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The standard intravenous (Zuspan) loading dose for seizure prophylaxis in pre-eclampsia is 4 g of magnesium sulfate. Because 50 % MgSO₄ contains 0.5 g/ml, 4 g equals 8 ml, which is typically diluted with 12 ml normal saline (total 20 ml) and infused over 5–15 min [Lu & Nightingale, 2000, PMID 10803454; Sibai et al., 1981, PMID 7465124].