Magnesium sulfate heptahydrate 50% w/v (2 mmol Mg2+ in 1 ml). Each 2 ml ampoule contains 4 mmol Mg2+ (equivalent to 1 g magnesium sulfate heptahydrate). 

Disclaimer: Magnesium Sulfate Injection is a prescription-only medication to be used as directed by the prescribing medical professional.