A randomized trial comparing the pharmacology of magnesium sulfate when used to treat severe preeclampsia with serial intravenous boluses versus a continuous intravenous infusion.

Background: Magnesium sulfate is the preferred pharmacological intervention for the prevention and treatment of eclamptic seizures in pregnancy. Pain associated with intramuscular injections and the need for an electronic infusion pump for use intravenously represent significant barriers to broader utilization. We hypothesize that an alternative regimen based on serial intravenous (IV) boluses can produce serum concentrations comparable to those produced by a continuous infusion.

Methods: An open-label randomized trial was performed at two hospitals in Egypt. Women with severe preeclampsia were eligible and enrolled between January 2015 and February 2016. Two hundred subjects were randomized by random numbers generated centrally in distinct blocks and stratified by study site. They were assigned to a continuous infusion arm, (4 g loading dose with 1 g/hr. continuous infusion) or a serial IV bolus arm, (6 g loading dose with 2 g bolus every 2 h using a Springfusor® pump). Sparsely sampled magnesium serum concentrations were collected, nonlinear mixed effect modeling was conducted and Monte Carlo simulations were used to generate 200 simulated subjects in each treatment arm. The simulated populations were used to determine area under the concentration-time curve (AUC) as a measure of total drug exposure and compared.

Results: Simulated area under the magnesium serum concentration-time curve was significantly higher in the serial IV bolus arm than in the continuous infusion arm (1107 ± 461 mmol•min /L vs. 1010 ± 398 mmol•min /L, (P = 0.02)). Four percent of women in the serial bolus arm considered the treatment unacceptable or very unacceptable compared to 2% in the continuous infusion arm, (P = 0.68).

Conclusions: Serial IV boluses achieve serum magnesium concentrations statistically significantly higher but clinically comparable to those achieved with a continuous infusion and offer a third option for the administration of MgSO to women with preeclampsia that may reduce barriers to utilization.

Trial Registration: Trial no. NCT02091401, March 17, 2014.