Researchers from the University of Washington recently published a study in the journal BJOG comparing intravenous (IV) and intramuscular (IM) magnesium sulfate treatment in pregnant women with eclampsia.
The study involved 300 women with eclampsia associated with hypertensive disease. The women were pooled into IV and IM doses. Data was pulled from 258 participants for the final report.
Conclusion: Researchers found an 86.2% bioavailability in IM doses. IM regimens resulted in higher serum concentrations, initially, when larger loading doses were administered. IM and IV levels were comparable at a steady state. Serum concentrations were lower than recommended therapeutic levels in some women, leading researchers to believe individualized dosage would be best in some cases. Researchers also warned that low-dose magnesium sulfate treatment protocols should be approached with caution as they may be ineffective.
Source: Salinger D, Mundle S, Regi A, Bracken H, Winikoff B, Vicini P, Easterling T. Magnesium sulphate for prevention of eclampsia: are intramuscular and intravenous regimens equivalent? A population pharmacokinetic study. BJOG. 2013 Mar 26. doi: 10.1111/1471-0528.12222.