Bouida W, et al. - Researchers performed a randomized, controlled, double-blind clinical trial in three university hospital Emergency Departments (EDs) between August 2009 and December 2014 to assess the benefit of two different doses magnesium sulfate (MgSO₄) compared to placebo in rate control of rapid atrial fibrillation (AF) managed in the ED. They randomized patients > 18 years with rapid AF (>120 beats/min) to receive 9 g of intravenous MgSO₄ (high-dose group, n = 153), 4.5 g of intravenous MgSO₄ (low-dose group, n = 148), or serum saline infusion (placebo group, n = 149), in addition to atrioventricular (AV) nodal blocking agents. Outcomes support the synergistic effect of intravenous MgSO₄ when was combined with other AV nodal blockers which resulted in improved rate control. They noted similar efficacy with 4.5 and 9 g of MgSO₄. However, more side effects were evident in association with a dose of 9 g.