Exploratory Study of Pharmacists’ Monitoring Methods Based on Left Ventricular Function for Hypermagnesemia by Magnesium Oxide in Heart Failure

Serum magnesium (Mg) monitoring in patients with heart failure (HF) receiving magnesium oxide (MgO) is not adequately performed. Furthermore, the relationship between left ventricular function (LVF) and hypermagnesemia in HF is unknown. Here, we investigated the efficacy of serum Mg monitoring by protocol-based pharmaceutical management (PBPM) and the effect of LVF on hypermagnesemia. This protocol is for patients with an estimated glomerular filtration rate of <45 mL/min, receiving MgO, and admitted to the cardiology unit. The pharmacist includes the measurement of Mg when a blood test is ordered for a patient by their physician. Rates of serum Mg measurement and hypermagnesemia detection were compared at 2 years pre-PBPM (n = 88) and at 2 years post-PBPM (n = 55). LVF parameters and reported factors for hypermagnesemia were selected as explanatory factors on multivariate logistic regression. The measurement rate of serum Mg concentration significantly increased from 19.3% pre-PBPM to 80.0% post-PBPM (P < .001). The detection rate of hypermagnesemia also increased from 3.4% to 27.3%, respectively (P < .001). Our results suggest that serum Mg monitoring by PBPM may contribute to the early detection of hypermagnesemia and prevent its progression in HF. According to logistic regression, the adjusted odds ratio for hypermagnesemia with an exacerbation of HF was 9.57 (95% confidence interval: 1.594-57.477, P = .014), and the E/e' > 15, an index of reduced left ventricular diastolic capacity, was 6.46 (95% confidence interval: 1.291-32.364, P = .023). We propose that serum Mg monitoring should be performed during exacerbations of HF in patients with left ventricular diastolic dysfunction, with a pharmacist's assistance.