesium / Q000097:blood*; D008277:Magnesium Oxide / Q000627:therapeutic use*; D008297:Male
chemical_list: D000863:Antacids; D008277:Magnesium Oxide; D008274:Magnesium
keywords: elderly outpatients; estimated glomerular filtration rate; magnesium oxide; serum magnesium concentration