Magnesium is the second most abundant cation in the body, and is an essential electrolyte that participates as an enzymatic cofactor. It is absorbed slowly in the intestine. It binds 25 - 30 % to plasma proteins. It is eliminated in urine and feces. It crosses placental barrier, and small amounts pass into breast milk. It is found mainly in nuts, whole grains, and green vegetables. Human requirements are about 200 - 300 mg/day. Magnesium sulfate is a magnesium salt used mainly in magnesium deficiency states and in hypomagnesemias. It also has a saline laxative effect. Topically it has been used in the treatment of certain local inflammations, as in cases of skin pimples. Saturated aqueous solutions are used in baths for the therapy of osteoarthritis and erysipelas.