The fate of [14C]-mesna in the rat.

[14C]-Mesna (sodium 2-mercaptoethanesulphonate) has a short serum t1/2 (about 16.5 min) and is excreted in the urine. Within 24 h approx. 77% of the administered dose appeared in the urine. It is bound to serum albumin and immunoglobulins. Total serum protein binding is about 9.7% of the total amount present in serum. [14C]-mesna + [14C]-dimesna (bis[2-mercaptoethane sulphonate]) are present in the blood stream, and so are found in the body organs at low concentration, however, localisation of radioactivity occurs in the kidneys. The binding of [14C]-mesna to proteins and the localisation of [14C]-mesna or [14C]-dimesna in the kidneys are discussed in the context of the cell killing efficacy of the oxazaphosphorines.