Therapeutic efficacy of sodium nitrite and 4-dimethylaminophenol or hydroxylamine co-administration against cyanide poisoning in rats.

1. The therapeutic efficacy of combined treatment of sodium nitrite (NaNO2) and 4-dimethylaminophenol (DMAP) or hydroxylamine (H2NOH) was investigated in potassium cyanide (KCN) intoxication in male rats. 2. Therapy with NaNO2 (0.27 mmol kg-1) + DMAP (0.09 mmol kg-1) or NaNO2 + H2NOH (0.09 mmol kg-1, produced a protection index (ratio of LD50 of KCN in rats receiving therapy to an LD50 of KCN in rats given only 0.9% saline) of 2.5 and 2.0 respectively. 3. Both the regimens exhibited a beneficial effect in terms of improving the survival time and postural defects in rats exposed to 2 LD50 KCN. 4. NaNO2 + DMAP showed a significant protective effect in the disposition of the plasma cyanide level at different time intervals. 5. The NaNO2 + DMAP regimen was superior to NaNO2 + N2NOH in terms of reactivating the inhibited brain cytochrome oxidase enzyme. 6. The addition of sodium thiosulphate (Na2S2O3) in both the regimens increased the degree of protection. 7. The results suggest that combined therapy with NaNO2 + DMAP could significantly reduce the toxic effects of cyanide, compared with NaNO2+H2NOH treatment.