Protection by sodium thiosulfate and thiourea against lethal toxicity of cis-diamminedichloroplatinum(II) in bacteria and mice.

The protective effect of sodium thiosulfate and thiourea on the lethal toxicity of the antitumor drug, cis-diamminedichloroplatinum (II) (cis-DDP), was investigated in bacteria and mice. Initially, the agents capable of antagonizing bactericidal activity of cis-DDP were screened using WP2 uvra, a strain of E. coli sensitive to this drug. Of the ten sulfur-containing compounds tested, thiourea and sodium thiosulfate exhibited potent protecting effects against cis-DDP cytotoxicity in bacteria. Propylthiouracil and methimazole showed intermediate levels of such protection, but the other 6 compounds had little or no protective effects. Thiourea and sodium thiosulfate were then subjected to the acute lethal toxicity test in mice to assess their protective activity in vivo. We found that cis-DDP i.v. lethality against mice can be blocked almost completely by excess amounts of thiourea or sodium thiosulfate. Thiourea protected against cis-DDP toxicity with a narrow range among the effective doses, while sodium thiosulfate was protective with a remarkably wide range of effective doses. The effectiveness of sodium thiosulfate was also indicated in experiments in which the LD50 dose of cis-DDP (16 mg/kg) i.p. increased over the level of greater than 200 mg/kg with concomitant administration of sodium thiosulfate i.p.