Methodological care in the evaluation of the LD50 and of the neutralization of the lethal effect of Crotalus terrificus venom by the plant Peschiera fuchsiaefolia (Apocynaceae)

ABSTRACT

In the present study, we demonstrate that the volumes in which a given protein mass of Crotalus durissus terrificus venom or of a lyophilized stabilized aqueous extract (LSAE) of Peschiera fuchsiaefolia, an antivenom agent injected intramuscularly, have a decisive influence on the results. The LD50 of C. d. terrificus venom injected i.m. in a final volume of 200µg (2µl/g) (saline solution, 0.9 per cent NaCl) was 180µg/100g rat body weight (p<0.05, 161 to 202µ/100g body weight) and the LD50 of the venom injected i.m. in a volume of 50µl (0.5µl/g) was 120µg/100g body weight (p<0.05, 107 to 134µg/100g body weight). The reduction of the final volume injected i.m. also required a reduced mass of LSAE necessary to neutralize the lethal effect of C. d. terrificus venom. The dose of 60mg LSAE/100g rat body weight in a final volume of 200µl administered i.m., 20 seconds after venom injection, and that of 40mg LSAE/100g body weight/200µl mixed and incubated with the venom for 1h at 25º before i.m. injection were able to neutralize the lethal activity of 2LD50. However, the LSAE doses that neutralized the 2LD50 were reduced to 20mg LSAE/100g body weight in a final volume of 50µl when administered i.m. 20 seconds after venom injection and to 2.5mg LSAE/100g body weight/50µl when mixed and incubated for 1h at 25º with the venom i.m. injection. The LD50 of C. d. terrificus venom and the doses of P. fuchsiaefolia LSAE that neutralized the venom lethal activity were, therefore, significantly lower when the final volume injected i.m. was reduced.