Background: Mannitol is present in the Ethyol ^® (the trade name of amifostine) as an excipient. The mechanism of radioprotection of amifostine is radical scavenging. Since mannitol is another known radical scavenger, we studied the probable additive or synergistic effect of mannitol on the effect of amifostine.

Material and Methods: Mice were irradiated with Co-60 γ -ray in the presence 400mg/kg mannitol alone or in combination with 400mg/kg amifostine. Survival of mice was assessed within 30 days after irradiation (LD 50/30). Moreover, the protective effect of drugs was evaluated using micronuclei (MN) assay. Slides were prepared using femoral bone marrow flush and stained in May-Giemsa. The frequency of MN was determined in polychromatic erythrocytes (PCE) for each sample.

Results: Similar LD50/30 was observed for irradiated mice in the presence of amifostine alone or in combinations with mannitol. High frequency of MN was produced by 3 Gy γ -rays. Amifostine reduced radiation induced MN dramatically, but mannitol had no effect on γ -rays induced MN. Combination of mannitol with amifostine did not change the effect of amifostine alone.