Off label use of MGSO4 as per MEDSCAPE is as under:
Preterm Labor (Off-label)
Used as a tocolytic to stop preterm labor
Loading dose: 4-6 g IV over 20 minutes; maintenance: 2-4 g/hr IV for 12-24 hours as tolerated after contractions cease
Do not exceed 5-7 days of continuous treatment; longer treatment duration may lead to hypocalcemia in developing fetus resulting in neonates with skeletal abnormalities related to osteopenia