Envenomation of mice by Thai cobra (Naja kaouthia) venom: tolerable venom concentration and exposure time.

Naja kaouthia venom appeared in circulation rapidly after intramuscular injection into mice. The venom concentration attained a maximum level with all doses examined after 20 min. The half value of the maximum level was obtained 1 min after injection when a dose of 4LD50 was used. A critical venom concentration endangering mice was assessed from venom concentration in the sera of mice envenomed with sublethal dose (LD50). A fatal condition was produced within 30 min at a venom concentration of 200-300 ng/ml or within 50 min at a venom concentration of 100-150 ng/ml.