Alternative dosing regimen of magnesium sulfate for prevention of eclampsia: An observational prospective study

Objective To evaluate serum magnesium concentrations in pregnant women with severe pre‐eclampsia being treated with a novel magnesium sulfate regimen for seizure prevention. Methods This was a prospective, longitudinal study. Pregnant women aged 18 years or older with severe pre‐eclampsia and an indication for treatment with magnesium sulfate were included. Participants received a magnesium sulfate loading dose of 4.5 g over 20 min, then a maintenance dose of 1.5 g/h (the standard regimen at the study center). Serum magnesium concentrations were measured at admission, 30 min, 1, 2, 4, and 6 h, then every 6 h until treatment was stopped. Median (interquartile range [IQR]) serum magnesium concentrations are reported. The primary outcome was serum magnesium concentrations during magnesium sulfate infusion. Results Serum magnesium concentrations at admission and after 30 min were 0.77 (IQR 0.72–0.82) and 1.81 (IQR 1.63–1.97) mmol/L, respectively. After 4 h, the concentration had decreased slightly to 1.79 (IQR 1.58–2.02) mmol/L. By 12 h, magnesium levels had stabilized at 2 mmol/L. At this time, 50.9% (28/55) had achieved therapeutic magnesium levels (2.0–3.5 mmol/L), and this proportion had increased to 61.7% (29/47) by 24 h. Magnesium toxicity was observed in three patients (4.7%). No cases of eclampsia or maternal mortality were recorded. Conclusions This magnesium sulfate regimen was generally well tolerated and also prevented seizures even though serum magnesium levels at 24 h were below the currently defined therapeutic range in at least one‐third of participants.