The concentration of desmethylmisonidazole in human tumours and in cerebrospinal fluid.

The concentration of desmethylmisonidazole (DESMISO) was determined in 60 biopsy samples taken from 13 human tumours and in cerebrospinal fluid (CSF) from 8 patients after oral administration. In comparison with misonidazole (MISO), peak concentrations in plasma were reached at earlier times and half-lives were shorter, so that the area under the curve of plasma concentration with time (AUC) was reduced by 45%; the AUC of CSF concentration with time was reduced by 67%. Between 1 and 2 h after administration of DESMISO, concentrations in tumours were generally 85-90% of those of MISO estimated approximately 4 h after it was given. The two drugs when tested in equimolar concentrations have been found in laboratory experiment to be equally potent as hypoxic cell radiosensitizers. Recognizing the lower mol. wt of DESMISO and the trend to higher concentrations in the more necrotic areas of the tumours studied equal doses by weight of the two drugs given orally may give equal radiosensitization of hypoxic cells in human tumours.