Magnesium sulfate heptahydrate is a hydrate that is the heptahydrate form of magnesium sulfate. It has a role as a laxative and a cathartic. It is a magnesium salt and a hydrate. It contains a magnesium sulfate. MAGNESIUM SULFATE is a small molecule drug with a maximum clinical trial phase of IV (across all indications) that was first approved in 1981 and has 7 approved and 57 investigational indications. Open Targets Epsomite is a mineral with formula of MgS6+O4·7H2O or Mg(SO4)·7H2O. The IMA symbol is Esm. RRUFF Project A small colorless crystal used as an anticonvulsant, a cathartic, and an electrolyte replenisher in the treatment of pre-eclampsia and eclampsia. It causes direct inhibition of action potentials in myometrial muscle cells. Excitation and contraction are uncoupled, which decreases the frequency and force of contractions.