Polyethylene glycol as a protector against head and neck irradiation

Mice injected i.p. with polyethylene glycols (PEG) 20 min prior to head and neck X irradiation with 1650 rad showed improved survival, increased food and water consumption, and retention of body weight compared with irradiated controls. The LD 50/15 for PEG-treated mice was 1900 +/- 108 rad compared to 1527 +/- 56 for the controls. PEG of molecular weights 200, 400, and 600 afforded significant levels of radioprotection; PEG of molecular weights 1000, 1450, 4000, and 20,000 when given at maximum tolerated doses (approximately 0.5 LD 50) did not. The degree of radioprotection by PEG with molecular 400 given 20 min before irradiation increased with dose up to the maximum tolerated dose of 6.4 g/Kg. Significant, but lower, levels of radioprotection were observed when the PEG was given 5 min after irradiation. Mice injected i.p. with PEG, cystamine, 5-thioglucose, chlorpromazine, polyethylene glycol monomethyl ether or polyvinylpyrrolidone all had comparable survival levels. Polypropylene glycol, polyethylene glycol diacrylate, and polycaprolactonediol were more toxic than PEG and showed no radioprotection.