OS034. Magnesium sulfate for prevention of eclampsia: Are intramuscularand intravenous regimens equivalent?

Magnesium sulfate is the agent of choice for the treatment and prevention of eclampsia. Optimal loading and maintenance dosing has not been determined.

To compare the pharmacokinetic parameters if IM vs. IV magnesium sulfate.

A pharmacokinetic study was performed as part of a randomized trial that enrolled 300 women comparing IM and IV regimens of magnesium dosing in two low resource sites in India. Data from 258 enrolled women were analyzed in the pharmacokinetic study. Due to infrastructure available at the sites, a single sample was drawn per subject with the expectation of utilizing samples in a pooled data analysis.

Magnesium clearance was estimated via pharmacokinetic modeling to be 48.1dL/h, volume of distribution 156dL and IM bioavailability 86.2%. The IM regimen produced higher initial serum concentrations, consistent with a substantially larger loading dose. At steady state, Mg concentrations in the IM and IV Groups were comparable. With either regimen, a substantial number of subjects would be expected to have serum concentrations lower than those generally expected to be therapeutic.

A larger loading dose for the IV regimen should be considered. Where feasible, individualized higher doses of magnesium sulfate would yield a greater number of treated women with clinically effective magnesium concentrations.