2-Mercaptoethanesulfonate-d4 sodium (Mesnum-d4 sodium) is the deuterium labeled Sodium 2-mercaptoethanesulfonate. Mesna (Sodium 2-mercaptoethanesulfonate) is an antioxidant which has cytoprotective effects. Mesna is widely used as a systemic protective agent against chemotherapy toxicity. Mesna is also used to reduce hemorrhagic cystitis induced by cyclophosphamide[1][2].